Vaccinated people: Your odds of a COVID 'breakthrough' infection have gone up. That doesn't mean you need to panic.

• Vaccinated people are well protected from severe disease that could be caused by the Delta variant.
• They can catch COVID-19, but their symptoms may be mild, and the risk of transmitting may be low.
• The US is in a precarious position, with a half-vaccinated population.

New York Yankees, Texas wedding guests, and Vegas partygoers are part of an unlucky but growing minority.

They are fully vaccinated people who've got cases of COVID-19, as the more contagious Delta variant spreads quickly around the world.

Their illnesses are a reminder that this pandemic is not over, and we urgently need more shots in arms - globally.

Vaccinated people: A shot does not catapult you into a post-pandemic dream world. Don't be shocked if you go out and socialize unmasked and then later test positive for COVID-19.

It's nothing to fret about too much: If you get a "breakthrough" infection, it may feel like a cold or be completely asymptomatic.

But with the far more contagious Delta variant at play, your odds of infection are up, and you could also hurt others by spreading an infection around.

"Plague amnesia is going to cause a massive crisis in the United States if people want to forget that we are still in the midst of a pandemic," said Charity Dean, a former top-tier official at the California Department of Public Health and a key character in Michael Lewis' new book about the pandemic.

Being vaccinated doesn't mean you're 100% immune to COVID-19

Fully vaccinated people have been given license to party by the Centers for Disease Control and Prevention, which said that people who are fully vaccinated can go maskless indoors pretty much everywhere, even in public spaces. (Almost half of the US is fully vaccinated, the CDC said.)

"This is becoming a pandemic of the unvaccinated," Rochelle Walensky, the director of the CDC, said during a White House briefing on Friday.

That is the CDC's take-home message in a nutshell: If you are vaccinated, this virus is no longer your concern.

But the reality is, now that the Delta variant dominates, everyone's odds of getting sick have ticked up, especially as more people are mask-free as they mingle with other households.

Delta is about twice as contagious as Alpha, which is in turn about twice as contagious as the original virus identified in Wuhan, China. (Public Health England found the Delta variant was 60% more transmissible than the Alpha variant, which was already deemed "50% more transmissible than current variants" by the CDC.)

Fully vaccinated people who've recently said that they tested positive for COVID-19 include Miami County Commissioner Jose Diaz (who'd been working alongside first responders at the Surfside building collapse), reporter Catt Sadler, comedian Gabriel Iglesias, six Texas lawmakers, and the UK Health Secretary Sajid Javid.

Christopher Murray, the director of the Institute for Health Metrics and Evaluation, which the White House has leaned on for COVID-19 projections, told Insider the Delta variant is driving up cases across the US - including among the vaccinated.

"The vaccines, especially for the Delta variant, are better at preventing severe disease and death than they are at preventing infections," Murray told Insider.

Tim Spector, an epidemiologist at King's College London, told Insider there is nothing to suggest Delta is more lethal, but it is more infectious, and "because of that extra stickiness, it's going to still keep breaking through the vaccine group."

The good news is that even with the more contagious Delta variant around, COVID-19 appears to be milder in vaccinated people, who may suffer symptoms such as coughs, headaches, temporary loss of taste and smell, and sore throats. Fully vaccinated people also tend to carry less virus in the back of their nose and throat, meaning they are probably less likely to spread COVID-19 to others, compared to unvaccinated people who are ill.

'It wasn't that bad'

Hilary Young, a branding consultant in Philadelphia who's been fully vaccinated for more than two months, is another person who recently tested positive for COVID-19. She said her symptoms included a mild sore throat, congestion, headache, dizziness, fatigue, insomnia, and the loss of taste and smell.

"My worst fear happened, we survived it, and I think that's a direct result of being vaccinated," she said. "It wasn't that bad for me. I didn't end up in the hospital. I wasn't totally knocked out."

Her story tracks with the data. In the US, unvaccinated people now account for 97% of COVID-19-related hospitalizations, the CDC said.

But many fully vaccinated health experts still remain cautious when they're out and about, knowing they could contract a mild case of the virus.

"I realize I'm not likely to die if infected," Professor Don Milton from the University of Maryland, a leading expert on airborne viruses, recently told Insider, explaining his choice to wear an N95 mask when he goes shopping in suburban Maryland.

"I could still get ill, miss work, screw up my vacation, and [there's] a small risk that I'd have long-term effects. Why take the risk?" he said.

Young agreed.

"I will continue to wear a mask indoors," she said. "I think, at the very least, that's something that people should be encouraged to do - especially if you're at CVS, where people are shopping for what they think is cold medication."

A vaccine doesn't operate like a magic wand

No vaccine has ever been capable of preventing every single case of an illness.

We know this already because each year scientists develop new flu vaccines, which are at best about 60% effective at keeping people flu-free.

Like COVID-19 vaccines, flu vaccines are worth getting because they teach your body how to better fight off future infections, likely making a case of the virus milder if you catch it. Ideally, if enough people get vaccines, the amount of virus circulating in a community would be lower, so that fewer vulnerable people would get sick and die.

Conversely, low vaccination rates, coupled with a far more contagious viral variant such as Delta, put everyone at greater risk of an infection.

So wearing masks and limiting exposure to people who may be infected should still be critical components of communitywide disease prevention. Though it's less likely than it would be if they remained unvaccinated, vaccinated people could also spread COVID-19 to immunocompromised people and to children under 12, as well as their families.

"The bottom line is, we are dealing with a formidable variant in the Delta variant," Anthony Fauci, President Joe Biden's chief medical advisor, said during a White House briefing on Friday. He added that "the message loud and clear that we need to reiterate" is that the vaccines continue to offer "strong protection."

We have to accept that the odds of infection have changed for vaccinated people

The CDC doesn't encourage any of the 160 million vaccinated people across the US who are exposed to COVID-19 to get tested for it, unless they go on to develop symptoms.

Instead, the country relies on data from the UK and Israel to figure out how well COVID-19 can dodge our vaccines.

This puts the US at a disadvantage as the virus continues to morph, doing its best to survive. With Delta around, we know vaccinated people are not as well protected as they once were. Now, we risk missing the signals of a more dangerous variant - something that our existing vaccines would barely combat.

Young is frustrated that the data on her own breakthrough case - which was detected with an at-home test - won't be recorded anywhere by the CDC. Young said her doctor didn't encourage her to seek out confirmation with a laboratory test. Instead they said, "You just have to quarantine, and you should be fine."

Dean said, given the low level of testing and sequencing being done on fully vaccinated people right now, there's no way the US can keep tabs on the virus well enough. If we want to know how decent the vaccine protection of the country really is, Dean said, we need to know when vaccinated people are getting infected, what variant they have, and how severe their case is.

"It's very concerning to me that we're 20 months into the pandemic and we don't have that capability yet," she said. "The technology has to move faster than the pathogen."