Last year, it seemed as though coronavirus reinfections were rare. Yes, they happened, but the vast majority of people who had already had COVID likely wouldn’t contract the virus again anytime soon.
But recent data suggest reinfections are becoming more common, especially as new variants take hold. New York’s health department recently published a report that shows a little over 4% of all COVID infections in the state have been reinfections — and that nearly 87% of them have occurred since December 2021. Washington state reported that 45,312 people had reported a reinfection since September 2021 — 2.3% of those were hospitalized and 0.2% died.
The uptick in reinfections is likely influenced by two factors: one, that newer variants can evade the antibody response and reinfect, and two, that we’re now documenting reinfections more rigorously and getting a more accurate picture of how frequent they are.
Coronaviruses are known to infect people over and over again. In fact, it’s widely believed that the common cold coronaviruses that circulate today (and reinfect people frequently) originated from previous coronavirus epidemics. Many infectious disease doctors suspect that, as with those strains, we may be susceptible to reinfections but that the symptoms will become milder and milder with time.
“As get more immunity, as our T-cells diversity and broaden, hopefully our second reinfection will not feel as bad as the first infection,” said Monica Gandhi, an infectious diseases specialist with the University of California, San Francisco.
Here’s how soon reinfections can occur with COVID now.
We now know that antibodies, which work to prevent infection in the first place, begin to dip a few months after vaccination or infection. In addition, as the coronavirus mutated, it became slightly less recognizable to the immune system.
Because of this, variants are able to outwit the immune system’s first line of defense and reinfect us, according to Julie Parsonnet, an epidemiologist and professor of infectious diseases at Stanford University School of Medicine.
“With omicron, we are seeing many cases in previously infected people, even when they had been vaccinated as well,” Parsonnet said.
“With omicron, we are seeing many cases in previously infected people, even when they had been vaccinated as well.”
– Julie Parsonnet, epidemiologist and professor of infectious diseases
Pablo Penaloza-MacMaster, an assistant professor of microbiology-immunology at Northwestern University Feinberg School of Medicine, said that people who recently recovered from an infection or got boosted may be susceptible to reinfection in about six months.
Parsonnet noted she’s heard of at least one patient who was fully vaccinated and double-boosted getting infected with omicron six weeks after their previous infection.
A recent study from Denmark found that, though very rare, reinfections with omicron subvariants can occur in as little as 20 days. Of the 1.8 million infections recorded between November 2021 and February 2022, 1,739 reinfections were detected within 60 days.
This doesn’t mean that a couple of months after recovering, there’s a good chance you’ll get COVID again. In fact, a pre-print study recently found that infections in people who have already had COVID were 90% less common than in people who had never been infected. Getting infected on top of the vaccine really boosts your antibody levels, and that should keep most people well-protected from infection for at least four months, Gandhi said.
Identifying who may be more likely to get reinfected isn’t an exact science — some people will be better protected and less at risk for reinfections depending on factors like their age, genetics and underlying health. The rate of reinfection also depends on the variant — the type of mutations the virus has picked up — and the viral load someone’s exposed to, according to Penaloza-MacMaster.
Reinfection tends to be less severe.
The bulk of evidence suggests that COVID reinfections, in general, tend to be less severe than the initial infection. In the Danish study, almost everyone who had been reinfected with BA.2 after previously having BA.1 experienced mild symptoms for a few days and significantly lower viral loads the second time around — even those who were unvaccinated.
“Reinfections, especially in vaccinated individuals, are typically milder relative to the primary infection, because there is already an arsenal of memory T-cells and B-cells,” Penaloza-MacMaster said.
Research suggests reinfections and boosters enhance the T-cell response. “As you would expect, a reinfection fundamentally protects you even more” from severe outcomes, Gandhi said. Of course, boosters are the safest ― you don’t want to purposefully get reinfected.
According to Penaloza-MacMaster, the severity of an individual’s reinfection is also influenced by the variant they contract along with the dose of virus they are exposed to and whether they have underlying health conditions that put them at risk. But, often, it can be unpredictable.
How will reinfections impact long COVID?
One of the key questions epidemiologists will track is how reinfections contribute to long COVID.
We know that COVID affects many organs, including the brain, lungs and heart. Inflammation, which helps clear infected cells from the body, is a normal part of the body’s response to infections. When the body kills off virally infected cells, it also destroys our own healthy cells.
“Eliminating a virus involves a substantial amount of ‘collateral damage,’ which is a main reason why long-term inflammation ― which happens during protracted infections ― is harmful,” Penaloza-MacMaster said.
If and how reinfections contribute to long COVID and potential damage to our organs is unclear. Research has found that vaccination reduced the risk of long COVID in people who had a breakthrough infection, Gandhi said. And while the vast majority of people who contract SARS-CoV-2 recover well without long-term consequences, it isn’t yet known whether this will continue to be the case after multiple infections.
“We don’t know the answer to this question, especially because as variants change and our immune systems react differently to them, their impacts on the body many change,” Parsonnet said.
Experts are still learning about COVID-19. The information in this story is what was known or available as of publication, but guidance can change as scientists discover more about the virus. Please check the Centers for Disease Control and Prevention for the most updated recommendations.
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