The COVID-19 vaccine developed jointly by the University of Oxford and AstraZeneca has shown 76% effectiveness against symptomatic COVID-19 for up to 3 months after receiving a single dose. Effectiveness goes up if a second dose is administered in 12 weeks time, which is consistent with a recent change by the British government to lengthen the time between doses. One element still lacking is data on effectiveness among older populations who see their doses spaced by 12 weeks. These results have not yet been peer reviewed.