Best printers for Home

Best Mixer Grinder

Best wired Earphones

Best 43 Inch TV in India

Best Wi Fi Routers

Best Home Theatre in India

Smart Watch under 5000

Best Laptops for Education

Best Laptop for Students

As of now no second Covid-19 booster dose is required, said government sources amid an apparent increase in Covid-19 cases.<br />"First we have to complete the booster drive in the country," said the government sources.<br />India's active caseload currently stands at 2,582, with 134 new cases recorded in the last 24 hours, as per <keyword id="83655" type="General" weightage="80" keywordseo="union-health-ministry" source="Orion">Union Health Ministry</keyword> data.<br />As per ministry data, a total of 220.11 cr vaccine doses (95.13 cr <keyword id="7334317" type="General" weightage="80" keywordseo="second-dose" source="Orion">Second Dose</keyword> and 22.41 cr <keyword id="12813770" type="General" weightage="80" keywordseo="precaution-dose" source="Orion">Precaution Dose</keyword>) have been administered so far under <keyword id="10580665" type="General" weightage="80" keywordseo="nationwide-vaccination-drive" source="Orion">Nationwide Vaccination Drive</keyword>.<br /><br /><strong>SEE ALSO:<br /><a target="_blank" class="c-link c-message_attachment__title_link" href="https://www.businessinsider.in/tech/apps/news/series-creators-want-more-money-after-ads-appear-on-netflix/articleshow/96700323.cms">Series creators want more money after ads appear on Netflix</a><br /></strong><a target="_blank" class="c-link c-message_attachment__title_link" href="https://www.businessinsider.in/thelife/news/pope-benedict-xvi-a-man-at-odds-with-the-modern-world-who-leaves-a-legacy-of-intellectual-brilliance-and-controversy/articleshow/96699003.cms"><strong>Pope Benedict XVI: A man at odds with the modern world who leaves a legacy of intellectual brilliance and controversy</strong></a><br />

