In 2020, Covid reinfections were considered rare.
In 2021, breakthrough infections in vaccinated people could occur, but again the risk was low.
In 2022, this is no longer the case either. As more immune-evading coronavirus variants emerge, reinfections and breakthrough infections seem increasingly normal.
The United States does not currently track Covid reinfections. However, researchers in the UK have found that the risk of re-infection was eight times higher during the omicron wave than it was during the delta wave last year.
“I wouldn’t be surprised if we saw people getting infected more than once a year,” Dr. Anthony Fauci, President Joe Biden’s chief medical adviser, said in an interview with NBC News last week, though he added that he felt optimistic that it will eventually settle down to become just a seasonal occurrence, like the flu. (Fauci, who received two booster shots, himself tested positive for Covid on Wednesday, saying he had mild symptoms.)
Of course, just because reinfections are possible doesn’t mean people should give up all efforts to prevent them; staying up to date on vaccinations and wearing masks indoors in places with high transmission always work to reduce risk.
Here’s what we know so far about reinfections.
Can I be re-infected if I have already had Covid, or been vaccinated or boosted?
To put it bluntly, yes. Experts agree that reinfections are possible, even in people already infected or those who are up to date on their vaccines.
“Reinfections, unfortunately, are not unusual for coronaviruses,” said Akiko Iwasaki, a professor of immunobiology at Yale University. “That’s just the nature of this viral infection.”
The coronavirus that causes Covid isn’t unique — other types of coronaviruses that cause colds can also reinfect each other, Fauci said. But these reinfections can happen every two or three years because these viruses don’t change much.
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This is not the case for SARS-CoV-2, and in particular the rapidly evolving omicron subvariants, which are effective in 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.”
This is 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 – which are now taking hold in the US – are quite different from BA.1, so “it’s not a guarantee” that having a past omicron infection will protect you later subvariants, she said.
How many times can I be re-infected?
It is impossible to quantify exactly how many times a person can be re-infected, experts say.
With a high level of Covid currently spreading in the United States, each of us has a good chance of being exposed to someone who is contagious – and of being re-infected.
Whether a person is reinfected depends on the strength of the immune response at the time the person was exposed, as well as whether they were recently vaccinated, said Dr Julie McElrath, director of the vaccines division and infectious diseases at the Fred Hutchinson Cancer Center in Seattle. Multiple exposures to the virus — which don’t necessarily lead to symptoms — could have a silver lining, McElrath said.
Each time a person is exposed, the immune response matures and improves.
“We should see reinfection as part of the new normal,” she said. “The hope is that with these multiple exposures, continued improvement in antibody response will occur.”
How long does Covid immunity last after infection?
Whether a person is less likely to be reinfected in the weeks following an infection has not been specifically studied, Fauci said.
“We don’t know, but from experience with other infections, if you’re infected, there’s probably a grace period of a few months where you really have enough continuous immunity to not get re-infected,” he said. “For the most part, you’ll probably have a protection period of a few months. But after that, we’re seeing it go down.
This does not mean, however, that reinfection within a shorter period of time is impossible.
“Anecdotally, you’ll hear the case of someone who got infected, then four weeks later they got infected again — it happens,” Fauci said.
If re-infected, 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.
“Normally, reinfections are milder,” Iwasaki said. “You are less likely to get sicker the second time around.”
She added that a person may have been vaccinated and boosted since their first infection, conferring higher levels of immunity to begin with. “And those types of infections tend to be milder.”
Whether you contracted a mild or severe infection, there is no guarantee of preventing future infection.
Akiko Iwasaki, Yale University
Fauci noted that “prior infection and immunity induced by prior infection, as well as immunity induced by vaccination, continue to protect well against serious disease.”
Still, some people can get sicker when reinfected; for example, if someone is exposed to a much higher amount of virus than the first infection, or if a person’s immunity to Covid has dropped significantly, Iwasaki said.
Older people with underlying conditions or immunocompromised people, although vaccinated, may not be as protected against serious illness even after previous infection, Fauci said.
Are some people more vulnerable to reinfection?
Public Health England, the UK equivalent of the US Centers for Disease Control and Prevention, regularly tracks reinfections.
According to PHE’s most recent analysis, from mid-May, people who were unvaccinated, younger, or had mild or asymptomatic infection with a lower viral load were more likely to be re-infected.
Iwasaki said those with more severe infections tend to mount a more robust immune response to the virus. Even so, this immune response will diminish over time.
“Whether you have contracted a mild or severe infection, there is no guarantee of preventing future infection,” she said.
Am I more likely to develop long Covid if I get re-infected?
For now, there is no evidence that repeated infection is more likely to lead to long Covid or persistent symptoms after infection, Fauci said.
Iwasaki agreed, adding that while multiple infections are unlikely to increase long-term Covid risk, scientists simply don’t know yet.
“Immunologically, you are unlikely to develop long Covid after a second or third infection because you have already developed certain levels of immune responses,” Iwasaki said.
But, she added, she wouldn’t bet on it.
“That data is simply not available at this time.”
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