A Brief Guide On Mixing And Matching COVID Booster Shots

You don't have to get the same vaccine you got the first time around. But should you? Here's what experts personally recommend.
Here's how to weigh which COVID vaccine booster to get.
Yulia Naumenko via Getty Images
Here's how to weigh which COVID vaccine booster to get.

Millions of American adults are now eligible for COVID booster shots and health officials have approved a mix-and-match approach. But they’ve declined to make specific recommendations beyond that, so it’s very much so a choose-your-own adventure situation.

Should you stick with what you got the first time around? And if you change it up, what’s your best bet? HuffPost spoke with several experts about how to choose the best booster for you.

Who is eligible?

Per the Centers for Disease Control and Prevention and Food and Drug Administration, you’re currently eligible if you received either the Pfizer or Moderna mRNA vaccines and you’re 65 and up, or if you’re 18 older and you live in a long-term care setting, have certain underlying health conditions or work in a high-risk job. It must be at least six months since you got your second dose.

You’re also eligible for a booster if you received the Johnson & Johnson vaccine and you’re 18 or older and it’s been two months since your first shot.

Why did health officials approve mix-and-match shots?

For one, convenience. For example, if the pharmacy down the road only offers Moderna and you initially got Pfizer, you no longer need to find somewhere else to go. Experts have long known that convenience is a key element of getting people to roll up their sleeves.

But it’s not just about access. Emerging evidence also suggests mixing-and-matching vaccines may produce a slightly stronger antibody response.

What should I do if I got the Johnson & Johnson vaccine?

First and foremost, get a booster. The original shots are still effective at preventing hospitalization and death, but people at greater risk for severe COVID — aka those who are eligible for the booster — should roll up their sleeves to increase their immunity. Real-world data collected between last March and August suggests that one Johnson & Johnson shot is about 71% effective at preventing hospitalization among otherwise healthy adults, whereas two shots of Moderna are about 93% effective and Pfizer is 88% effective.

Several experts told HuffPost their preference would be for people to get boosted with an mRNA vaccine. Preliminary reports show people who got Johnson & Johnson had higher antibody levels if they were boosted with one of the two mRNA vaccines than if they were boosted with another Johnson & Johnson shot. Combining vaccines seems to jolt the immune system into producing a more robust response.

“I think my colleagues and I would be harmonizing on the same song here: mainly, that you get bigger antibody responses if you get a boost with an mRNA vaccine, either Pfizer or Moderna,” William Schaffner, an infectious disease specialist with Vanderbilt University Medical Center, told HuffPost.

“If individuals asked me, I would say, ‘Oh yeah. Go get yourself a Pfizer or Moderna,’” Schaffner said.

That said, you can absolutely stick with Johnson & Johnson. The company has said that a booster dose of its vaccine provides 94% protection against moderate to severe COVID — and can increase initial antibody levels by four to six times. Health officials did raise some questions about the strength of that data, but ultimately gave the green light to the Johnson & Johnson booster.

And antibodies are not everything. Vaccines also ignite other key parts of the immune system, like T-cells, which help fight infection and that are much more difficult to measure.

What should I do if I got one of the mRNA vaccines?

Technically, you can get any of the three vaccines, but experts say that either of the mRNA vaccines is your best choice.

Some early evidence suggests Moderna creates a slightly stronger immune response and may hold up a bit more over time — and preliminary reports that say people who get Moderna and are boosted with Moderna have the strongest immune response. But that evidence is still new. And it’s important to keep in mind that the Moderna booster is smaller than the initial two shots.

“It goes from 100 micrograms to 50 micrograms for the booster dose. There are some data out there that suggest the Moderna vaccine does produce higher levels of antibody when compared head to head with the Pfizer vaccine, but all of those data are with that 100-microgram dose,” explained Colleen Kelley, an associate professor in the division of infectious diseases with Emory University School of Medicine.

Ultimately, it’s up to you. Some people might take a grass-is-greener-on the other side approach and try a different mRNA vaccine than they initially received; others might want to stick with what they know. Experts say both approaches are reasonable, and both approaches work.

“As far as mixing and matching, are you going to achieve any noticeable benefit as far as protection if you had Pfizer and switched to Moderna or vice versa? I don’t think we can say at this point in time — except that they’re both fantastic vaccines,” Kelley said.

Still have questions or are unsure what to do?

Talk to your doctor. They can talk you through your health background and any considerations for you to have in mind.

“We know the J&J vaccine have a risk of thrombosis with thrombocytopenia (TTS), so for younger women we’d probably counsel them about that particular risk. For people who had an allergic reaction with the mRNA vaccine, they might be someone who could try a J&J vaccine,” said Inessa Gendlina, director of infectious diseases at Montefiore Health System. There’s also a slightly increased risk of developing myocarditis after the two mRNA vaccines, particularly in young men, she pointed out — but ultimately all of these risks are very rare.

Still, if you’re really tossing and turning over which shot to get, these are the types of factors your doctor might take into consideration. “It’s a discussion about personal risk, personal history,” Gendlina said.

As ever with COVID, things change as new data emerges. For some time before the new mix-and-match recommendations came out, health officials really tried to dissuade people from trying something else — which might add another layer of confusion for some people. But it’s not a flip-flop. Medical advice often pivots based on new research, and health officials were being particularly cautious early on.

“We’re learning more as we go along. In the beginning, these were brand new vaccines and we wanted to give these vaccines exactly by the book because we didn’t have data,” Schaffner said. “Now we’ve accumulated data that mixing and matching not only is safe, but might actually give you more of a boost.”

As you make booster decisions, keep in mind the bottom line: all three COVID vaccines are continuing to do an excellent job of keeping people out of the hospital. And getting that additional dose if you qualify will only help you avoid getting seriously sick as we head into the colder months.

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.