No second Covid-19 booster dose required: Govt sources

<ul class="summary-list"><li>Millions of people worldwide have had one shot of two-dose COVID-19 vaccines. </li><li><keyword id="44612" type="CITY" weightage="60" keywordseo="Pfizer">Pfizer</keyword> and <keyword id="4912868" type="PERSON" weightage="60" keywordseo="moderna">Moderna</keyword>'s vaccines are likely 80% effective against symptomatic COVID-19 after one dose.</li><li>A single <keyword id="6409874" type="COMPANY" weightage="60" keywordseo="astrazeneca">AstraZeneca</keyword> shot is probably at least 70% effective at preventing symptomatic COVID-19.</li></ul><p>More than <a href="https://covid.cdc.gov/covid-data-tracker/#vaccinations" target="_blank" rel="noopener">183 million Americans</a> and more than <a href="https://coronavirus.data.gov.uk/details/vaccinations" target="_blank" rel="noopener">45 million Britons</a> have received their first dose of a two-shot COVID-19 <keyword id="24209" type="PERSON" weightage="60" keywordseo="vaccine">vaccine</keyword>.</p><p>The US has authorized vaccines from <a href="https://www.businessinsider.com/moderna-coronavirus-vaccine-wins-us-fda-emergency-use-authorization-2020-12" target="_blank" rel="noopener">Moderna</a> and <a href="https://www.businessinsider.com/fda-authorize-pfizer-covid-vaccine-biontech-alex-azar-2020-12" target="_blank" rel="noopener">Pfizer-BioNTech</a>, while the UK has <a href="https://www.businessinsider.com/pfizer-and-biontech-covid-19-vaccines-approved-by-uk-regulator-2020-11" target="_blank" rel="noopener">authorized Pfizer's</a> shot as well as one made by <a href="https://www.businessinsider.com/oxford-astrazeneca-coronavirus-authorized-emergency-use-in-uk-2020-12" target="_blank" rel="noopener">AstraZeneca and Oxford University</a>. Both countries have <a href="https://www.businessinsider.com/expert-panel-recommends-fda-ok-jjs-coronavirus-covid-vaccine-2021-2" target="_blank" rel="noopener">authorized Johnson &amp; Johnson's</a> vaccine, which is a single dose.</p><p>The UK is <a href="https://www.businessinsider.com/should-we-delay-second-vaccine-dose-first-dose-fauci-mutation-2021-2" target="_blank" rel="noopener">delaying the second dose</a> of the vaccines for up to 12 weeks for most people to prioritize giving people their first shot because of an initial shortage of vaccines. In the US, the <a href="https://www.cdc.gov/vaccines/covid-19/info-by-product/clinical-considerations.html" target="_blank" rel="noopener">Centers for Disease Control and Prevention (CDC) has recommended</a> giving second doses of Pfizer's vaccine 21 days after the first, and 28 days after the first for Moderna, with an interval of up to six weeks if "necessary.</p><p>The <keyword id="6355729" type="ORGANIZATION" weightage="60" keywordseo="data">data</keyword> for how well the vaccines work after one dose isn't clear cut - it depends on what you're measuring, and when you're measuring it. Stephen Evans, a professor of medical statistics at the London School of Hygiene &amp; Tropical Medicine and a former drug-safety committee member at the European Medicines Agency, helped Insider break down the data.</p><p>Evans said the Food and Drug Administration (FDA) presentation of the data from late-stage trials of each vaccine was generally the best data available. This is how much protection one shot of each vaccine gives you, based on that data.</p><div type="image" title="Vaccine" height="2082" width="2777" msid="82219588" hostid="261"></div><h2>Pfizer-BioNTech: at least 80%</h2><p>Pfizer's shot was 52.4% effective at protecting against COVID-19 with symptoms between the first and second dose, <a href="https://www.fda.gov/media/144337/download" target="_blank" rel="noopener">according to the FDA documents</a>. But the 52.4% figure includes the 11 days before protection kicks in after the first dose, so the real percentage could well be higher.</p><p>The true value lies between 29.5% and 84.5%, according to the FDA documents. There was a wide range because not many people caught COVID-19 in the trial during this time period.</p><div type="image" title="Professor Stephen Evans" height="1193" width="1193" msid="81471155" hostid="261"></div><p>Pfizer's shot was 100% effective at protecting against hospitalization and death. This was based on a small number though - only four people got severe COVID-19 in the trial after receiving placebo rather than the vaccine.</p><p>Evans said there was "pretty clear evidence" that you get at least 80% protection - and "probably" better than 90% - for Pfizer's vaccine against COVID-19 with symptoms after a single dose. He said you couldn't be absolutely sure what happens after 21 days because it hadn't been fully tested.</p><p>Evans said this was based on his overall reading of the trial data used by the FDA in their briefing document before authorization.</p><h2>Moderna: at least 80%</h2><p>Moderna's vaccine was 69.5% effective at preventing COVID-19 with symptoms between the first and second dose, with a true value between 43.5% and 84.5%. There was a fairly wide range because the number of people that caught COVID-19 in the trial during this time period was low.</p><p>The 69.5% figure includes the 13 days before protection starts, so the real percentage could be higher.</p><p>There were a small number of people in Moderna's trial - about 7%  - that didn't get their second dose for unknown reasons. In this group, the shot was 50.8% effective at preventing COVID-19 with symptoms for up to 14 days after the first dose and 92.1% effective after 14 days.</p><p>It is unclear how well one shot of the vaccine protects against hospitalization and death because not many people got severe COVID-19 - two in the vaccine group and four in placebo. </p><p>Evans said that you get at least 80% protection - and probably better than 90% - for Moderna's vaccine against COVID-19 with symptoms after a single dose for 28 days. After 28 days it was unclear because it hadn't been tested. Again, this was based on his overall reading of the FDA data, he said.</p><h2>AstraZeneca: more than 70%</h2><p>Evans said it was harder to ascertain a figure for AstraZeneca's vaccine because late-stage trials used differing study designs, and a large US study was ongoing. The FDA also has not yet presented the data for the shot in the same way it has done for other vaccines.</p><p>A single dose of AstraZeneca's shot was 76% effective at protecting against COVID-19 with symptoms for at least 90 days, according to late-stage-trial data <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00432-3/fulltext" target="_blank" rel="noopener">published in The Lancet</a> on February 19. The study authors also reported that one dose provided 100% protection against hospitalization, but the numbers were small. </p><p>Based on his reading of existing studies, Evans said the single-dose efficacy for AstraZeneca's vaccine was probably <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00528-6/fulltext-" target="_blank" rel="noopener">at least 70%</a> against COVID-19 with symptoms for the first 90 days. After this time period, it's unclear, he said.</p><h2>Johnson &amp; Johnson: 66%</h2><p><a href="https://www.businessinsider.com/johnson-and-johnson-covid-19-vaccine-arguably-the-best-2021-2" target="_blank" rel="noopener">J&amp;J</a> looked at protection against moderate to severe COVID-19 <a href="https://www.businessinsider.com/fda-expert-panel-recommends-johnson-johnson-coronavirus-vaccine-for-ok-2021-2" target="_blank" rel="noopener">in trials</a>, rather than symptomatic COVID-19, like Pfizer, Moderna, and AstraZeneca.</p><p>Protection kicked in at 14 days and was <a href="https://www.fda.gov/advisory-committees/advisory-committee-calendar/vaccines-and-related-biological-products-advisory-committee-february-26-2021-meeting-announcement" target="_blank" rel="noopener">66.1% effective at 28 days</a>. The vaccine's efficacy varied depending on the country it was used in - it was <a href="https://www.businessinsider.com/jj-single-dose-covid-19-vaccine-full-study-results-2021-2" target="_blank" rel="noopener">72% effective in the US</a> but 64% and 68% effective in South Africa and Brazil, respectively. These countries both have <keyword id="1754604" type="PERSON" weightage="60" keywordseo="coronavirus">coronavirus</keyword> variants circulating that could partially evade antibodies.</p><h2>What percentage efficacy means</h2><p>Percentage efficacy for vaccines refers to the proportion of people that get full protection after a vaccine. With 80% efficacy, 80% of people have full protection, and 20% don't.</p><p>For those who get full protection the first time around, the second shot improves the quality of the immune response and its durability.</p><p>For the people who don't get full protection with the first shot, some will get full protection after the second dose. Some people won't ever get full protection from a vaccine because their immune system doesn't respond at all.</p><h2><strong>The latest real-world data: One shot significantly reduces infections and transmission</strong></h2><ul><li><a href="https://www.businessinsider.com/one-dose-astrazeneca-or-pfizer-vaccine-protects-against-covid-19-2021-4" target="_blank" rel="noopener noreferrer">A UK study</a> found Pfizer or AstraZeneca's vaccine cut COVID-19 infections with symptoms by 72% after one dose, and protection probably held up for 10 weeks. Protection from Pfizer's vaccine rose to 90% after two doses. The study hasn't been peer-reviewed. </li><li>A <a href="https://www.cdc.gov/mmwr/volumes/70/wr/mm7013e3.htm?s_cid=mm7013e3_w" target="_blank" rel="noopener noreferrer">US study</a> of essential workers found that a single dose of Pfizer of Moderna's COVID-19 vaccines were 80% effective against all coronavirus infections from 14 days.</li><li>A <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00677-2/fulltext?utm_campaign=lancetcovid21&amp;utm_content=163707807&amp;utm_medium=social&amp;utm_source=twitter&amp;hss_channel=tw-27013292nnel=tw-27013292" target="_blank" rel="noopener noreferrer">Scottish study</a> found that a single dose of Pfizer's vaccine was 91% effective against hospitalization at 28 to 34 days following vaccination. One dose of AstraZeneca's vaccine was 88% effective against hospital admissions after the same time period.</li><li><a href="https://www.businessinsider.com/one-shot-astrazeneca-pfizer-vaccine-halves-covid-spread-study-2021-4" target="_blank" rel="noopener noreferrer">A UK study</a> found that a single dose of either Pfizer or AstraZeneca's vaccine cut spread of symptomatic COVID-19 within a household by up to 50%.</li><li>A <a href="https://www.businessinsider.com/one-shot-pfizer-astrazeneca-coronavirus-vaccine-effective-south-korea-2021-5" target="_blank" rel="noopener noreferrer">South Korean study</a> found one dose of Pfizer's vaccine was 89.7% effective at preventing COVID-19 in South Koreans aged over 60, at least two weeks after vaccination. AstraZeneca's vaccine was 86% effective at preventing COVID-19 after one dose. The severity of illness that the shots protected against was unclear - generally they're more effective at preventing COVID-19 infections that caused hospitalization or death.</li><li>An <a href="https://www.bmj.com/content/373/bmj.n1088" target="_blank" rel="noopener noreferrer">English study </a>found that a single dose of either Pfizer or AstraZeneca's vaccine was about 80% effective at preventing hospitalization in people over 70-years-old. Protection lasted for at least 6 weeks, including against the Alpha variant first identified in the UK.  </li><li>An <a href="https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2780700?widget=personalizedcontent&amp;previousarticle=0le=0" target="_blank" rel="noopener noreferrer">Israel study </a>showed that Pfizer's vaccine was 54% effective against symptomatic COVID-19, from 13 days to 24 days after vaccination, a figure comparable to the late stage trial data presented to the FDA.</li><li>A <a href="https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(21)00289-9/fulltext" target="_blank" rel="noopener">UK study</a> estimated that a single dose of either Pfizer or AstraZeneca's vaccine was between 56% and 62% effective at preventing COVID-19 infection caused by <a href="https://www.businessinsider.com/coronavirus-variants-uk-south-africa-brazil-us-facts-questions-2021-1" target="_blank" rel="noopener">the Alpha variant</a> in people over 75 years-old, four to seven weeks after the first dose. The severity of illness that the shots protected against was unclear, but probably included asymptomatic infections.</li><li>A <a href="https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(21)00330-3/fulltext" target="_blank" rel="noopener">UK study </a>estimated that one dose of Pfizer vaccine was 79.3% effective at reducing the risk of hospitalization from COVID-19 in people aged over 80. A single shot of AstraZeneca's was 80.4% effective, the researchers said.</li><li>An <a href="https://khub.net/documents/135939561/430986542/RCGP+VE+riskgroups+paper.pdf/a6b54cd9-419d-9b63-e2bf-5dc796f5a91f" target="_blank" rel="noopener">English study</a> found that a single dose of Pfizer or AstraZeneca's COVID-19 vaccines was about 60% effective at preventing symptomatic COVID-19 in people with underlying illness that weaken the immune response. These underlying conditions included diabetes, severe asthma, chronic heart disease, chronic kidney disease, chronic liver disease, neurological disease, blood cancer, and HIV.</li></ul><h2><strong>Newest data suggests second shot provides better protection against variants</strong></h2><p>Real-word data from the <a href="https://www.businessinsider.com/india-variant-pfizer-astrazeneca-covid-vaccine-one-shot-effectiveness-2021-5" target="_blank" rel="noopener">UK posted</a> May 23 by Public <keyword id="6354750" type="UNKNOWN" weightage="60" keywordseo="health">Health</keyword> England showed that Pfizer's and AstraZeneca's COVID-19 vaccines worked better against the variants when two doses were given rather than just one. Both vaccines were 30% effective against COVID-19 with symptoms caused by the Delta variant, first identified in India, three weeks after the first dose. </p><p>This was boosted to between 60% and 88% effectiveness two weeks after the second dose. The two vaccines were 50% effective against COVID-19 with symptoms against the variant first found in the UK, Alpha, three weeks after the first dose. This increased to between 66% and 93% two weeks after the second dose.</p><p>Dr. Anthony Fauci, President Joe Biden's chief medical advisor, <a href="https://www.businessinsider.com/delta-variant-covid-coronavirus-india-fauci-second-shot-dose-2021-6" target="_blank" rel="noopener">said on June 8</a> that getting two doses of COVID-19 vaccines would stop the Delta variant from spreading across the US. In the UK, Professor Deborah Dunn-Walters, chair of the British Society for Immunology COVID-19 Taskforce, <a href="https://www.sciencemediacentre.org/expert-reaction-to-research-letter-looking-at-blood-neutralising-antibody-levels-from-people-vaccinated-with-one-or-two-doses-of-the-pfizer-vaccine-against-different-variants-of-sars-cov-2-including/" target="_blank" rel="noopener">said in a statement</a> on June 4 that two doses of Pfizer's vaccine were <a href="https://www.businessinsider.com/pfizer-covid-19-vaccine-antibody-response-variant-lab-study-2021-6" target="_blank" rel="noopener">"critical for protection"</a> against emerging strains of the virus.</p>

How much protection you get from one shot of the Pfizer, AstraZeneca, and Moderna vaccines, according to the best available data

