How Long After Having Covid Can I Get a Booster Shot?

Millions of people who have recently developed Covid-19 may have some new questions about their immunity. If they have not yet received a booster shot, do they still need to get one? And when is the optimal time to get it?

Federal health officials continue to recommend that everyone get vaccinated and boosted, regardless of whether they’ve had Covid-19 in the past. But more than half of fully vaccinated Americans who are eligible for booster shots have not yet received them. And the guidance on when to schedule a booster appointment after recovering from Covid-19 is less than clear. Here’s what we know.

What’s the point of getting a booster after you’ve had Covid?

Most experts agree that vaccines can offer a more reliable and effective immune boost than a natural infection can.

When you get infected with the coronavirus, your immune system mounts a series of responses that bulk up the body’s defenses against future infections. One of the best ways scientists know how to measure that response is to look at how many antibodies you’ve produced. In general, people who’ve been infected with the coronavirus tend to have lower levels of antibodies than those who’ve been vaccinated, said Aubree Gordon, an epidemiologist at the University of Michigan.

One of the reasons for this difference is that infections trigger many different parts of the immune system, and the size of the antibody response will depend on factors like how much virus you inhaled, whether you have underlying medical conditions and the severity of your symptoms. “You may have a high level if you were sicker or sick for longer,” Dr. Gordon said. “But it’s still going to be lower than what we see with the vaccine.”

Vaccines provide a tailored set of instructions for the immune system to use in the absence of any distractions, such as an active infection, said Paul Thomas, an immunologist at St. Jude Children’s Research Hospital in Memphis. And most people who get vaccinated develop a strong and predictable antibody response. A booster shot reminds the body to bump up its defenses — even faster than the first or second shot — in a matter of days.

Studies also suggest that the antibodies produced after vaccination tend to remain at protective levels for longer.

“I think that’s the biggest argument to get boosted, frankly, even if you’ve had a recent infection,” said Dr. Amy Sherman, an infectious disease physician at Brigham and Women’s Hospital in Boston. “It’s a surefire way to give further protection and make sure your immune system produces peak responses.”

When is the best time to get a booster?

There is no hard and fast rule for when to schedule a booster shot after having Covid-19. The optimal timing will depend on your individual circumstances, including how severe your illness was, how long it’s been since your symptoms resolved and what your risk for re-exposure is.

But if you’re currently dealing with an active infection, the Centers for Disease Control and Prevention recommends waiting at least until you no longer have symptoms and have met their criteria for ending isolation. (Meaning, if you had a mild infection, it’s been at least five days since your symptoms started, your symptoms are improving and you’ve been fever-free for at least 24 hours without the help of medications.)

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That being said, some scientists recommend deferring your booster for even longer. Ali Ellebedy, an immunologist at the Washington University School of Medicine in St. Louis, said that it might make sense to wait until you’ve fully recovered or can get a negative P.C.R. test, though this isn’t a C.D.C. requirement to end isolation and may not occur until a few weeks (or even months) later.

“You just don’t want to overwhelm your system,” Dr. Ellebedy said. Let your immune system rest after fighting off the coronavirus and before asking it to ramp up again with the vaccine. This will also allow for a more refined and durable response, he said.

And for some, Dr. Ellebedy added, there can be a benefit to waiting even longer. If your risk of reinfection is low — for example if you work remotely, are generally healthy and can adhere to public health guidelines for masking and social distancing — it might make sense to wait until your natural immunity is waning, which could occur up to three months after an infection, before getting boosted, he said. Not only will this help to produce a more robust antibody response, but by the time you’re ready to be boosted, there might be a newer version of the vaccine available that will specifically work against Omicron.

“The vaccine is derived from the original strain of the coronavirus, and that doesn’t really exist anymore,” Dr. Ellebedy said. “A few months from now, if an Omicron-based vaccine is available, why not take that to prepare for whatever comes next?” Drug companies have begun testing new versions of the Covid booster, which may be available by the summer.

Of course, deferring a booster isn’t the right option for everyone. If you have a high risk of reinfection or serious illness — whether because of your age, medical conditions, a weakened immune system or because you live or work in a setting that increases your likelihood of exposure — then you may want to boost your immunity with an extra vaccine dose sooner rather than later, Dr. Ellebedy added. Getting your booster sooner may also extend protection to vulnerable family members and children who are too young to receive the vaccine.

And of course, most experts agree that if it’s been more than five or six months since you got Covid-19 and you haven’t been boosted yet, you should do so as soon as you’re eligible.

“The booster provides real material help against preventing you from getting Omicron,” Dr. Thomas said. “And there’s so much Omicron around right now that if you haven’t gotten it already, then this is a chance to avoid getting it.”