For many of those who have tested positive for COVID-19 this summer, this isn't their first rodeo.
This article first appeared in Salon.
In California, new data released by state officials showed that one out of every seven new cases in July was a reinfection. New York health officials have recorded 328,100 cumulative reinfections and 5.77 million infections — suggesting about 5.6 percent of cases are second-time infections. (Reinfections are not tracked at the federal level.)
Unlike summer 2020 — when researchers believed that it was unlikely someone could get the coronavirus twice — so-called re-infections are considered to be the "new normal." New subvariants of omicron are considered particularly adept at re-infecting those who've had previous infections.
But just how many times can a person get COVID-19? Particularly among those who have already had COVID at least once, knowing the answer to that question could affect their personal calculus of risk aversion.
The answer is not hopeful.
"I would say there's no limit, unfortunately," Dr. Monica Gandhi, infectious disease doctor and professor of medicine at the University of California–San Francisco, told Salon. "I hope it is obvious to people that we can't eradicate it by now."
Gandhi noted that there are less dangerous coronaviruses that cause the common cold, and noted that those cold-causing coronaviruses frequently reinfect. Indeed, it is estimated that the average person will have 200 colds in their lifetime (although not all are caused by coronaviruses).
Deepta Bhattacharya, associate professor of immunobiology at the University of Arizona who previously co-authored a paper in 2020 that suggested that immunity to COVID-19 lasts "at least several months after SARS-CoV-2 infection," told Salon the answer to how many times a person can get reinfected will depend on how the virus keeps mutating.
"It really depends on how much the virus changes and how long it takes for it to change from whatever it was that you were infected with, or got vaccinated against, in the first place," Bhattacharya told Salon.
Bhattacharya said what makes the mutations difficult to predict and control is that they are likely happening in multiple ways. While viruses are technically not alive, it is their nature to mutate and evolve as they infect hosts' cells and replicate; this is how they survive. But some researchers have theorized that the coronavirus has also been mutating repeatedly inside people with compromised immune systems who can't clear the virus for an extended period of time. This scenario is what some suspect happened with the omicron variant, which had surprising mutations. Indeed, omicron's mutations have a remarkable ability to evade immunity from vaccines, previous infection, or both.
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As Bhattacharya explained, omicron and its subvariants' mutations led us to the current situation, where reinfections are a constant threat.
"The key thing that has changed — it's not so much that the immune response is fading out so quickly, it is that the virus is mutating to escape from it," Bhattacharya said. "And that's really the major driver of reinfections."
If the virus had stayed the same and not mutated, Bhattacharya said, he doesn't think we'd be dealing with infections right now. With BA.5 the new dominant strain in the U.S., researchers are even more positive that re-infections with this subvariant are likely, even if you've been infected with (previous omicron subvariant) BA.1, as noted by a study published in the journal Cell.
According to the Centers for Disease Control and Prevention (CDC), studies suggest that reinfection with the same virus variant as the first infection — or, reinfection with a different variant — are both possible. Shockingly, reinfection can happen within a mere 90 days of the initial infection. A specific report that identified 10 people who got reinfected found that they occurred between 23 to 87 days after initial infection.
"If you did recover from a prior infection, even if it was the original strain, and then you got hit with omicron, there is still some protection — and your odds of getting really sick and landing in the hospital are still lower," Bhattacharya noted.
Bhattacharya told Salon he is unsure if reinfections occurring within such a short period of time after the initial COVID-19 are "the rule or the exception." Even though reinfections are likely as the virus mutates to evade immunity, that doesn't mean that you aren't building immunity through infection or vaccination.
"If you caught delta towards the end of its wave in October you could totally get infected again in January by omicron because omicron is really different from delta," Bhattacharya said. "You can see cases like that for sure. But would you get infected by delta twice within three months? That's not very likely."
Bhattacharya emphasized that if a person is infected with one strain, they will at least have some immunity to protect them from the next.
"If you did recover from a prior infection, even if it was the original strain, and then you got hit with omicron, there is still some protection — and your odds of getting really sick and landing in the hospital are still lower," Bhattacharya noted. "When you do get infected, and I think the data is pretty clear, on average, they tend to be not as bad."
Gandhi added that T cells and B cells from previous infections (or vaccinations) will prevent you from having severe disease if you are reinfected. The immune system produces both B and T cells in response to an infection; B cells produce antibodies and T cells specifically attack and kill pathogens. Following vaccinations for other infections, like measles, mumps, rubella, pertussis, and diphtheria, T cell immunity is long lasting. Research has shown that T cells can protect against COVID-19 even if antibodies wane.
"The easiest way to think about it is that mild infections are prevented by antibodies, and T and B cells are basically protecting us against severe disease," Gandhi said. SARS-CoV-2 antibodies are believed to decrease over time.
However, this is not to say there aren't any risks to getting reinfected with COVID-19. One study published in July suggested that having repeated COVID-19 infections appears to increase the chances of a person having long COVID.
As far as the effect on the immune system, Bhattacharya debunked misinformation that has surfaced suggesting reinfections take a severe toll on a person's immune system.
"It is highly unpleasant to get infected over and over again, and so to the extent you are able to prevent that from happening, I would recommend it for sure," Bhattacharya said. "The immune system is pretty resilient."
Bhattacharya said that with the help of variant-targeted vaccines, we may be approaching a future where reinfections are no longer as common.
"I do think we can eventually get to the point where we're not worrying about getting infected every few months," he said.