Results from AstraZeneca’s key US trial of its COVID-19 vaccine, issued by press release on Monday morning, have exceeded experts’ expectations.

In a trial involving more than 32,000 volunteers, about two-thirds of whom received the vaccine, the shots had a 79% efficacy in preventing symptomatic COVID-19. This was based on 141 cases of the disease that occurred across the vaccine and placebo arms of the trial. There were no cases of severe disease requiring hospitalization among people given the vaccine, compared to five in the placebo arm, National Institute of Allergy and Infectious Diseases chief Anthony Fauci said during a White House press conference.