From the Journals

Mixing COVID vaccine boosters may be better option: Study


Increase in antibodies

But all the groups saw substantial increases in their antibody levels, which is thought to indicate that they were better protected.

Overall, groups that got the same vaccine as their primary series saw 4 to 20-fold increases in their antibody levels. Groups that got different shots than the ones in their primary series got 6 to 76 fold increases in their antibody levels.

People who had originally gotten a Johnson & Johnson vaccine saw far bigger increases in antibodies, and were more likely to see a protective rise in antibodies if they got a second dose of an mRNA vaccine.

Dr. Schaffner noted that European countries had already been mixing the vaccine doses this way, giving people who had received the AstraZeneca vaccine, which is similar to the Johnson & Johnson shot, another dose of an mRNA vaccine.

German Chancellor Angela Merkel received a Moderna vaccine for her second dose after an initial shot of the Oxford-AstraZeneca vaccines, for example.

No safety signals related to mixing vaccines has been seen in countries that routinely use the approach for their initial series.

A version of this article first appeared on


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