PFE Pfizer Inc

By Jared S. Hopkins 

Covid-19 vaccines from Moderna Inc. and from Pfizer Inc. and partner BioNTech SE are highly effective in preventing infections in real-world conditions, federal health officials said, further evidence that vaccinations can slow the spread of the virus.

The vaccines were 90% effective at reducing the risk of infection two weeks after a second dose, according to a study of nearly 4,000 healthcare workers, first responders and other essential workers published by the U.S. Centers for Disease Control and Prevention on Monday.

In addition, the data indicated the vaccines can reduce the risk of coronavirus infections whether or not they cause symptoms, the CDC said.

"This study shows that our national vaccination efforts are working," CDC Director Dr. Rochelle Walensky said. "The authorized vaccines are the key tool that will help bring an end to this devastating pandemic."

The findings are in line with real-world results of the two vaccines in the U.K. and Israel.

They are also consistent with results from clinical trials run by the companies that found the mRNA vaccines to be highly effective at protecting against symptomatic Covid-19. The companies are still conducting their own analyses of whether the vaccines reduce asymptomatic transmission.

The CDC study looked at 3,950 volunteers in six states over 13 weeks from Dec. 14, 2020, to March 13, 2021.

Study subjects swabbed their noses themselves weekly, regardless of whether they had developed symptoms. Then CDC researchers tested the swabs for signs of infection.

About 11% of infections didn't result in symptoms, though 58% of the infections occurred in people whose infections were identified by testing before they developed symptoms or knew they were infected, according to the study.

Researchers reported three infections across 2,479 people who were fully vaccinated, having received two doses several weeks apart. There were eight infections among 477 people who received one dose.

There were no deaths, the CDC said.

The Pfizer-BioNTech vaccine is cleared for use in people 16 years and older, while Moderna's vaccine is authorized for adults 18 years and up.

Write to Jared S. Hopkins at jared.hopkins@wsj.com

(END) Dow Jones Newswires

March 29, 2021 13:36 ET (17:36 GMT)

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