U.K. will test 'mix and matching' COVID-19 vaccines next year

Britain began administering Pfizer's COVID-19 vaccine to the public Tuesday morning, and assuming U.K. regulators approve another vaccine in the near future, scientists will soon start testing different combinations of vaccines rather than just two shots of the same one, British officials said. The mRNA vaccines from Pfizer and Moderna work differently than a vaccine produced by Oxford University and AstraZeneca, and the goal is to produce the most robust immune response.

"Mix and matching" vaccines, or a heterogeneous boost approach, is "an established process," Kate Bingham, the outgoing head of Britain's vaccine task force, said Tuesday. "It's not being done because of supplies," but rather "trying to trigger the immune response and the durability." Oxford's vaccine, made from a modified chimp cold virus, prompts a strong T-cell response, while the Pfizer and Moderna vaccines trigger larger antibody responses.

"So you do a prime with one vaccine and then the second — whether it's 28 days or two months or whatever the agreed periods would be — would be with a different vaccine," Bingham said. Trials of the Oxford-AstraZeneca vaccine, for example, showed a big boost in efficacy if volunteers were given a half-dose of the vaccine first, then a full dose, versus two full doses.

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