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Should you mix and match your COVID-19 booster? Experts weigh in

What to know before you mix and match.

When Alex Ossola first got her Johnson & Johnson COVID-19 vaccine earlier this year, she stood in line for three hours outside her local pharmacy. It was "misery," she told TODAY. But at the same time, she was relieved to have the convenient one-dose shot over and done with.

The next week, however, the Food and Drug Administration and Centers for Disease Control and Prevention took the shot off the market briefly due to an emerging link between the vaccine and rare blood clots. And in the following months, breakthrough infections became increasingly common as the data began to show more clearly that the J&J vaccine is less effective at preventing COVID-19 infections and hospitalizations than the Pfizer-BioNTech and Moderna mRNA shots.

More and more it started to feel like "everyone else is getting Gucci and Prada and we're out here shopping at TJ Maxx trying to get some of that," Ossola said. So, when the time came for her booster dose in late October, Ossola knew she wanted one of the mRNA vaccines instead of another dose of J&J. She ended up with Moderna.

"As stuff kept coming out about the Johnson & Johnson vaccine after I got it, I was more and more disappointed that that was the one that I got," Amanda Keller, who also received J&J originally, told TODAY. She, like Ossola, opted for a Moderna booster a few weeks ago.

Now that both the FDA and CDC have signed off on booster doses for just about everyone over the age of 18, this type of mix-and-match strategy is something that a much larger chunk of the public is likely to be considering. But it's not something that everyone should be stressing about, experts told TODAY.

Pretty much all adults should think about getting a booster — of any kind

As of Oct. 21, booster shots were available for people age 65 and older as well as people age 18 and older who have certain underlying health conditions, work or live in high-risk environments, or who live in long-term care facilities. And last week, FDA and CDC advisory panels expanded the eligibility to allow anyone age 18 and older to get a booster dose. People who initially got a Pfizer or Moderna vaccine can get a booster six months after their initial doses, and those who received the J&J shot can get their booster two months later.

"This is what's necessary to get complete immunity. And if you think about it that way, then everyone should get it," Dr. Thaddeus Stappenbeck, chair of the department of inflammation and immunity at the Cleveland Clinic Lerner Research Institute, told TODAY.

Recent research from clinical trials and data from Israel suggests that protection from the vaccines wanes over time. But the data also suggest that a single booster dose can revive that protection. It's not totally clear yet whether or not boosters can help prevent transmission of COVID-19.

But at a time when coronavirus cases and hospitalizations are rising yet again (even among fully vaccinated people), COVID-19 boosters are a welcome idea for many. "If you're considering a booster, just get it," Dr. Gabor Kelen, professor and chair of the department of emergency medicine at Johns Hopkins University, told TODAY. "And if you're not considering a booster, just get it."

Are there any potential benefits to mixing and matching?

For most people, it probably makes the most sense to simply stick with the same manufacturer that you got originally. That's because the best data we have about boosters comes from the drugmakers' clinical trials in which all participants received boosters from the same company as their original doses. "I would just follow the studies," Stappenbeck said. "If you had the Moderna vaccine, I would get the third shot with Moderna. And if you had the Johnson & Johnson, I would get a second shot with Johnson & Johnson because of these well-vetted studies that have been done."

But there is some limited data from smaller studies that suggests some people might get more protection from mixing and matching their booster. One of the most compelling studies of the mix-and-match strategy — also called heterologous vaccination — comes from the National Institutes of Health. In this study, about 450 people who received Pfizer, Moderna and J&J shots originally then received one of the three booster shots. Some people got a booster from the same manufacturer as their initial doses (homologous vaccination) while others got mixed-and-matched boosters.

The results showed that everyone who got any type of booster saw an increase in antibody levels, but for those who got the J&J shot originally there was an extra twist: If they got a Moderna or Pfizer booster, they developed an even greater increase in protective antibodies than with the J&J booster.

"So for that group of people, switching over may actually have an advantage," Dr. Bernard Camins, medical director for infection prevention at the Mount Sinai Health System, told TODAY. (And recent CDC data suggest that more than three-quarters of J&J recipients are doing just that.) But, he continued, the dose of Moderna that was given as a booster in that study was not the same dose as the Moderna booster that's being given out to the public, which is just a half dose. And that may have contributed to the positive Moderna effects in that study.

Studies like this one have another problem, too. "Instead of thousands or tens of thousands of subjects (in the clinical trials), these are hundreds of subjects. So they're really not powered to make adequate conclusions," Stappenbeck explained. "I think they're interesting, but they're not conclusive."

For some people, the potential side effects from the shots may also factor into their booster decision. For example, blood clots appear to be a very rare but serious potential risk from the J&J shot. And those most likely to be effected are women of childbearing age. So if you're in that group, you may want to consider switching over to Pfizer or Moderna, Camins said.

You might not get to choose which vaccine you get

Depending on availability at your local vaccination site, you may not necessarily be able to choose which vaccine you get as a booster. In some cases, the site may require you to stick with the same type of shot that you got for your initial doses. In other cases, you might end up mixing and matching unintentionally.

For Lindsay Mann, who got two doses of Pfizer in the spring, the only option for a booster at her pharmacy was the Moderna shot. "I would have loved to stay in the same, like, vaccine family," she told TODAY, "but I also just wanted to get it." Mann went ahead and received the Moderna booster along with a flu shot and, overall, felt like the experience was "pretty seamless."

A spokesperson for CVS told TODAY that the company does allow people at its pharmacies to mix and match their booster dose, but each CVS location typically only has one type of shot available. So if you're looking for a specific brand, you may need to click around to a few locations to make your appointment. If you're looking to make an online appointment for a booster shot at a Walgreen's pharmacy, you will only be to able to match your booster to your previous doses for the time being, the company told TODAY. But mix and match is allowed for walk-ins.

Either way, know that there aren't any extra risks related to mixing and matching, Kelen said. Of course, there are the usual risks for temporary side effects (injection site pain, fatigue and other flu-like symptoms, for instance) and the risks for much rarer and potentially more severe side effects (such as heart inflammation with the mRNA vaccines and blood clots after the J&J shot). But, again, those are not extra risks from mixing and matching, they are just the inherent risks from the vaccine itself.

With cases rising again, boosters are a crucial tool in this stage of the pandemic

Ultimately, the most important thing is to be as protected as possible — not just for yourself but for those around you and in your community as well. "The vaccinations are a public health measure," Stappenbeck said. "They protect society, that's the key. So that's why everyone should get it." And Kelen agreed: "It's not only about you," he said. It's to protect "all sorts of people," including your loved ones as well as total strangers.

As we head into Thanksgiving and the winter holiday season, getting a booster is important, Camins said. It's also important to follow CDC guidelines about gatherings and to try to keep events small, he said. But the real key isn't getting boosters to the vaccinated, it's vaccinating those who haven't gotten their shots yet — about 30% of the U.S. population. "When people are interested in boosters, it's almost like we're preaching to the choir," he said. "Really, the message should be that the unvaccinated should go get their first and second doses."

But for those who are eligible, boosters offer more protection and a taste of that normalcy that so many of us crave, especially at this time of year. "Life is trying to start up again," Ossola said. "People are having weddings and we're getting into the winter months here. Who knows how things are gonna go?"