So does getting a dose of Pfizer vaccine after getting a single dose of Johnson & Johnson’s vaccine trigger production of more antibodies than a second dose of the J&J would? Are the messenger RNA vaccines made by Pfizer and Moderna virtually interchangeable, or does switching even there produce a broader set of immune responses?
Is it possible that any combination of vaccine types or brands will work as well — or better — than if the shots were all of a single brand? That’s not yet clear, but it’s possible — even likely — that the combinations and the order in which the vaccines are given will matter.
“A followed by B may not be the same as B followed by A,” explained [Rockefeller Foundation’s] Bruce Gellin.
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A number of small studies done in Europe have shown that following up AstraZeneca’s adenovirus-vectored vaccine with a Pfizer or a Moderna mRNA booster elicits a greater immune response than what is seen from two doses of the AstraZeneca alone. But an ongoing research effort at Britain’s University of Oxford comparing Covid vaccine combinations called the Com-CoV trials suggests that the inverse may not be true.
