In 2020, Covid reinfections were considered rare.
In 2021, breakthrough infections in vaccinated people could occur, but again, the risk was low.
In 2022, that's no longer the case for either. As more immunity-dodging coronavirus variants emerge, reinfections and breakthrough infections appear increasingly normal.
The U.S. isn't tracking Covid reinfections. However, U.K. researchers have found that the risk of reinfection was eight times higher during the wave of the omicron variant than it was in last year's delta wave.
“I would not be surprised if we see people get infected more than once per year,” Dr. Anthony Fauci, President Joe Biden’s chief medical adviser, said in an interview in June, although he added that he was optimistic that it would eventually become just a seasonal occurrence, like the flu. (Fauci, who has received two vaccine booster shots, himself tested positive for Covid the week after the interview, saying he had mild symptoms.)
The risk for reinfection appears even higher now, thanks to two immunity-dodging omicron subvariants, BA.4 and BA.5. Together, they are driving the majority of new cases in the U.S.
Both subvariants are “more transmissible and more immune evading” than previous versions of omicron, the director of the Centers for Disease Control and Prevention, Dr. Rochelle Walensky, said Tuesday at a White House briefing. “People with prior infection, even with BA.1 or BA.2 are likely still at risk for BA.4 or BA.5.”
Of course, just because reinfections are possible doesn’t mean people should give up on all efforts to prevent them; staying up to date on vaccinations and wearing masks indoors in places with high transmission still lower risk.
Here’s what we know so far about reinfections.
Can I be reinfected if I’ve already had Covid or been vaccinated or boosted?
To put it bluntly, yes. Experts agree that reinfections are possible, even in people who have already been infected or those who are up to date on their vaccinations.
“Reinfections, unfortunately, are not unusual for coronavirus,” said Akiko Iwasaki, a professor of immunobiology at Yale University. “It’s just the nature of this virus infection.”
The coronavirus that causes Covid isn’t unique — other types of coronaviruses that cause common colds can also reinfect, Fauci said. But those reinfections may occur every two or three years, because those viruses don’t change very much.
Full coverage of the Covid-19 pandemic
That’s not the case for SARS-CoV-2, and particularly its rapidly evolving omicron subvariants, which are good at evading existing immunity. Combine that with the fact that people’s immunity naturally wanes over time, Iwasaki said, and “it’s not that surprising to see a lot of reinfections now.”
That’s especially true for people who were infected with the original omicron variant, dubbed BA.1, in the winter. The BA.4 and BA.5 subvariants are quite different from BA.1, so “it’s no guarantee” that having a past omicron infection will protect you from subsequent subvariants, she said.
How many times can I be reinfected?
It’s impossible to put an exact number on how many times a person can be reinfected, experts say.
With a high level of Covid spreading in the U.S., any of us has a good chance of being exposed to someone who is contagious — and of becoming reinfected.
Whether people are reinfected depends on the strength of the immune response when they were exposed, as well as whether they have recently been vaccinated, said Dr. Julie McElrath, the director of the vaccine and infectious disease division at the Fred Hutchinson Cancer Center in Seattle. Multiple exposures to the virus — which may not necessarily lead to symptoms — could have a silver lining, McElrath said.
Every time a person is exposed, the immune response matures and improves.
“We should consider reinfection as part of the new normal,” she said. “The hope is that with these multiple exposures, continually improving antibody response will occur.”
How long does Covid immunity last after infection?
Whether a person is less susceptible to reinfection in the weeks after an infection hasn’t been specifically studied, Fauci said.
“We do not know, but in experience from other infections, if you’re infected, there’s probably a few months’ grace period where you really have enough ongoing immunity that you’re not going to get reinfected,” he said. “For the most part, you likely will have a few months’ period of protection. But after that, we are seeing that it does wane.”
That doesn’t mean reinfection in a shorter time period is impossible, however.
“Anecdotally, you’ll hear a case of someone who got infected and then four weeks later they got infected again — that happens," Fauci said.
A study out of Qatar — which hasn’t yet been published in a peer-reviewed journal — found that an omicron infection within the previous six months was 80% effective against reinfection with the BA.4 or BA.5 subvariants. Previous infections with earlier variants, however, were much less effective against BA.4 and BA.5, at just 28%.
If I'm reinfected, will the symptoms be milder or worse?
For the most part, reinfections are likely to be less severe than previous infections, thanks to higher levels of immunity.
Another study out of Qatar of nearly 1 million people found that a previous infection was 97% protective against severe disease from any variant — in other words, reinfections didn’t result in more severe illness. The study was posted to a pre-print server and hasn’t yet been published in a peer-reviewed journal.
“Normally, the reinfections are milder,” Iwasaki said. “It’s less likely that you get sicker the second time.”
She added that people may have been vaccinated and boosted since their first infections, conferring higher levels of immunity to begin with. “And those types of infections tend to be milder.”
Whether you have gotten a mild infection or severe infection, there’s no guarantee for preventing future infection.
Akiko Iwasaki, Yale University
Fauci said that “prior infection and the immunity induced by prior infection, as well as the vaccination-induced immunity, continues to do quite well in protecting against severe disease.”
Still, some people may get sicker when they are reinfected, for example if someone is exposed to a much higher amount of virus than in the first infection or if a person’s immunity against Covid has waned significantly, Iwasaki said.
Elderly people with underlying conditions or immunocompromised people, while vaccinated, may not be as protected against severe disease, even after previous infections, Fauci said.
Are certain people more vulnerable to reinfection?
Public Health England, the British equivalent to the U.S. Centers for Disease Control and Prevention, regularly tracks reinfections.
According to its most recent analysis, from mid-May, people who were unvaccinated or younger or had mild or asymptomatic infections with lower viral loads were more likely to be reinfected.
Iwasaki said those who have more severe infections tend to develop more robust immune responses to the virus. Even so, the immune response will wane over time.
“Whether you have gotten a mild infection or severe infection, there’s no guarantee for preventing future infection,” she said.
Am I more likely to develop long Covid if I get reinfected?
There’s no evidence that a repeat infection is more likely to lead to long Covid, or lingering symptoms, after an infection, Fauci said.
Iwasaki agreed, adding that while it’s unlikely that multiple infections could increase risk for long Covid, scientists just don’t know yet.
“Immunologically, it’s unlikely that you’re going to develop long Covid after a second or third infection, because you’ve already developed some levels of immune responses,” Iwasaki said.
But, she added, she wouldn’t make any bets on that.
“That data’s just not available right now.”
Follow NBC HEALTH on Twitter & Facebook.
