Mixing and matching COVID-19 vaccines for booster doses appears safe and as effective—if not more effective—than sticking with the same vaccine for a booster dose. That’s according to preliminary data posted online Wednesday from a clinical trial run by the National Institutes of Health.
The trial bolsters what some have long hoped: that mixing and matching vaccines could provide stronger, broader protection against the pandemic virus and all its variants.
The trial was not large enough to definitively indicate which combination of vaccines offers the best protection. And the early results, available on a preprint server, have not yet been peer-reviewed. But the preliminary trial findings do hint that Moderna’s mRNA vaccine may offer the strongest protection all around—backing up similar findings from earlier vaccine-effectiveness studies. The data also suggests that people who received the one-shot Johnson & Johnson vaccine may want to get a boost with one of the two mRNA vaccines, either Moderna’s or Pfizer/BioNTech’s.
But most clearly, the study found that mix-and-match boosting increases protection and produces only similar side effects as boosting with the same vaccine. Or, in the authors’ words: “These data suggest that if a vaccine is approved or authorized as a booster, an immune response will be generated regardless of the primary Covid-19 vaccination regimen.”