Can COVID-19 vaccines be mixed and combined?
Health officials say both doses must be of the same vaccine.
COVID-19 vaccines launched in the United States, the United Kingdom and other parts of the world so far require two injections administered a few weeks apart.
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In the United States, where Pfizer and Moderna vaccines are being distributed, health officials say the vaccines are not interchangeable. In England, where doses of Pfizer and AstraZeneca are available, the authorities also say that the doses must be consistent.
But in the rare case that the same type is not available or if what was given in the first injection is not known, the British authorities say that it is okay to give any vaccine available for the second injection. Because the Pfizer and AstraZeneca vaccines work similarly, they say that an incompatible dose is better than partial protection.
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But without any studies, doses of the vaccine should not be mixed, said Naor Bar-Zeev, a vaccine expert at Johns Hopkins University.
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If people happen to get a different vaccine for their second injection by accident, Bar-Zeev said it is likely to “work well and be well tolerated”, but evidence is needed to be sure.