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Booster shots are back in the news. A US Food and Drug Administration advisory panel on Thursday approved boosters for certain recipients of the two-shot Moderna vaccine. On Friday, it will consider booster shots for those who got the one-shot Johnson & Johnson vaccine. It will take several more steps, but if all goes smoothly, shots could soon be going into some people’s arms. Booster shots have already been approved for certain recipients of the Pfizer two-shot vaccine.

But will everyone need to get the same brand of shot for their booster as they did for their original shots? Maybe not. The idea of “mixing and matching” shots has been the subject of new research and is being discussed by federal regulators this week. Here, compiled from Globe wire and major media reports, is where the mix and match issue stands now.

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The latest study

A National Institutes of Health study released in preprint form Wednesday looked at what happened when recipients of all three vaccines, Pfizer, Moderna, and Johnson & Johnson, received boosters from the other companies.

“A substantial increase in neutralizing antibody titers was observed in all study participants following booster vaccination irrespective of booster and primary vaccine series,” the study said. “These data suggest that ... an immune response will be generated regardless of the primary COVID-19 vaccination regimen.”

John Beigel, associate director for clinical research in the Division of Microbiology and Infectious Diseases at the National Institute of Allergy and Infectious Diseases, who worked on the study, told The Washington Post that the main finding was that it appears booster doses can be used interchangeably and safely, regardless of what the primary vaccination was.

Which is the best shot to add to your two-shot regimen? “I would be hesitant to say one is better than the other. Our study was never designed to do that,” Beigel said.

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The study’s caveats

The study had a number of limitations, including small size (458 people) and short-term follow-up. It also only measured antibody levels, which are easier to evaluate than other parts of the immune system, and did not look at whether someone got infected.

What’s happening this week

The mix and match research is expected to be discussed Friday at a meeting of the FDA’s Vaccines and Related Biological Products Advisory Committee. “A study sponsored by the National Institute of Allergy and Infectious Diseases evaluating the immunogenicity of each of the vaccines following immunization with the same or a different primary series will be presented. Such heterologous boosting data may be of interest to various stakeholders,” committee meeting materials noted.

What mix and match might mean for Johnson & Johnson recipients

The FDA panel is also expected on Friday to consider Johnson & Johnson booster shots for Johnson & Johnson recipients - and some experts believe it will be greenlighted.

But the new study raises questions about whether Johnson & Johnson recipients might be better off switching to Moderna or Pfizer for their boosters.

The researchers found that those who got a Johnson & Johnson shot followed by a Moderna booster saw their antibody levels rise 76-fold within 15 days, whereas those who received another dose of Johnson & Johnson saw only a fourfold rise in the same period. A Pfizer-BioNTech booster shot raised antibody levels in Johnson & Johnson recipients 35-fold.

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“At the end of the day, folks having the Johnson & Johnson should probably get an mRNA booster,” Scott Hensley, an immunologist at the University of Pennsylvania who was not involved in the new study, told The New York Times. “It’s just a matter of, how much data does the FDA need before making that recommendation?”

“If there’s one [booster] dose, should you get the one with the highest antibody? I’d probably say either of the two mRNA vaccines,” Kathryn M. Edwards, professor of pediatrics in the division of infectious diseases at Vanderbilt University School of Medicine, told the Post.

The road ahead

While the FDA panel will discuss the mix and match concept on Friday, it won’t make a decision. And it’s not clear how the government would go about approving mixing and matching.

STAT News reports that companies typically ask regulators for approval of the use of their shots, but they’re not likely to ask to have a rival’s vaccine used as a booster.

Norman Baylor, president and CEO of Biologics Consulting and a former head of the FDA’s Office of Vaccines, told STAT that the US Centers for Disease Control and Prevention could recommend that mixing and matching of vaccines through what’s called a “preferential recommendation.” But, the news site reported, by the time there’s enough data to make such a recommendation, most people who are due for a booster shot will have already had one.

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Material from Globe wire services was used in this report.


Martin Finucane can be reached at martin.finucane@globe.com.