COVID-19 — Worldwide/Unknown
Background
On [18 Dec 2020], the US Food and Drug Administration issued an emergency use authorization (EUA) for the Moderna COVID-19 vaccine, adding to the earlier EUA for the Pfizer-BioNTech COVID-19 vaccine. Although trial evidence for both vaccines indicates partial protection against COVID-19 illness after 1 dose (1,2), the vaccines are authorized only as 2-dose series and have not yet been evaluated for single-dose use. In the United States, distribution plans for initial supply of
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