Can COVID-19 Vaccines Be Mixed and Combined? Health experts say the two doses should be of the same vaccine.
Currently, coronavirus vaccines being developed in the United States, Great Britain and other parts of the world require two doses a few weeks apart.
In the United States, where Pfizer-BioNTech and Moderna are distributed, health authorities say the vaccines are not interchangeable. In Britain, where Pfizer-BioNTech and AstraZeneca and the University of Oxford are used, officials say doses should be consistent.
But in the unlikely scenario where the same type is not available or is unknown which was used first, the UK authorities say it is okay to inoculate the one available in the second dose. Since the two given there work in the same way, they argue that it is better to combine mismatched doses than the partial protection that the first injection would provide.
But in the absence of studies, vaccine doses should not be mixed, said Naor Bar-Zeev, a vaccine expert at Johns Hopkins University.
If people accidentally get a different vaccine in the second dose than the first, it is likely “that it will work well and be well tolerated,” but evidence is needed to be sure, Bar-Zeev added.