The First Big Study On COVID-19 Reinfection Is Here. Here's What It Means.

Can you get the coronavirus twice? How long do you have immunity? This new report provides a lot of insight.
A large new study shows what we can expect with COVID-19 and reinfection.
Luis Alvarez via Getty Images
A large new study shows what we can expect with COVID-19 and reinfection.

The possibility of coronavirus reinfection has been a concern since the first reports of people getting sick again began popping up in 2020 ― while many around the globe were still in isolation. But there has been relatively little data up until this point on how widespread a phenomenon this is.

The first large-scale investigation to tackle that question was published in The Lancet this week, and it found that the vast majority of people who have had COVID-19 are indeed protected from catching it again — for at least six months. However, people ages 65 and older are far more likely than younger individuals to experience repeat infection.

The researchers analyzed data from Denmark’s national COVID-19 testing program, which has offered free PCR testing to roughly 4 million people living in the country. Overall, they found that a very small percentage of the population — 0.65% — experienced reinfection.

For those 65 and under, getting the coronavirus once provided roughly 80% protection against reinfection. But for people 65 and older, it provided only about 47% protection against getting COVID-19 again, further highlighting how dangerous this disease can be for older adults.

“Since older people are also more likely to experience severe disease symptoms and, sadly, die, our findings make clear how important it is to implement policies to protect the elderly during the pandemic,” Steen Ethelberg, the study’s author from the Statens Serum Institut in Denmark, said in a statement. “Given what is at stake, the results emphasize how important it is that people adhere to measures implemented to keep themselves and others safe — even if they have already had COVID-19.”

“Given what is at stake, the results emphasize how important it is that people adhere to measures implemented to keep themselves and others safe.”

- Steen Ethelberg, researcher at Statens Serum Institut in Denmark

What this study means for us (and the future of the pandemic)

Overall this news is positive, but it also highlights the need for continued vigilance. Many factors could still play a potential role in getting sick.

The emergence of different variants is one of them. Coronavirus reinfection has become a particular concern over the last few months as new variants have begun circulating around the globe.

A vaccine study in South Africa — where a variant is circulating that experts fear is more contagious and may make the current vaccines less effective — found new infections in 2% of people who’d previously been infected with a different variant of the coronavirus.

The large new study out of Denmark did not examine the role of variants in reinfection, given the time frame of the research. So it does not offer any clues about whether variants make it more likely for someone to come down with COVID-19 more than once.

Previous case studies of people who have been reinfected were troubling because they suggested it was possible to become sicker the second time. This was the case with an otherwise healthy 25-year-old man in Nevada who tested positive for COVID-19 last spring, recovered, then fell ill with it again. He required hospitalization the second time. But even as those first reports emerged and attracted significant news coverage, researchers were careful to point out the rarity of that outcome.

Since the new study on reinfection was not conducted in the United States, it’s unclear whether the findings apply in the same way here. But on the whole, researchers are optimistic that most people who get COVID-19 will not experience reinfection soon after. And they are continuing to study immunity, both after infection and after vaccination. It’s unclear at this point how long immunity lasts after a person receives a COVID-19 vaccine.

All of this underscores the continuous need for basic preventive measures, even as coronavirus cases are starting to fall nationwide.

The Centers for Disease Control and Prevention recommends that people who have had COVID-19 should get vaccinated once it’s available to them, in large part because there is a slim chance they could become infected again if they come into contact with the virus.

Continued mask-wearing is also essential, as questions remain over the extent to which those who have recovered from COVID-19 are able to spread it to others if they’re exposed again. Additionally, mask-wearing helps decrease the small chance of an individual getting the virus more than once.

Earlier this month, the CDC released new guidelines saying that fully vaccinated Americans can safely gather indoors without wearing masks or social distancing, providing a promising glimpse at how restrictions will likely loosen as more shots go into more arms. But for now, it is a race against the clock to ensure millions of Americans are immunized as variants continue to spread.

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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