Jon Cohen, Sofia MoutinhoScience’s COVID-19 reporting is supported by the Pulitzer Center and the Heising-Simons Foundation.In the third in a series of conflicting announcements about a Chinese-made COVID-19 vaccine candidate, Brazilian researchers reported today that the results of their efficacy trial were less impressive than they claimed last week.
When analyzed by stricter criteria than used earlier, the vaccine’s efficacy against all forms of COVID-19, including mild cases, dropped from about 78% to 50%.The vaccine still appeared to give nearly 100% protection against disease severe enough to require hospitalization, although the trial amassed too few of those cases for that result to reach statistical significance.