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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 six months after people get 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. 

Currently, the vaccine is being administered in the U.S. under emergency use authorization from the Food and Drug Administration, and it is only permitted for use in people over the age of 16. But the new study findings means the companies will apply for formal approval from the federal government.

"These data confirm the favorable efficacy and safety profile of our vaccine and position us to submit a Biologics License Application to the U.S. FDA," said Pfizer CEO Albert Bourla in a statement. 

Pfizer study finds COVID-19 vaccine is 100% effective, safe for kids 12 to 15 06:48

Bourla added, "The high vaccine efficacy observed through up to six months following a second dose and against the variant prevalent in South Africa provides further confidence in our vaccine's overall effectiveness."

The analysis also found that the vaccine was 100% effective in preventing COVID-19 cases in South Africa, where the coronavirus variant B.1.351 is prevalent. 

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