As the first quarter of 2021 draws to a close, we have growing evidence from those countries most advanced in their inoculation programmes that existing COVID-19 vaccines are not only extremely effective at preventing serious disease, they also have an important role to play in reducing asymptomatic infection, and with that disease transmission. Confirmation that results obtained in the field match almost precisely those seen in phase 3 trials gives us greater confidence that, while COVID-19 may continue to restrict…