A single dose of the AstraZeneca/Oxford vaccine offered 76% protection against COVID-19 for 3 months, at which time administering the second dose resulted in up to 47% greater protection than giving it at 6 weeks, according to a study published late last week in the Lancet.The pooled post-hoc exploratory analysis of four randomized, controlled trials led by researchers from Oxford University involved 17,178 adults in the United Kingdom, Brazil, and South Africa from Apr 23 to Dec 6, 2020.The study also examined the effect of one versus two doses of the vaccine in reducing community spread of COVID-19 and the protection conferred by a low dose followed by a standard dose versus two standard doses.Implications for policymakersParticipants who