A 3-month interval between doses of the Oxford COVID-19 vaccine results in higher vaccine efficacy than a 6-week interval, with the first dose offering 76% protection in the 3 months between doses. These results, from post-hoc exploratory analyses from a phase 3 randomised controlled trial published in The Lancet, suggest that the interval between doses can be safely extended to 3 months given the protection a single dose offers, which may allow countries to vaccinate a larger proportion of the population more rapidly.