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Already Had COVID? Here's How Long You May be Immune

Reinfections are common.
FACT CHECKED BY Emilia Paluszek

If you've had COVID-19, chances are you're not eager to repeat the experience. Unfortunately, the virus has evolved in such a way that reinfections are common. If having the virus once doesn't protect you from getting it again, the question becomes: How long does your immunity last? Here's what the experts say. Read on to find out more—and to ensure your health and the health of others, don't miss these Sure Signs You've Already Had COVID.


Omicron Created a Blurry Immunity Picture

man sick wearing mask at home, monkeypox self-isolation

Earlier in the pandemic, studies found that contracting Delta or an earlier variant was 84 to 90 percent effective in preventing reinfection. 

Then came Omicron. Initial studies found that Omicron only provided about 50 percent protection against reinfection. And it has evolved into subvariants—BA.4 and BA.5—that are not only more contagious than their already highly contagious predecessors, they're more likely to cause reinfections. That's because they're able to overcome immunity caused by vaccination or a previous infection. 


Could Immunity Last Only Weeks?

Young sick woman laying in her bed.

Earlier in the pandemic, experts thought being infected with Omicron might protect you from another bout with the virus for at least three months. The virus has evolved to narrow that window—to as little as 20 days, according to a pre-print study by Danish scientists, who found that some people have been reinfected with another Omicron subvariant around that time.


A Range of Potential Immunity

Sick woman holding her throat.

So what's the bottom line? What length of immunity can you expect? As with so many things about the pandemic, the answers are unclear and a range of scenarios are possible. 

"It isn't yet possible to calculate this figure with any accuracy, although we can get a hint from existing data," New Scientist reported last month. In the UK, the Office of National Statistics analyzed reinfections there from the start of the pandemic to mid-December 2021, when Omicron had been the dominant strain for several weeks. They found the time between reinfections ranged from 90 to 650 days, with the average being 343 days—almost a year. Of course, those statistics only accounted for a few weeks of Omicron (BA.2), and we're now on BA.4 and BA.5. 


Reinfections Seem Milder

woman coughing into elbow while lying down on sofa in the living room.

What is clear, experts say, is that reinfections seem to be shorter and milder so far. That's because the immune system, having encountered the virus before, remembers how to react to it, shortening illness if not preventing reinfection. And being fully vaccinated and boosted continues to provide robust protection against serious illness, hospitalization or death.

"I've thought, almost since the beginning of this pandemic, that COVID-19 is eventually going to become an inevitable infection that everybody gets multiple times, because that's just how a new respiratory virus gets established in the human population," Dr. Amesh Adalja, an infectious-disease specialist at Johns Hopkins University, told the New York Times last week.

"It's a really frustrating situation, because I think everyone wants to be done with this virus, but we're just not. And we live in an era where we just want complete information at our fingertips, but we don't have it," Jacob Lemieux, an infectious disease doctor at Massachusetts General Hospital, told NPR

That means it's important to stay informed about the latest public-health recommendations about the virus, including masking and social distancing when advised.


How to Stay Safe Out There


Follow the fundamentals and help end this pandemic, no matter where you live—get vaccinated ASAP; if you live in an area with low vaccination rates, wear an N95 face mask, don't travel, social distance, avoid large crowds, don't go indoors with people you're not sheltering with (especially in bars), practice good hand hygiene, and to protect your life and the lives of others, don't visit any of these 35 Places You're Most Likely to Catch COVID.

Michael Martin
Michael Martin is a New York City-based writer and editor. Read more about Michael