Last year, it seemed that reinfections with the coronavirus were rare. Yes, they happened, but the vast majority of people who had already had COVID probably wouldn’t catch the virus again anytime soon.
But recent data suggests reinfections are becoming more common, especially as new variants emerge. The New York Department of Health recently published a report showing that just over 4% of all COVID infections in the state are reinfections — and nearly 87% of those have occurred since December 2021. Washington State reported that 45,312 people had reported reinfection since September 2021 – 2.3% of those were hospitalized and 0.2% died.
The increase in reinfections is likely influenced by two factors: one, that newer variants can evade and re-infect the antibody response, and two, that we are now more rigorously documenting reinfections and getting a more accurate picture of how common they are.
Coronaviruses are known to infect people over and over again. In fact, it is widely believed that the common cold coronaviruses circulating (and often re-infecting people) today come from past coronavirus epidemics. Many infectious disease doctors suspect that, as with those strains, we are susceptible to reinfections, but that the symptoms will get milder and milder over time.
“As we gain immunity, as our T cells diversify and broaden, hopefully our second reinfection won’t feel as bad as the first infection,” said Monica Gandhian infectious disease specialist at the University of California, San Francisco.
Here’s how quickly reinfections can now occur with COVID.
We now know that antibodies, which primarily work to prevent infection, are starting to decline a few months after vaccination or infection. In addition, as the coronavirus mutated, it became a little less recognizable to the immune system.
This allows variants to outwit the immune system’s first line of defense and reinfect us, according to Julie Parsonnetan epidemiologist and professor of infectious diseases at Stanford University School of Medicine.
“With omicron, we see a lot of cases in previously infected people, even if they were also vaccinated,” Parsonnet said.
“With omicron, we see a lot of cases in previously infected people, even if they were also vaccinated.”
– Julie Parsonnet, epidemiologist and professor of infectious diseases
Pablo Penaloza-MacMasteran assistant professor of microbiology immunology at Northwestern University Feinberg School of Medicine, said people who have recently recovered from infection or received a boost may be susceptible to reinfection within about six months.
Parsonnet noted that she had heard of at least one patient who had been fully vaccinated and double-shot had been infected with omicron six weeks after their previous infection.
A recent study from Denmark, however, thought so all in rare cases, 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 does not mean that there is a good chance of getting COVID again a few months after recovery. In fact, a preprinted 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 you antibody levels† and that should protect most people well from infection for at least four months, Gandhi said.
Identifying who is more likely to get reinfected isn’t an exact science – some people will be better protected and less at risk of re-infection, depending on factors such as their age, genetics and underlying health. The rate of reinfection also depends on the variant — the type of mutations the virus picked up — and the viral load a person is exposed to, according to Penaloza-MacMaster.
Reinfection is usually less severe.
Most of the evidence suggests that COVID reinfections are generally less severe than the initial infection. in Danish studyalmost everyone who was re-infected with BA.2 after having previously had BA.1 had mild symptoms for a few days and a significantly lower viral load the second time – even those who had not been vaccinated.
Even though our immune system weakens over time, the components that hold us down safe from disease and severe outcomes remain robust and long-lasting (even when handle new variants†
†Reinfections, especially in vaccinated individuals, tend to be milder than the primary infection because there is already an arsenal of memory T cells and B cells,” according to Penaloza-MacMaster.
Research suggests that reinfections and boosters amplify the T-cell response. “As you might expect, reinfection fundamentally protects you even more” from serious consequences, Gandhi said. Boosters are the safest, of course – you don’t want to deliberately get infected again.
According to Penaloza-MacMaster, the severity of a person’s reinfection is also affected 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 affect long-term COVID?
One of the key questions epidemiologists will follow is how reinfections contribute to long-term COVID.
We know that COVID affects many organs, including the brain, lungs and heart. Inflammation, which helps to clear infected cells from the body, is a normal part of the body’s response to infection. When the body kills virally infected cells, it also destroys our own healthy cells.
“Econtainment of a virus involves a significant amount of ‘collateral damage,’ which is a major reason why prolonged inflammation — which occurs during long-term infections — is harmful,” Penaloza-MacMaster said.
if and hhow reinfections contribute to long-term COVID and possible damage to our organs is unclear. Research has found that vaccination reduced the risk of long-term COVID-19 in people with breakthrough infection, Gandhi said. And while the vast majority of people who contract SARS-CoV-2 make a good recovery with no long-term consequences, it is not yet known whether this will continue after multiple infections.
“We don’t know the answer to this question, mainly because as variants change and our immune system responds differently to them, their effects on the body change a lot,” Parsonnet said.
Experts are still learning about COVID-19. The information in this story is what was known or available at the time of publication, but guidelines may change as scientists discover more about the virus. Consult the Centers for Disease Control and Prevention for the latest recommendations.
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