<ul class="summary-list"><li>Army general Gustave Perna, who oversees the logistics of delivering COVID-19 vaccines to states, said the US will give Americans paper cards reminding them to come back for second doses.</li><li>Vaccines from both <keyword id="44612" type="CITY" weightage="60" keywordseo="Pfizer">Pfizer</keyword> and Moderna, which are awaiting emergency authorized use from the FDA, require two doses. </li><li>Experts previously told Business Insider getting 100% of Americans to show up for a second dose might be tricky.</li><li>The US will begin transporting vaccines to states within 24-hours of an FDA greenlight, Perna said.</li></ul><p>The US government will be giving Americans paper cards reminding them to get second doses of COVID-19 vaccines.</p><p>Army Gen. Gustave Perna, who oversees the logistics of delivering COVID-19 vaccines to states, said federal agents will send ancillary kits that include needles and syringes to doctor's offices and pharmacies that will distribute the vaccines. The kits also include paper cards to serve as reminders for patients to get second doses, he said at a Wednesday briefing. Americans will need to fill out the cards with the date they must go in a for a follow-up visit.</p><p>Perna said states, as well as pharmacies like CVS and Walgreens, will have their own plans to notify citizens of when to get second doses.</p><p>"At the federal level, we have capability and capacity to send second dose messages out only if and when it's in collaboration with state laws, regulations, and policies," Perna said.</p><p>Pharmaceutical giant Pfizer and biotech firm Moderna have filed with the US Food and Drug Administration <a href="https://www.businessinsider.com/coronavirus-vaccine-timeline-when-will-they-get-authorized-shots-start-2020-11">for emergency authorized use</a> of their COVID-19 vaccines. An independent advisory committee will meet on <a href="https://www.businessinsider.com/us-fda-approve-pfizer-vaccine-biontech-covid-uk-mhra-2020-12">December 10</a> and decide whether to recommend the FDA approve Pfizer's vaccine. </p><p><em><strong>Read more:</strong> <a href="https://www.businessinsider.com/insider-pfizer-biontech-historic-coronavirus-vaccine-program-2020-11?r=aa-sub">How the pharma giant Pfizer teamed up with a little-known biotech to develop an effective coronavirus vaccine in record time</a></em></p><p>Both vaccines require two doses for optimal effectiveness. Pfizer's must be taken <a href="https://www.businessinsider.com/pfizer-coronavirus-vaccine-2-shots-2020-11">three weeks</a> after the initial dose, and Moderna's <a href="https://www.businessinsider.com/moderna-coronavirus-vaccine-requires-2-shots-month-apart-2020-11">four weeks</a>. </p><p>Getting 100% of Americans to show up for a second dose might be tricky, experts told <a href="https://www.businessinsider.com/pfizer-coronavirus-vaccine-2-shots-2020-11">Business Insider's Aylin Woodward</a>. Studies show a significant number of women <a href="https://pubmed.ncbi.nlm.nih.gov/21440038/">did not return to get second doses</a> of the human papillomavirus vaccine, which protects against cervical cancer.</p><p>A double-dose of the vaccines means states will need twice as many vials and syringes, which <a href="https://www.businessinsider.com/covid-19-vaccine-experts-warn-glass-vials-planes-storage-shortage-2020-9">might be in short supply</a>. </p><p>If taken correctly, early trial data indicates the vaccines will be highly effective at preventing individuals from getting COVID-19. A <a href="https://www.businessinsider.com/pfizer-says-coronavirus-vaccine-effective-will-submit-to-fda-eua-2020-11">Pfizer</a> analysis of late-stage trial data found its shot is 95% effectiveness in preventing COVID-19, exceeding scientists' expectations. <a href="https://www.businessinsider.com/moderna-coronavirus-covid-vaccine-emergency-use-authorization-fda-2020-11">Moderna</a> said its vaccine was 94.1% effective at protecting against COVID-19.</p><p>The US will begin transporting vaccines to states within 24-hours of an FDA greenlight, Perna said. <keyword id="6354525" type="UNKNOWN" weightage="100" keywordseo="healthcare">Healthcare</keyword> workers and long term care facility residents will receive the <a href="https://www.businessinsider.com/healthcare-workers-long-term-care-residents-recommended-to-get-vaccines-first-2020-12">first doses</a> of the vaccine. </p>

The US will give Americans paper cards to remind them of their second COVID-19 vaccine dose, but will leave further messaging to states and pharmacies

<ul class="summary-list"><li>Johnson &amp; Johnson said a second dose of its COVID-19 <keyword id="11894310" type="UNKNOWN" weightage="60" keywordseo="vaccine" source="Orion">vaccine</keyword> was highly effective in a study.</li><li>Two doses were 94% effective against moderate to severe COVID-19 in US study, it said.</li><li>The company cited data from an unpublished study that hasn't been scrutinized by other experts.</li></ul><p>Johnson &amp; Johnson on Tuesday said a second dose of its COVID-19 vaccine was highly effective against moderate to severe COVID-19.</p><p>The company <a href="https://www.jnj.com/johnson-johnson-announces-real-world-evidence-and-phase-3-data-confirming-strong-and-long-lasting-protection-of-single-shot-covid-19-vaccine-in-the-u-s" target="_blank" rel="noopener">said in a press release</a>, citing its own studies, that two doses provided:</p><ul><li>94% protection against moderate to severe COVID-19 infection in US study;</li><li>74% protection against moderate to severe COVID-19 infection globally;</li><li>100% protection against severe COVID-19 at least 14 days after the second shot.</li></ul><p>The second dose was administered about two months after the first dose, the company said. For context, Moderna's COVID-19 vaccine was given 28 days apart and Pfizer-BioNTech's 21 days apart in trials. There's some evidence that those two shots have worked better in countries, such as the UK, that <a href="https://www.businessinsider.com/delay-second-dose-pfizer-covid-coronavirus-vaccine-immune-response-study-2021-7?r=US&amp;IR=TIR=T" target="_blank" rel="noopener">delayed the second dose</a>.</p><p>The <keyword id="11911199" type="UNKNOWN" weightage="60" keywordseo="jj" source="Orion">J&amp;J</keyword> figures are based on a 30,000-patient study, called Ensemble 2, in which a second dose was given to volunteers 56 days apart, <a href="https://www.statnews.com/2021/09/21/johnson-johnson-says-additional-dose-boosts-covid-vaccine-efficacy/" target="_blank" rel="noopener">STAT News reported</a>.</p><p>To get the top-line figures, J&amp;J said 14 people who received two doses caught moderate to severe COVID-19, compared with 52 people who got the placebo. No one got severe or "critical" COVID-19, the company said.</p><p>The data hasn't yet been published or scrutinized by experts in a peer review.</p><p>Unlike its single-dose shot, a second dose of J&amp;J's vaccine isn't authorized by the Food and Drug Administration.</p><p><a href="https://www.businessinsider.com/moderna-vaccine-protection-covid-hospitalization-compared-pfizer-cdc-study-2021-9">A recent observational study</a> from the Centers for Disease Control and Prevention of patients with no immunocompromising conditions at 21 US hospitals estimated that a single shot of the J&amp;J vaccine reduced the risk of hospitalization from COVID-19 by 71%. It estimated two doses of Moderna's and Pfizer-BioNTech's shots reduced the risk by 93% and 88%.</p>

2nd dose of J&J vaccine boosts protection against moderate to severe COVID-19 to 94% in US study, company says

