AstraZeneca and Oxford reported on 22 November in separate press releases that an interim analysis of trials in the United Kingdom and Brazil found an “average efficacy” of 70%. Both studies gave volunteers a “prime” first dose and a booster shot at least 1 month later. But the U.K. study compared two different doses for the prime, whereas the Brazilian study only looked at one dose and enrolled people across a wider range of ages. Efficacy ranged from 62% to 90%

Source: After dosing mix-up, latest COVID-19 vaccine success comes with big question mark | Science | AAAS