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Can someone who has recovered from COVID-19 still spread it to others?

MIT Medical answers your COVID-19 questions. Got a question about COVID-19? Send it to us at CovidQ@mit.edu, and we’ll do our best to provide an answer.

My daughter’s family and my sister-in-law’s family have all survived the COVID-19 virus. They want to include my husband and me in a holiday gathering. My daughter says this is safe for us, because everyone else who will be there is immune. But what if one of them was exposed to an infected person before our get-together? Could they somehow carry the virus to us and make us sick?

view of hands presenting a gift decorated with COVID-19 molecules with a tag reading 'to Grandma'

We’ve been getting questions like this more and more often recently. The short answer is that people who have recovered from COVID-19 cannot spread the virus to others unless they become reinfected themselves. The bad news is that reinfection is possible.

From what we know of other viruses, most experts think it’s likely that most people who recover from COVID-19 have some level of immunity for some period of time. But we don’t know how much immunity they have or how long it lasts. A recent study of a different type of coronavirus, the common cold, found that people were often reinfected within 12 months.

When we first wrote about the possibility of COVID-19 reinfections two months ago, we reported four confirmed cases. Today, we know of at least 30, but this is almost certainly an underestimate. This is because a confirmed case of reinfection requires genetic proof that the virus was sufficiently different the second time. Genomic sequencing of this type requires viral samples from both PCR tests; it also requires time, money, and other resources that are often in short supply. As a result, the number of confirmed reinfections is far lower than the more than 2,000 suspected cases that have been reported to date.

And it’s likely that many other instances of possible reinfection go unreported or, worse, undetected. Immunologists usually expect a second infection with the same virus to be milder than the first. If that holds true for most reinfections with the SARS-CoV-2 virus, many reinfected individuals could remain asymptomatic and untested but very much capable of transmitting the virus to others.

Unfortunately, this means that your relatives’ previous COVID-19 infections do not make them safe holiday companions for you, or even for each other. Nor does pre-holiday testing guarantee a safe gathering.

This holiday season, there’s no safe way to get together with people outside of your own household or bubble. But while it can feel like we’re all stuck in a never-ending marshmallow experiment, vaccines offer light at the end of this very long tunnel. Postponing extended-family gatherings now makes it more likely that we’ll be able to gather for holiday celebrations next year — and for many years to come.

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