<ul class="summary-list"><li>A single shot of <keyword id="44612" type="CITY" weightage="60" keywordseo="Pfizer">Pfizer</keyword> or <keyword id="4912868" type="PERSON" weightage="60" keywordseo="moderna">Moderna</keyword>'s vaccine yields high protection for people who've had COVID-19.</li><li>That's probably because their bodies are responding to a viral threat they've seen before.</li><li>One expert said giving people who've had COVID-19 a second dose was "kind of a wasted shot."</li></ul><p>In the race to get <keyword id="1754604" type="PERSON" weightage="60" keywordseo="coronavirus">coronavirus</keyword> vaccines into arms as quickly as possible, scientists think they've found a way to accelerate the process: Give the people who've already had COVID-19 just one dose.</p><p>Most vaccine-eligible Americans are getting either <a href="https://www.businessinsider.com/pfizer-moderna-covid-19-vaccines-comparison-how-the-shots-compare-2020-12">Pfizer's or Moderna</a>'s vaccine, both of which require two doses administered several weeks apart. But a growing chorus of researchers now agrees that a single dose of either vaccine will generate a sufficient immune response among people who've already had the coronavirus. Giving them the second dose, research suggests, might essentially waste a good shot.</p><p>"For those who've been infected and recovered, which is tens of millions of people, they'll only need one shot, which will make the vaccine go even further," Dr. James Hildreth, the president of Meharry Medical College, told Insider.</p><p>Hildreth served on the <a href="https://www.businessinsider.com/live-updates-fda-advisory-committee-moderna-coronavirus-vaccine-2020-12">Food and Drug Administration advisory committee</a> that recommended all three authorized coronavirus vaccines in the US. The third, from <a href="https://www.businessinsider.com/coronavirus-vaccines-compared-pfizer-moderna-johnson-and-johnson-2021-1">Johnson &amp; Johnson</a>, is a one-shot vaccine, so people who've had COVID-19 would get a single dose of that no matter what.</p><p>Given that more than 30 million Americans are known to have had COVID-19, that could be up to 15 million Pfizer or Moderna shots that could go to other people.</p><h2>New research backs up the one-shot strategy</h2><p>Once a person has had COVID-19, their immune system should recognize the virus if it invades a second time. So when a vaccine spurs the body to start producing <keyword id="102007" type="TECHNOLOGY" weightage="60" keywordseo="Antibodies">antibodies</keyword> again, it's logical that the immune system would mount a stronger and quicker defense.</p><p>Indeed, a <a href="https://www.nature.com/articles/s41591-021-01325-6">new peer-reviewed study</a> found similar antibody responses among individuals who'd had COVID-19 and received a single dose of Pfizer's vaccine and individuals who received two doses of the vaccine but had never gotten COVID-19.</p><p>The researchers concluded that "a second vaccine dose did not offer previously infected individuals a substantially greater benefit over a single dose."</p><p>After the first dose, nearly 37% of the study participants who'd had COVID-19 experienced significant side effects versus 25% of study participants who'd never had COVID-19. After the second dose, there wasn't as much difference between the two groups: 51% versus 59%, respectively.</p><p>The researchers found that "fever and chills were more common among previously infected vaccine recipients after the first dose, whereas infection-naive individuals were more likely to experience headache, dizziness, or lightheadedness after the second dose."</p><h2>'The first dose ends up serving as the booster'</h2><div type="image" title="Vaccine" height="2828" width="4800" msid="81865999" hostid="261"></div><p>In a letter in the <a href="https://www.nejm.org/doi/full/10.1056/NEJMc2101667?query=featured_home">New England Journal of Medicine</a> last month, 32 researchers from the Icahn School of Medicine at Mount Sinai wrote that a single-dose strategy for people who'd already had the virus "requires investigation."</p><p>The team found in <a href="https://www.medrxiv.org/content/10.1101/2021.01.29.21250653v1.full.pdf">a small study</a> that people who'd previously had COVID-19 developed 10 to 45 times as many antibodies after their first dose of Pfizer or Moderna's vaccine as the average uninfected person did. The research is still awaiting peer review.</p><p>"The first dose ends up serving as the booster," Dr. Jeremy Faust, an emergency-medicine physician at Brigham and Women's hospital, told Insider. "If you've been infected, it's very likely that one dose would be pretty damn good for quite a while."</p><p>There are a few caveats, though: People may need to confirm that they still have antibodies if they were sick a while ago, since antibody levels wane over time. An antibody test would also be required for those who suspect they had COVID-19 but never tested positive. If that antibody test comes back positive, the second shot is most likely redundant.</p><p>"What is the point?" Akiko Iwasaki, an immunobiologist at Yale University, told Insider. "It's kind of a wasted shot."</p><h2>'This is where the policy lags <keyword id="41551" type="ENTERTAINMENT" weightage="100" keywordseo="science">science</keyword>'</h2><div type="image" title="UK testing antibody" height="2667" width="4000" msid="81441454" hostid="261"></div><p>France in February began <a href="https://www.has-sante.fr/jcms/p_3237456/en/une-seule-dose-de-vaccin-pour-les-personnes-ayant-deja-ete-infectees-par-le-sars-cov-2">recommending a single vaccine dose</a> for people who've had COVID-19.</p><p>By then, the Mount Sinai research was out, and <a href="https://www.medrxiv.org/content/10.1101/2021.01.30.21250843v1">another preliminary study</a> had also discovered high antibody levels among healthcare workers who'd had COVID-19 before receiving their first shot.</p><p>Dr. Mohammad Sajadi, a coauthor of that study, <a href="https://www.businessinsider.com/people-who-had-coronavirus-only-need-one-vaccine-dose-2021-2">told Insider</a> that COVID-19 patients typically develop antibodies about two to three weeks after their initial infection. But the healthcare workers showed high antibody levels a week after their first shot.</p><p>"What that shows you is that individuals who had a prior COVID infection have what we call a recall response or a memory response," Sajadi said. "For most infections, the second time you see that microorganism, you should get a faster response."</p><p>Then in late February, <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00501-8/fulltext">a UK study</a> found roughly equal antibody levels among people who'd received the first dose of Pfizer's vaccine and had never gotten COVID-19 and those who'd had COVID-19 but weren't vaccinated yet. After the people who'd had COVID-19 got their first shot, their antibody levels were 140 times their peak levels before the vaccine.</p><p>Yet most countries, including the US, don't yet recommend a single-dose regimen for people who've had COVID-19.</p><p>"This is where the policy lags science," Iwasaki said.</p><p>Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, <a href="https://www.nbcnews.com/meet-the-press/meet-press-february-21-2021-n1258472">told NBC News in February</a> that the idea was worth considering.</p><p>"The data looked really quite impressive - that if you've been infected and then you get a single dose, the boost that you get with that single dose is really enormous," Fauci said. "That is one thing that you might want to consider, but we really want to look carefully at the data first."</p><h2>Concerns about long-term <keyword id="48619" type="PERSON" weightage="60" keywordseo="Immunity">immunity</keyword></h2><div type="image" title="covid vaccine card cdc" height="2702" width="3911" msid="81441456" hostid="261"></div><p>Since scientists haven't had much time to follow up with vaccine recipients, there's no consensus yet about how long vaccine-induced immunity lasts. This uncertainty is one reason experts are hesitant to advocate anything other than the standard two-dose regimens of the Pfizer and Moderna vaccines.</p><p>Delaying or skipping the second dose places a lot of pressure on the first dose to provide solid, long-term immune protection, Princeton University researchers <a href="https://science.sciencemag.org/content/early/2021/03/08/science.abg8663">wrote</a> Tuesday. They expressed concern that switching up the dosing regimen could lead to a "broad range" of outcomes among vaccinated people.</p><p>But Iwasaki said people who'd had COVID-19 could probably wait months before getting their second shot - if they need one at all.</p><p>"There just isn't any need to do it so early," she said.</p><p>Scientists are also optimistic that even though antibody levels are known to wane over time, T cells will confer long-term protection for those who've had COVID-19. Like antibodies, T cells have impressive powers of recollection that can help the immune system recognize and reattack the coronavirus.</p><p>A recent study found that people who previously had COVID-19 mounted a stronger T-cell response to one shot of Pfizer's vaccine than people who'd never gotten infected did.</p>

