Vaccines may not work as well against the coronavirus variant detected in South Africa, so Moderna and Pfizer are upgrading their shots

• COVID-19 vaccines may be less effective against a more infectious version of the coronavirus first found in South Africa.
• New research shows the mutated strain can evade the antibodies developed in response to vaccination or infection with the original version of the coronavirus.
• Moderna said its vaccine probably protects against the variant. But that company and Pfizer are both working on shots to combat the new strain.

A more infectious coronavirus variant detected in South Africa in December can partially evade the defenses current vaccines build in our bodies' immune systems, according to preliminary research published last week.

The study has not yet been peer-reviewed, but it suggests the variant, known as 501Y.V2 or B.1.351, can escape the antibodies developed in response to vaccination or infection with the original version of the virus. That may mean existing vaccines won't provide as much protection, and people who have already been infected with the original version of the virus could get reinfected with the new strain.

Penny Moore, a researcher at South Africa's National Institute for Communicable Diseases and a co-author of the new study, called the mutations in 501.Y.V2 "problematic." Her group's research found that in half of samples studied in the lab, antibodies in the blood of people who'd recovered from COVID-19 were unable to stop the variant.

Moderna announced Monday that its shot still works against the variant. However, blood samples from vaccinated people seemed to generate less of an immune response when exposed to the variant relative to other versions of the virus. That suggests "a potential risk of earlier waning of immunity," the company said.

So Moderna is planning to test a booster shot tailored to protect people against the strain. Pfizer CEO Albert Bourla, too, announced Tuesday that his company is working on boosters to combat coronavirus variants.

The variant can dodge our body's defenses

Antibodies are protective proteins that our immune system makes when it senses a foreign substance, or antigen, in the body. In general, antibodies fight infection by learning to recognize a virus and signaling to the immune system that it should be destroyed. They do that by binding to the invader until it's wiped out. Vaccines are designed to prompt the body to build the same antibodies that would come about in response to an infection.

But if a virus is different enough from others to evade existing antibodies' search-and-destroy mechanisms, it can continue to wreak havoc.

Moore's group set out to see whether antibodies developed in response to the original version of the coronavirus work to protect people from the new variant. The researchers used blood samples from 44 patients who'd recovered from COVID-19 before the 501.Y.V2 variant was detected.

The scientists exposed the blood to the new variant and found that the antibodies in half of the samples were impotent against the strain. Antibodies in the other half of the samples mounted a weakened response.

These results "may foreshadow reduced efficacy" of existing vaccines, the team wrote. They also warned that people who've gotten the original coronavirus may be at risk of reinfections from 501.Y.V2.

Researchers working with Moderna followed a similar process. They used blood samples taken from people that received the company's vaccine during phase 1 of its clinical trials, and exposed the blood to the new variant. They found that the samples infected with 501.Y.V2 developed six times fewer neutralizing antibodies than samples exposed to other variants.

The South African researchers also found that three types of monoclonal antibodies - laboratory-made antibodies designed to target the coronavirus - were ineffective against 501.Y.V2. Doctors have been using monoclonal antibodies to treat patients; the Food and Drug Administration has authorized two such treatments.

Still, Moore said more data is needed to draw firm conclusions about how the variant interacts with antibodies inside the body, especially among people who've been vaccinated. The research did not look at other elements of the immune system, like B cells, which play a critical role in developing new antibodies.

Nathan Grubaugh, an epidemiologist from the Yale School of Public Health, told Insider that it's hard to tell how well laboratory tests translate to reality in the body. A 90% reduction in protection during a lab test "may still mean complete protection in a human," he said.

As the virus mutates, vaccines may need to evolve

The 501Y.V2 variant has a mutation in its spike protein - the part the virus uses to invade cells - that has "been shown to reduce antibody recognition" among people who were previously infected with the original virus or got a vaccine, according to Francois Balloux, the director of the University College London Genetics Institute.

Other mutations in the spike protein contribute to 501.Y.V2's increased infectiousness, the South African researchers said. That could explain why the country has been hit so hard since November. In the last two months, the number of new coronavirus cases per day in South Africa quintupled, from an average of 2,300 to 13,000. It hit a record high of nearly 22,000 cases on January 8, and the country's test-positivity rate doubled in December. By the end of 2020, 501.Y.V2 had replaced almost all other versions of the coronavirus in South Africa.

It has spread to at least 20 countries.

Other strains, like the B.1.1.7 variant found in the UK, have similar mutations in their spike proteins. But a preliminary study from Pfizer-BioNTech found that the company's coronavirus vaccine is effective against B.1.1.7. Moderna announced its vaccine held up well against that variant, too.

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told NBC News' Today that current coronavirus vaccines are considered effective against existing strains.

"However, we really need to make sure that we begin, and we already have, to prepare, if it's necessary, to upgrade the vaccines," Fauci said Monday.

An upgraded vaccine or booster shot could be 'rapidly deployed'

All viruses mutate. Most mutations are inconsequential, but occasionally one appears that undermines the immunity people have acquired from a vaccination or prior infection. The flu, for instance, mutates quickly, which is why we have to get a new flu shot every year, and why flu vaccines aren't 100% effective.

Thee coronavirus mutates slower than the flu. That's why Trevor Bedford, a virologist at Fred Hutch, predicted in April that "it will take the virus a few years to mutate enough to significantly hinder a vaccine." But Bedford didn't know at the time how much the virus would proliferate and how high case numbers would climb; the more chances a virus has to spread (and therefore replicate), the more likely mutations become.

Bedford tweeted January 20 that "the emerging situation can be dealt with through a forthcoming vaccine update."

BioNTech, Pfizer's partner, said it could produce a new vaccine for a COVID-19 variant in about six weeks. Bourla said at Bloomberg's The Year Ahead conference on Monday that the company is working on a process to create booster shots.

Moderna said it will soon start clinical trials to test whether giving people another booster shot of its current vaccine, or a booster shot tailor-made to neutralize the 501.Y.V2 variant, will improve antibody responses.

"I think our technology is very well suited to actually rapidly deploy a vaccine based on the new variant," Tal Zaks, Moderna's chief medical officer, said in a recent presentation at the J.P. Morgan Healthcare Conference.

That's because these mRNA vaccines don't contain dead versions of virus, but rather genetic instructions for the body to make one of the virus' signature proteins internally, thereby triggering an immune response. Tweaking those instructions is an easy switch.

The decision to sign off on a modified vaccine or booster shot would then be up to regulators.

Immunity to a virus isn't all or nothing

Even if the variant does reduce how well current vaccines work, that doesn't mean protection from infection disappears completely, experts say.

"We often talk about immunity as sort of an all-or-nothing thing, but it's not," Jennie Lavine, a postdoctoral biology researcher at Emory University, told Insider.

The ideal level of protection is sterilizing immunity - when "we have such good immunity in the right places that the virus can't even replicate if it gets in," Lavine said.

But there's plenty of middle ground between that and zero immunity. For example, Lavine said, "the virus might be able to replicate some, maybe causes mild pathology, maybe transmits for a day or two instead of five or six days."

She added: "The chances that the new variant is getting us all the way from sterilizing immunity to no immunity is really unlikely."

It also helps that existing vaccines are highly effective against the original virus.

"The Pfizer and Moderna vaccines are 95% effective - that's an extraordinary level of efficacy," David Montefiori, a vaccinologist from Duke University, told CNN. "If it reduces to 90, 80, 70% effective, that is still very, very good and likely to have a major impact on the pandemic."

Andy Dunn, Catherine Schuster-Bruce, and Aria Bendix contributed reporting.

This story has been updated with new information. It was originally published January 21, 2021.