Pfizer and BioNTech say their vaccine is 91% effective against COVID-19, citing new test data

Pfizer and BioNTech said Thursday that their COVID-19 vaccine is "highly effective" after a new study showed it is more than 91% effective in preventing the disease.

The study is based on more than 46,000 trial participants, the companies said on Thursday. Among those participants, there were 927 confirmed symptomatic cases of COVID-19, with 850 cases of COVID-19 in the placebo group and 77 cases recorded among people who received the vaccine. Pfizer announced in a news release that the vaccine is 91.3% effective for people beginning one week after they got their second dose. The latest study data comes one day after Pfizer said its COVID-19 vaccine is safe and strongly protective in children as young as 12, a step toward possibly beginning shots in that age group before they head back to school in the fall. Pfizer and BioNTech in the coming weeks plan to ask the U.S. Food and Drug Administration and European regulators to allow emergency use of the shots starting at age 12.