The research is in: People who've already had COVID-19 need just one shot

<ul class="summary-list"><li>The <keyword id="6383835" type="ORGANIZATION" weightage="60" keywordseo="delta" source="Orion">Delta</keyword> <keyword id="396427" type="PERSON" weightage="60" keywordseo="variant" source="Orion">variant</keyword> is the most common cause of new COVID-19 infections in the US, the UK, and elsewhere.</li><li>Six studies suggest vaccines from <keyword id="44612" type="CITY" weightage="60" keywordseo="Pfizer" source="Orion">Pfizer</keyword>, <keyword id="4912868" type="PERSON" weightage="60" keywordseo="moderna" source="Orion">Moderna</keyword>, and <keyword id="6409874" type="COMPANY" weightage="60" keywordseo="astrazeneca" source="Orion">AstraZeneca</keyword> work against Delta, to varying degrees.</li><li>These studies cover both symptomatic and asymptomatic COVID-19 infections.</li></ul><p>The <a href="https://www.businessinsider.com/delta-variant-in-us-covid-infections-states-kansas-arkansas-missouri-2021-7" target="_blank" rel="noopener">highly-infectious</a> Delta <keyword id="1754604" type="PERSON" weightage="60" keywordseo="coronavirus" source="Orion">coronavirus</keyword> variant has spread to at least 174 countries worldwide, from the US to <a href="https://www.businessinsider.com/covid-delta-variant-australia-sydney-new-south-wales-lockdown-extended-2021-8?r=US&amp;IR=TIR=T" target="_blank" rel="noopener">Australia</a>, causing a <a href="https://www.businessinsider.com/israel-may-reimpose-coronavirus-restrictions-as-delta-variant-fuels-surge-2021-7" target="_blank" rel="noopener">surge in COVID-19 cases</a>. The variant has mutations that help it partially escape the immune response produced by vaccines.</p><p>The data for how well COVID-19 vaccines work against the Delta variant isn't clear cut. </p><p>The vaccines may offer less protection against symptomatic illness caused by Delta compared to other variants.</p><p>Public <keyword id="11894571" type="UNKNOWN" weightage="60" keywordseo="health" source="Orion">Health</keyword> England said in a report <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1016465/Vaccine_surveillance_report_-_week_36.pdf" target="_blank" rel="noopener">published on September 9</a> that, generally, COVID-19 vaccines were 79% effective against COVID-19 with symptoms caused by Delta after two doses.</p><p>Here's how much protection COVID-19 vaccines give you against symptomatic Delta infections, based on the best available data from four studies.</p><h3><a href="https://www.businessinsider.com/india-variant-pfizer-astrazeneca-covid-vaccine-one-shot-effectiveness-2021-5" target="_blank" rel="noopener">UK study</a>: Pfizer 88% effective, AstraZeneca 67%</h3><p>A UK-based study from May, published in the <a href="https://www.businessinsider.com/pfizer-vaccine-works-against-delta-covid-but-both-shots-needed-2021-7" target="_blank" rel="noopener">New England Journal of Medicine on July 21</a>, found that two doses of either AstraZeneca or Pfizer's vaccine were highly effective against the Delta variant, from two weeks after the second dose. </p><h4>Pfizer</h4><ul><li>33% effective after one dose, 88% effective after two. </li></ul><h4>AstraZeneca</h4><ul><li>33% effective after one dose, 67% effective after two.</li></ul><h3><a href="https://www.medrxiv.org/content/10.1101/2021.06.28.21259420v1.full.pdf" target="_blank" rel="noopener">Canadian study</a>:  Pfizer 87% effective after two doses, Moderna 72% after one dose</h3><p>A Canadian study <a href="https://www.medrxiv.org/content/10.1101/2021.06.28.21259420v1.full.pdf" target="_blank" rel="noopener">posted </a>on Saturday, July 3, found that two doses of a COVID-19 vaccine worked as well against Delta as they did against the Alpha variant, which was previously dominant in the US. </p><p>The study hasn't been scrutinized by experts in a peer-review. </p><h4>Pfizer</h4><ul><li>56% effective from 14 days after first dose, 87% effective after two doses. </li></ul><h4>AstraZeneca</h4><ul><li>67% effective from 14 days after first dose. Not enough data for two doses.</li></ul><h4>Moderna</h4><ul><li>72% effective from 14 days after first dose. Not enough data for two doses.</li></ul><h3>Israel<a href="https://www.businessinsider.com/pfizer-vaccine-appears-less-effective-delta-variant-than-others-israel-2021-7" target="_blank" rel="noopener"> study</a>: Pfizer 64% effective after two doses</h3><p>The Israel Ministry of Health said on <a href="https://www.gov.il/en/departments/news/05072021-03" target="_blank" rel="noopener">Monday, July 6</a>, that Pfizer's vaccine worked slightly less well against the Delta variant than previous estimates. The number of people who got infected during the study period was small, and the figure may have included asymptomatic infections.</p><h4>Pfizer</h4><ul><li>64% effective after two doses. </li></ul><h3><a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)01358-1/fulltext" target="_blank" rel="noopener">Scotland study</a>:  Pfizer 79% effective after two doses, 60% for AstraZeneca.</h3><p>A Scotland-based study published as a letter to the Lancet medical journal <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)01358-1/fulltext" target="_blank" rel="noopener">on June 14</a> found that Pfizer's vaccine offered "very good" protection against the Delta variant. </p><h4>Pfizer</h4><ul><li>79% effective after two doses, at least 14 days after the second dose.</li></ul><h4>AstraZeneca</h4><ul><li>60% effective after two doses, at least 14 days after the second dose.</li></ul><h2>Studies that cover asymptomatic infections</h2><p>Two real-world studies have looked at vaccine effectiveness against all COVID-19 infections, including those that didn't cause symptoms.</p><h3><a href="https://www.medrxiv.org/content/10.1101/2021.08.11.21261885v1" target="_blank" rel="noopener">Qatar study: </a>Pfizer 53.5% effective after two doses, 84.8% for Moderna </h3><p>A Qatari study <a href="https://www.medrxiv.org/content/10.1101/2021.08.11.21261885v1" target="_blank" rel="noopener">posted on August 11</a> looked at vaccine effectiveness against any infection, including asymptomatic infections. It hasn't been scrutinized by experts in a peer-review.</p><h4>Pfizer</h4><ul><li>53.% effective after two doses, more than 14 days after the second dose.</li></ul><h4>Moderna</h4><ul><li>84.8% effective after two doses, more than 14 days after the second dose.</li></ul><h3><a href="https://www.medrxiv.org/content/10.1101/2021.08.18.21262237v1" target="_blank" rel="noopener">UK study:</a> Pfizer 80% effective after two doses, 67% for AstraZeneca</h3><p>A <a href="https://www.businessinsider.com/covid-vaccine-effectiveness-infectious-fully-vaccinated-people-clear-virus-quicker-2021-8?r=US&amp;IR=TIR=T" target="_blank" rel="noopener">UK-based study</a> <a href="https://www.medrxiv.org/content/10.1101/2021.08.18.21262237v1" target="_blank" rel="noopener">posted on August 24</a> examined vaccine effectiveness against any COVID-19 infection, including asymptomatic illness. It hasn't been formally scrutinized by other experts.</p><h4>Pfizer</h4><ul><li>80% effective after two doses, at least 14 days after the second dose.</li></ul><h4>AstraZeneca</h4><ul><li>67% effective after two doses, at least 14 days after the second dose.</li></ul><h2>Why the numbers vary</h2><p>It becomes harder to measure how well vaccines <a href="https://www.businessinsider.com/covid-vaccine-one-shot-effectiveness-pfizer-moderna-astrazeneca-vaccines-dose-2021-3" target="_blank" rel="noopener">work in the real world</a> compared with trials, because you can't control who gets vaccinated and who doesn't. Other differences between the two groups could influence the risk of getting sick from COVID-19. For example, those who chose not to get vaccinated could also be more likely to put themselves in risky situations that may expose them to the virus.</p><p>The numbers can also vary because they depend on other factors, including what you're measuring, when you measure it, the age of the population you're measuring it in, and whether people have had previous COVID-19 infections.</p><p>Stephen Evans, professor of medical statistics at the London School of Hygiene &amp; Tropical Medicine, told Insider that in general, the more severe the illness caused by Delta, the better the COVID-19 vaccines appeared to work against it. But the evidence on vaccines' effectiveness wasn't strong, he said. </p>

How much protection COVID-19 vaccines give you against the Delta variant, according to the best available data

