What Happens If You Get COVID-19 In Between Vaccine Doses?

Here's what to do if you test positive for the coronavirus before your second Pfizer or Moderna shot.
Capuski via Getty Images

Millions of Americans are being vaccinated with the two-dose mRNA COVID-19 vaccines from Pfizer and Moderna, and both options are remarkably effective at protecting against the coronavirus. But getting protection from the shots takes time.

If you receive the Pfizer vaccine, you’ll need to wait three weeks in between your first dose and your second dose, or as close to that interval as possible. If you receive the Moderna vaccine, you’ll wait four weeks in between shots. (And for both, you’re not considered fully vaccinated until two weeks have passed after your second dose.)

So what happens in between? Can you become infected with COVID-19? And what do you do about it? Here’s what you need to know.

Yes, it is definitely possible to get COVID-19 after your first shot.

You might feel elated after you get your first dose of the Pfizer and Moderna vaccines, and understandably so. The vaccines are being hailed as miraculous because of how quickly they were developed, as well as because of how effective they are.

But it takes time for your immune system to start to build up a response, and experts still aren’t entirely clear exactly how much protection people have after just one shot. Current studies suggest that a single dose of the Pfizer or Moderna vaccine is about 80% effective in preventing COVID-19 infection about two weeks after your first shot.

“It definitely can and does happen,” said Paul Pottinger, an infectious diseases expert at the University of Washington, referring to the possibility of getting infected between two doses. “Remember, we even see COVID-19 infections in patients who’ve been fully immunized, meaning a solid two to five weeks after their second dose of either of or mRNA immunizations.”

Researchers have known about this possibility since the get-go. Pottinger pointed out that the original clinical trials for the Pfizer and Moderna vaccines showed they were both roughly 95% effective in preventing COVID-19 after both shots. But some of the vaccine recipients who ended up getting sick during the trials were in between their two doses.

“What I would say is, if people are worried about catching COVID-19 in the middle of their immunization process, damn right,” Pottinger added. “They should be worried about this, because they’re not yet protected.”

But you should be really well protected against severe illness and death.

Researchers and health care providers are basically allergic to absolute terms when it comes to talking about anything to do with human health and medicine, so you’ll really never hear one say something is 100%. But one shot of the mRNA vaccines seems to come pretty darn close to perfection in terms of preventing hospitalization and death.

“People who have received their first dose are dramatically well protected against hospitalization or death,” Pottinger said.

“In the studies, nobody who got vaccinated died. Obviously in the real world, we have many, many more people, but they’re still extremely, extremely effective at preventing severe disease and death,” added Valerie Cluzet, an infectious disease physician and medical director of infection control and antibiotic stewardship at Nuvance Health.

“That’s true certainly after your second dose, but probably also true for after the first dose,” she noted.

If you get COVID-19 between doses, you should still get your second dose — but the timeline will likely be different.

No matter what, you should still plan to get your second shot. That’s because, as the Centers for Disease Control and Prevention explains, experts still don’t really know how long people are protected from getting sick again after recovering from COVID-19 — and reinfection is possible.

However, experts do know a bit more about how long vaccines protect you. Current evidence suggests people who receive the Pfizer or Moderna vaccines have robust protection for at least six months (and counting).

That said, if you do get COVID-19 in between doses, the timing of your second shot might change a bit. For one, you should not plan to get vaccinated until you’ve met the criteria set forth by the CDC to end your isolation. That’s partly to keep others safe while you should be in quarantine. But it’s also to give your body the best shot at developing a robust immune response.

“You should be waiting until you’re over the acute illness. You really want to give your immune system the best chance possible to respond to the vaccine,” Cluzet said.

Also, you might opt to temporarily delay vaccination while supplies remain really in demand.

CDC has said that as long as you’re cleared to leave home you can be immunized on schedule, or as close to on-schedule as you can, but because this is such a precious resource, the CDC has asked us to consider delaying the second dose by 30 days from the onset of symptoms, because that allows other people to get immunized ... it’s a courtesy to our fellow citizens,” Pottinger explained.

It’s important to continue masking up and maintaining social distance.

Again, even after you’ve been fully immunized, “vaccine breakthroughs” are expected. That is one reason why some recommendations for fully vaccinated individuals have changed (like being able to congregate with other vaccinated people sans masks), while others have not budged.

It’s still important for everyone to mask up and maintain social distance. If you’re vaccinated, you should still be doing these things unless you’re in a private place with other vaccinated individuals or one other low-risk, unvaccinated household. If you’re not yet vaccinated, get whatever vaccine is available to you, whenever it’s available to you.

“We’re learning more and more that the vaccines also are preventing transmission, so not only are you protecting yourself, but you’re protecting others,” Cluzet said. “It’s personal health, but it’s also public health.”

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