Interim results of two large randomized, placebo-controlled trials (RCTs) demonstrate ~95% relative efficacy in preventing COVID-19 (Pfizer, Moderna). The AstraZeneca/Oxford vaccine has ~70% relative efficacy. Absolute benefits will vary with baseline risk and time but if annual risk of developing COVID-19 is 20%, then vaccine would decrease risk to 1% (6% with AstraZeneca/Oxford). These vaccines appear safe and may decrease the likelihood of severe COVID-19. Ongoing studies should provide further details.