<ul class="summary-list"><li>Experts are split on whether to delay the second dose of COVID-19 vaccines to immunize more people.</li><li>Prioritizing first doses means more vulnerable people get some protection, which could save lives.</li><li>The risk of more <keyword id="1754604" type="PERSON" weightage="60" keywordseo="coronavirus">coronavirus</keyword> mutations could be the price we pay.</li></ul><p>Experts are split on whether governments should <a href="https://www.businessinsider.com/fauci-waiting-for-second-shot-recipe-for-disaster-covid-variants-2021-2">delay the second doses of coronavirus vaccines</a> to ensure that more people get a first shot.</p><p><a href="https://www.nejm.org/doi/full/10.1056/NEJMclde2101987?query=featured_coronavirus" target="_blank" rel="noopener">Countries must decide what to do</a> with their limited <a href="https://www.businessinsider.com/covid-vaccine-questions-cost-side-effects-timeline-2021-1">vaccine</a> stock: Do they immunize more people with a first dose of a two-dose shot, which doesn't give any of them full protection against the coronavirus, or do they hold back doses so that more people complete the <keyword id="24209" type="PERSON" weightage="60" keywordseo="vaccine">vaccine</keyword> course? Central to the debate is how to minimize the risk from <a href="https://www.businessinsider.com/coronavirus-variants-uk-south-africa-brazil-us-facts-questions-2021-1">coronavirus variants</a> that are more contagious than the original virus and threaten to make vaccines less effective.</p><p>So far, most authorized COVID-19 shots in the world are two-dose vaccines. Some experts, <a href="https://www.businessinsider.com/fauci-coronavirus-variant-mutation-2nd-vaccine-dose-covid-2021-1?r=US&amp;IR=TIR=T" target="_blank" rel="noopener">including Dr. Anthony Fauci,</a> the leading infectious-disease expert in the US, fear that delaying second doses risks variants spreading faster. This is because a weaker immune response, from one dose instead of the full two, could nurture variants with mutations that help them survive, they say.</p><p>Variants are a significant concern - but for now a theoretical one, as it has not yet been demonstrated that delaying second shots promotes variants.</p><p>On the other hand, the 2.4 million deaths worldwide from COVID-19 are proof that the risk from coronavirus is <a href="https://www.businessinsider.com/covid-uk-hospitals-nhs-collapsei-doctors-nurses-2021-1">deadly and immediate</a>. Getting people some immunity from the first shot might therefore be a better focus, and some experts are arguing to immunize as many people as possible.</p><h2>UK delays 2nd doses by up to 12 weeks</h2><p>The UK government pioneered the strategy of delaying the second COVID-19 vaccine dose <a href="https://www.gov.uk/government/publications/letter-to-the-profession-from-the-uk-chief-medical-officers-on-the-uk-covid-19-vaccination-programmes" target="_blank" rel="noopener">on December 31</a>, hoping to give some immunity to as many people as possible amid surging numbers of hospitalizations caused by a more contagious variant, called B.1.1.7.</p><p>Brits can get the second dose of the COVID-19 vaccines authorized in the country - one from Pfizer and BioNTech, the other from AstraZeneca and Oxford University - up to 12 weeks after the first dose. The second dose must be the same vaccine.</p><p>Dr. Michael Osterholm, a former COVID-19 advisor for President Joe Biden, has <a href="https://www.businessinsider.com/vaccine-delay-second-dose-first-shot-osterholm-2021-2" target="_blank" rel="noopener">said the US</a> should follow a similar model, prioritizing the first dose and delaying the second. He says this would "reduce serious illness and death" that could occur in the weeks ahead from coronavirus variants.</p><p>In Israel, which is rapidly vaccinating its population, a single shot of Pfizer's vaccine was found to be 85% effective at protecting against symptomatic COVID-19 15 to 28 days after the first shot, <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00448-7/fulltext">according to a study published in The Lancet. </a></p><p>The B.1.1.7 variant, first found the UK, has spread to the US, and the <a href="https://www.cdc.gov/coronavirus/2019-ncov/transmission/variant-cases.html">Centers for Disease Control and Prevention predicts</a> it will become the most common coronavirus variant there by March.</p><div type="image" title="Michael Osterholm" height="1564" width="2878" msid="80771363" hostid="261"></div><p>The CDC has recommended that the second dose of the COVID-19 shots authorized in the US should be given at the intervals tested in trials.</p><p>One, from Pfizer and BioNTech, was tested with the doses 21 days apart, while the other, developed by Moderna, was tested 28 days apart. Both were <a href="https://www.businessinsider.com/coronavirus-vaccines-compared-pfizer-moderna-johnson-and-johnson-2021-1?r=US&amp;IR=TIR=T" target="_blank" rel="noopener">roughly 95% effective</a> at preventing symptomatic COVID-19 in late-stage trials.</p><p>But in "exceptional circumstances," such as when people have forgotten which dose they have received, the CDC says second shots can be given up to six weeks after the first dose.</p><p>The World <keyword id="6354750" type="UNKNOWN" weightage="60" keywordseo="health">Health</keyword> Organization has also recommended a six-week gap "in exceptional circumstances," such as a vaccine shortage. <a href="https://www.politico.eu/article/who-2nd-dose-of-biontech-pfizer-vaccine-can-be-delayed/" target="_blank" rel="noopener">WHO said there was some clinical data that the Pfizer-BioNTech vaccine</a> provided some protection against COVID-19 for up to six weeks from the first dose, so the guidance gives countries leeway to maximize the number of people benefiting from the first vaccine dose.</p><h2>Many experts oppose delaying 2nd doses</h2><p>But <keyword id="3540587" type="PERSON" weightage="60" keywordseo="fauci">Fauci</keyword>, who is President Joe Biden's chief medical advisor, has said <a href="https://www.businessinsider.com/fauci-us-should-prioritize-second-vaccine-doses-2021-2">scientific data favored prioritizing both doses over a single shot</a>. Fauci also said in January that <a href="https://www.businessinsider.com/fauci-coronavirus-variant-mutation-2nd-vaccine-dose-covid-2021-1">delaying second doses could "immunologically select" for virus variants</a>. "It may not be the case, but it gets risky," he <a href="https://www.bloomberg.com/news/articles/2021-01-25/fauci-says-he-s-worried-about-delaying-second-covid-vaccine-dose">said</a>, without elaborating.</p><p>South Africa's most senior vaccine expert, Barry Schoub, <a href="https://www.businessinsider.com/covid-vaccine-second-dose-coronavirus-uk-south-africa-variant-risk-2021-1">said on January 7</a> that the fact coronavirus variants, including one found in South Africa, were more transmissible "would be a motivation to go for the double dose as much as you can." The variant spreading in South Africa has been shown in lab studies to evade antibodies - a part of the human immune system - but <a href="https://www.youtube.com/watch?v=Ja_tLG8CLAc" target="_blank" rel="noopener">researchers have suggested</a> that higher levels of antibodies can still fight against it.</p><p>Lawrence Young, a virologist at the University of Warwick, told Insider that the longer you leave it between doses, "the more people are likely to get infected."</p><p>"They might not get sick, but they could develop vaccine-resistant strains and drive further evolution of the virus," he said.</p><p>Nicole Lurie, professor of medicine and public health offical <a href="https://www.nejm.org/doi/full/10.1056/NEJMclde2101987?query=featured_coronavirus" target="_blank" rel="noopener">said in the New England Journal of Medicine</a> that delaying the second dose could risk public confidence in COVID-19 vaccines if people get infected after having one dose.</p><p>"If these breakthrough cases appear to occur more frequently before the second, delayed dose, confidence will be further compromised, ultimately delaying the end of the pandemic and social and economic recovery," she said.</p><h2>However, the risks from delaying are uncertain</h2><p>The UK's top scientist <a href="https://news.sky.com/story/covid-19-extending-gap-between-coronavirus-jab-doses-creates-small-risk-of-escaped-mutant-variant-whitty-12180180">on January 5 called this</a> a "real worry but quite a small real worry." Chris Whitty, the UK's chief medical officer, said it was a "balance of risk" between getting more people immunized versus encouraging further mutations.</p><p>Jonathan Stoye, an eminent virologist at the Francis Crick Institute, told Insider there was a "danger" of more mutations happening with delaying the second dose - but the magnitude of the danger is unclear. It is not a question of the number of mutations but the types of mutations, Stoye said. "We get a lot of mutations anyway," he said.</p><p>The British approach of delaying the second dose could be especially advantageous for the COVID-19 vaccine developed by AstraZeneca and Oxford, which uses an inactivated chimpanzee virus to stimulate an immune response, because <a href="https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3777268" target="_blank" rel="noopener">trials have indicated</a> a longer gap <a href="http://www.thelancet-press.com/embargo/oxfordvaccineinterval.pdf" target="_blank" rel="noopener">could even produce a better immune response.</a></p><p>Delaying the second dose of messenger-RNA-based COVID-19 vaccines, which use a genetic code to produce an immune response, is more controversial because mRNA vaccines use groundbreaking technology, so we don't know how well they work when the second dose is delayed. Moderna's and Pfizer-BioNTech's shots are mRNA-based. A small study in Israel, which came with caveats, has shown a single dose of the Pfizer-BioNTech shot was <a href="https://www.businessinsider.com/israel-covid-boss-single-vaccine-dose-less-effective-than-hoped-2021-1" target="_blank" rel="noopener">less effective than hoped</a>. </p><p>Both Stoye and Young told Insider that, overall, they agreed with Whitty that the risk of mutations was a tradeoff.</p><p>Stoye said the UK's approach wasn't foolish, as long as people got their second doses.</p><p>Young emphasized the importance of protecting vulnerable people from getting sick and dying. "Even if they're getting partial immunity," he said, "that should be enough."</p><p><em>This article was updated on February 19 with new information about the efficacy of a single shot.</em></p>

Scientists, including Fauci, are facing off over whether to delay 2nd vaccine doses. Here's why the risk of more mutations from delaying shots may ultimately be worth it.

