The so-called interim analysis looked at the first 94 confirmed cases of Covid-19 among the more than 43,000 volunteers who got either two doses of the vaccine or a placebo. It found that fewer than 10% of infections were in participants who had been given the vaccine. More than 90% of the cases were in people who had been given a placebo.

Pfizer said that the vaccine provided protection seven days after the second dose and 28 days after the initial dose of the vaccine. The final goal of the trial is to reach 164 confirmed cases of coronavirus infection.