You are using an older browser version. Please use a supported version for the best MSN experience.

China Coronavirus Vaccine Only 50% Effective, Researchers Say

U.S. News & World Report logo U.S. News & World Report 1/13/2021 Cecelia Smith-Schoenwalder
BEIJING, Jan. 10, 2021 -- A medical worker inoculates a recipient with a COVID-19 vaccine at Peking University Hospital in Beijing, capital of China, Jan. 10, 2021. Beijing is slated to complete the inoculation for key groups before the Spring Festival, which falls on Feb. 12 this year. (Photo by Ren Chao/Xinhua via Getty) (Xinhua/Ren Chao via Getty Images) © (Xinhua/Ren Chao/Getty Images) BEIJING, Jan. 10, 2021 -- A medical worker inoculates a recipient with a COVID-19 vaccine at Peking University Hospital in Beijing, capital of China, Jan. 10, 2021. Beijing is slated to complete the inoculation for key groups before the Spring Festival, which falls on Feb. 12 this year. (Photo by Ren Chao/Xinhua via Getty) (Xinhua/Ren Chao via Getty Images)

A coronavirus vaccine from China is significantly less effective than previous data suggested, according to researchers conducting trials in Brazil.

Scientists at the state-run Butantan Institute said Tuesday that their trial of the vaccine developed by China's Sinovac showed an efficacy rate of just over 50%.

The rate is significantly lower than the 78% efficacy rate in "mild to severe" cases that institute officials issued last week. Those calculations did not include data from "very mild infections" that did not require medical assistance, the researchers said.

State media in China downplayed the news, with one outlet running the headline "100 percent effective in preventing severe cases, could reduce hospitalizations by 80 percent," according to The New York Times.

The World Health Organization has said that any vaccine with an efficacy rate over 50% would be acceptable, and trials of the vaccine in other countries have produced different results.

But the small margin for regulatory approval could raise questions about the vaccine and hurt confidence.

[ MAP: The Spread of Coronavirus ]

"Regarding the overall efficacy of the analysis, we met the requirements of the World Health Organization with 50.38%," Ricardo Palacios, medical director for clinical research at the Butantan Institute, said Tuesday during a news conference.

But members of the Brazilian Health Ministry told CNN on Tuesday that "we have to wait for ANVISA [Brazilian Health Regulatory Agency] to evaluate."

Turkey on Wednesday approved the vaccine for emergency use, with the country's health minister, Fahrettin Koca, receiving his shot live on television.

Copyright 2021 U.S. News & World Report

AdChoices
AdChoices

More from U.S. News & World Report

U.S. News & World Report
U.S. News & World Report
image beaconimage beaconimage beacon