<ul class="summary-list"><li><keyword id="44612" type="CITY" weightage="60" keywordseo="Pfizer">Pfizer</keyword>'s <keyword id="24209" type="PERSON" weightage="60" keywordseo="vaccine">vaccine</keyword> was 54% effective against severe COVID-19 caused by <keyword id="112799" type="PERSON" weightage="60" keywordseo="variants">variants</keyword> after one dose in <keyword id="6355203" type="LOCATION" weightage="60" keywordseo="qatar">Qatar</keyword>.</li><li>Effectiveness against severe COVID-19 rose to more than 90% when two doses were given 21 days apart.</li><li>The results were published in a letter in the New England Journal of Medicine on Wednesday.</li></ul><p>A second dose of Pfizer's two dose COVID-19 vaccine boosted protection against <keyword id="1754604" type="PERSON" weightage="60" keywordseo="coronavirus">coronavirus</keyword> variants including the worrisome variant from South Africa, <a href="https://www.nejm.org/doi/full/10.1056/NEJMc2104974?query=featured_home" target="_blank" rel="noopener">real-world data from Qatar suggests.</a></p><p>The Qatari study, <a href="https://www.nejm.org/doi/full/10.1056/NEJMc2104974?query=featured_home">published as a letter</a> in the New England Journal of Medicine on Wednesday, found that the COVID-19 vaccine co-developed by Pfizer and <keyword id="3124139" type="PERSON" weightage="60" keywordseo="BioNTech">BioNTech</keyword>, was 54% effective against severe illness after one dose and more than 90% effective against severe COVID-19 two weeks after the second dose. Qatar has been giving the shots at 21 days intervals. </p><p>The study authors found that a second dose of Pfizer's vaccine provided strong protection against variants, including against B.1.351, the variant first found in South Africa. Pfizer's <a href="https://www.businessinsider.com/pfizer-biontech-vaccine-south-africa-variant-covid-vaccines-mutation-2021-2" target="_blank" rel="noopener">previous lab experiments</a> have found that antibody's produced by the vaccine didn't work so well against a pseudovirus similar to B.1.351. It wasn't clear how this lab finding would translate into the real-world.</p><p>In the Qatari study, Pfizer's vaccine was 75% effective at preventing infection of varying severity caused by the variant first found in South Africa, called B.1.351, after two doses, and 16.9% effective against B.1.351 infections after one dose.</p><p>The study also adds to a growing body of real-world evidence, including from Israel, that suggests Pfizer's vaccine is highly effective against the highly infectious B.1.1.7 variant, the variant first found in the UK that's commonly found in the US where there are more than 20,000 reported infections across all 50 states,<a href="https://www.cdc.gov/coronavirus/2019-ncov/transmission/variant-cases.html" target="_blank" rel="noopener"> according to the Centers for Disease Control and Prevention (CDC).</a> </p><p>Two weeks after the second dose, Pfizer's vaccine was 89.5% effective at preventing infection of varying severity caused by B.1.1.7, and 29.5% effective against B.1.1.7 infections of varying severity after one dose.</p><h2>The importance of getting the second dose</h2><p>More than 6,000 people of more than 385,000 got a single dose caught coronavirus and five died from COVID-19. While more than 1000 people of more than 265,000 that had two doses got infected and two died from COVID-19, the study authors said. "Nearly all" infections were caused by either B.1.1.7 or B.1.351, they said. </p><p>"[The Qatari data] really strongly emphasizes, with the variants, that need for the second dose," Kathleen Neuzil, professor in vaccinology at the University of Maryland School of Medicine <a href="https://www.washingtonpost.com/health/2021/05/05/pfizer-vaccine-virus-variants/" target="_blank" rel="noopener">told the Washington Post.</a> "Which is a message we've been delivering, but now we have human clinical data to support that message."</p><p><em><strong>Read more: </strong><a href="https://www.businessinsider.com/pfizers-coronavirus-vaccine-2021-timeline-for-children-trials-2021-5" target="_blank" rel="noopener">One slide lays out Pfizer's busy 2021 plans for its COVID-19 vaccine, including when it could start being used in kids</a></em></p><p>The authors did not detail how long after the first dose they tested Pfizer's vaccine. Protection <a href="https://www.businessinsider.com/one-dose-astrazeneca-or-pfizer-vaccine-protects-against-covid-19-2021-4" target="_blank" rel="noopener">after one dose</a> usually kicks in at about 12 days after the first dose and it isn't yet clear how long single dose protection lasts.</p><p>This means it remains unclear exactly how well a single dose of Pfizer's vaccine works against variants.</p><p><a href="https://www.businessinsider.com/one-shot-astrazeneca-pfizer-vaccine-halves-covid-spread-study-2021-4" target="_blank" rel="noopener">Real-world data from the UK,</a> where B.1.1.7 is dominant, found that a single dose of Pfizer's shot cut COVID-19 infections with symptoms by 72%. Protection from a single dose probably holds up for at least 10 weeks, based on measurements of antibody levels, the study said.</p><p>Another real-world study from Scotland <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00677-2/fulltext?utm_campaign=lancetcovid21&amp;utm_content=163707807&amp;utm_medium=social&amp;utm_source=twitter&amp;hss_channel=tw-27013292nnel=tw-27013292" target="_blank" rel="noopener">published in the Lancet</a> on April 23 found that a single dose of Pfizer's vaccine was 91% effective against hospitalization at 28 to 34 days following vaccination, but effectiveness waned after five weeks.</p>

Real-world data from Qatar suggests 2 doses of Pfizer's vaccine are needed against variants

<ul class="summary-list"><li><keyword id="44612" type="CITY" weightage="60" keywordseo="Pfizer">Pfizer</keyword>'s and <keyword id="6409874" type="COMPANY" weightage="60" keywordseo="astrazeneca">AstraZeneca</keyword>'s COVID-19 vaccines seem to work against a variant first found in India.</li><li>A UK study found Pfizer's <keyword id="24209" type="PERSON" weightage="60" keywordseo="vaccine">vaccine</keyword> was 88% effective after two doses and AstraZeneca's was 60%.</li><li>A single dose of either vaccine was 33% effective, highlighting the importance of a second shot.</li></ul><p>The Pfizer-BioNTech and Oxford University-AstraZeneca <keyword id="1754604" type="PERSON" weightage="60" keywordseo="coronavirus">coronavirus</keyword> vaccines are highly effective against the variant first found in India, which is thought to have fueled <a href="https://www.businessinsider.com/india-coronavirus-variant-more-transmissible-who-says-2021-5" target="_blank" rel="noopener">record-breaking infection numbers</a> in the country and <a href="https://www.businessinsider.com/india-hospitals-run-out-of-oxygen-amid-covid-19-surge-2021-4" target="_blank" rel="noopener">overwhelmed its healthcare system</a>, new real-world data indicates.</p><p>The UK study, <a href="https://www.gov.uk/government/news/vaccines-highly-effective-against-b-1-617-2-variant-after-2-doses" target="_blank" rel="noopener">from England's public-health authority</a>, found that two doses of the Pfizer-BioNTech vaccine were 88% effective at preventing symptomatic COVID-19 caused by <a href="https://www.businessinsider.com/coronavirus-variants-uk-south-africa-brazil-us-facts-questions-2021-1" target="_blank" rel="noopener">the variant</a>, which is called B.1.617.2. Two doses of the Oxford-AstraZeneca vaccine were 60% effective, the study found.</p><p>The UK has reported more than 4,000 cases of the variant, which has now spread to 49 countries including the US, according to <a href="https://cov-lineages.org/global_report_B.1.617.2.html">Global Initiative on Sharing Avian Influenza Data</a>. B.1.1.7, a variant first identified in the UK, remains the most common variant both there and in the US.</p><p>One dose offered far less protection, the Public <keyword id="6354750" type="UNKNOWN" weightage="60" keywordseo="health">Health</keyword> England study found. <a href="https://www.businessinsider.com/covid-vaccine-one-shot-effectiveness-pfizer-moderna-astrazeneca-vaccines-dose-2021-3" target="_blank" rel="noopener">A single dose</a> of either vaccine was 33% effective against COVID-19 with symptoms caused by B.1.617.2.</p><p>The study, which was <a href="https://khub.net/documents/135939561/430986542/Effectiveness+of+COVID-19+vaccines+against+the+B.1.617.2+variant.pdf/204c11a4-e02e-11f2-db19-b3664107ac42" target="_blank" rel="noopener">posted as a preprint Saturday</a> and is yet to be peer-reviewed by other experts, is the first in the world to indicate that vaccines offer protection against B.1.617.2, which has mutations that make it highly infectious and might also make it able to escape antibodies produced by vaccines.</p><p>For comparison, two doses of Pfizer's vaccine were 93% effective against symptomatic COVID-19 caused by B.1.1.7, and AstraZeneca's was 66% effective. After one dose, both vaccines were 50% effective against B.1.1.7, the data indicated.</p><p>UK Health Secretary Matt Hancock said <a href="https://www.gov.uk/government/news/vaccines-highly-effective-against-b-1-617-2-variant-after-2-doses" target="_blank" rel="noopener">Sunday in a press release</a> that the findings were "groundbreaking" and showed the importance of getting a second dose to secure the "strongest possible protection" against coronavirus variants.</p><h2>2nd shot of Pfizer and AstraZeneca boosted protection</h2><p>The PHE study adds to a <a href="https://www.businessinsider.com/one-dose-astrazeneca-or-pfizer-vaccine-protects-against-covid-19-2021-4" target="_blank" rel="noopener">growing body of real-world evidence</a> that one dose of COVID-19 vaccines provides some protection against the coronavirus and that protection is <a href="https://www.businessinsider.com/one-dose-astrazeneca-or-pfizer-vaccine-protects-against-covid-19-2021-4" target="_blank" rel="noopener">boosted by the second dose</a>. PHE's <a href="https://www.gov.uk/government/publications/covid-19-vaccine-surveillance-report" target="_blank" rel="noopener">most recent surveillance report</a>, for example, said a single dose of either Pfizer's or AstraZeneca's vaccine was 55% to 70% effective, rising to between 85% and 90% after two doses.</p><p>Adam Kucharski, an associate professor at the London School of Hygiene and Tropical Medicine, <a href="https://twitter.com/AdamJKucharski/status/1396416400412000256" target="_blank" rel="noopener">said on Twitter on Sunday</a> that "first and foremost" the study was "another reminder that second doses matter."</p><p>The amount of protection offered by the vaccines could be more than it seems from the figures, as the PHE researchers did not look at whether the vaccines protected against severe disease caused by variants. COVID-19 vaccines typically offer more protection against these outcomes.</p><p>The lower efficacy of AstraZeneca's vaccine after two doses, compared with Pfizer's, could be down to the fact that it was given mostly to older people, who tend to have weaker immune responses, the study's authors said.</p><p>Other data has <a href="https://www.businessinsider.com/pfizer-vaccine-covid-vaccines-delaying-2nd-dose-shot-boost-antibodies-2021-5" target="_blank" rel="noopener">indicated that AstraZeneca's vaccine</a> can take longer than Pfizer's to reach maximum effectiveness after the second dose.</p>

The Pfizer and AstraZeneca COVID-19 vaccines are highly effective against the variant first found in India, but only if you get both doses, real-world data shows

<ul class="summary-list"><li>"Fully vaccinated" people need not <keyword id="58679" type="COMPANY" weightage="60" keywordseo="Quarantine">quarantine</keyword> if after they are exposed to COVID-19, the <keyword id="6379474" type="ORGANIZATION" weightage="60" keywordseo="cdc">CDC</keyword> said.</li><li>Full vaccination is the point two weeks after getting a second COVID-19 shot.</li><li>The CDC said the benefits of not quarantining outweight the risks of passing on the virus.</li></ul><p>People who have been fully vaccinated will not have to quarantine if they have been exposed to someone with COVID-19, <a href="https://www.cdc.gov/vaccines/covid-19/info-by-product/clinical-considerations.html">according to newly-updated guidance from the CDC</a>. </p><p>The new rules mean people can skip quarantine if they:</p><ul><li>Got the second dose of a <keyword id="24209" type="PERSON" weightage="60" keywordseo="vaccine">vaccine</keyword> more than 2 weeks ago, but less than 3 months ago.</li><li>Experienced no symptoms of COVID-19 since they were exposed. </li></ul><p>Only the Pfizer and the Moderna vaccine are being distributed in the US at the moment.</p><p>People who aren't vaccinated are still supposed <a href="https://www.cdc.gov/coronavirus/2019-ncov/if-you-are-sick/quarantine.html">to quarantine for 14 days</a> after they have been in close contact with someone who has COVID-19.</p><p>Full protection against COVID-19 is reached by the immune system one week after the second dose of the Pfizer vaccine, and two weeks after the second dose of the Moderna vaccine, <a href="https://www.businessinsider.com/how-long-it-takes-covid-19-vaccine-to-work-2021-1">according to Insider's Hilary Brueck</a>.</p><p>The new CDC <keyword id="6505586" type="UNKNOWN" weightage="60" keywordseo="Guidance">guidance</keyword> said that if a single-dose vaccine becomes available, one dose will be enough to skip quarantine after being exposed to someone who might have COVID-19.</p><p>The guidance admitted that it is not yet clear whether someone who has been vaccinated <a href="https://www.businessinsider.com/how-long-it-takes-covid-19-vaccine-to-work-2021-1">could still pass on the coronavirus to someone else</a>. </p><p>However, in their decision, they said that less quarantining is a benefit that outweighs the risk of increased transmission.</p><p>It is not yet clear whether vaccines will protect against new variants of the coronavirus, so people who have been fully vaccinated should continue to wear masks and respect social distancing rules, the CDC said.</p><p>Public health guidelines have continued to change as experts find out more about the virus and how to treat it.</p><p>A study from the agency recently showed that wearing two masks at once, one surgical mask underneath a cloth mask, <a href="https://www.businessinsider.com/cdc-double-masking-makes-masks-50-more-effective-2021-2">improves the protection given by about 50%</a>.</p><p>It is not yet clear whether the vaccines continue protecting against COVID-19 beyond three months after the second dose is taken.</p><p>However, "there is confidence in protection for those 90 days following vaccination", Saskia Popescu, an epidemiologist and infection preventionist at George Mason University in Virginia, <a href="https://www.nbcnews.com/health/health-news/cdc-fully-vaccinated-people-don-t-need-quarantine-if-exposed-n1257336">told NBC news</a>.</p><p>The recommendations will "likely evolve" as we learn more about how long the vaccine protects against COVID-19, Popescu said. </p><p><strong>Read more</strong><em>: <a href="https://www.businessinsider.com/wpp-is-leading-115-million-hhs-fauci-vaccine-ad-campaign-2021-2">All the ad agencies benefitting from HHS's $115 million vaccine education campaign</a></em></p><p>The CDC had previously recommended that people who have recovered from COVID-19 <a href="https://www.cdc.gov/coronavirus/2019-ncov/hcp/duration-isolation.html">don't need to go into quarantine for 90 days</a>. </p><p>The guidance will be reviewed when new data becomes available, the CDC said.</p>

You Searched For "covid 19 vaccine second dose" and got 10 results

No second Covid-19 booster dose required: Govt sources

ANI

How much protection you get from one shot of the Pfizer, AstraZeneca, and Moderna vaccines, according to the best available data

Dr. Catherine Schuster-Bruce

The US will give Americans paper cards to remind them of their second COVID-19 vaccine dose, but will leave further messaging to states and pharmacies

Allana Akhtar

2nd dose of J&J vaccine boosts protection against moderate to severe COVID-19 to 94% in US study, company says

Marianne Guenot

The research is in: People who've already had COVID-19 need just one shot

Aria Bendix,Hilary Brueck

How much protection COVID-19 vaccines give you against the Delta variant, according to the best available data

Dr. Catherine Schuster-Bruce

Scientists, including Fauci, are facing off over whether to delay 2nd vaccine doses. Here's why the risk of more mutations from delaying shots may ultimately be worth it.

Dr. Catherine Schuster-Bruce

Real-world data from Qatar suggests 2 doses of Pfizer's vaccine are needed against variants

Dr. Catherine Schuster-Bruce

The Pfizer and AstraZeneca COVID-19 vaccines are highly effective against the variant first found in India, but only if you get both doses, real-world data shows

Dr. Catherine Schuster-Bruce

New CDC advice says people are exempt from some COVID-19 quarantine rules after a 2nd vaccine dose

Marianne Guenot

Popular Keywords

Buying Guides