Brazilian researchers testing China’s Sinovac vaccine said on Tuesday that full data showed it was 50.38% effective against Covid-19 in late-stage studies, nearly 30 percentage points lower than previously announced as concerns grew. on the transparency of the study.
The Butantan Institute in São Paulo said last week that late-stage studies have shown that the CoronaVac vaccine is between 78% and 100% effective, providing total protection against severe cases of the disease.
However, after increasing pressure from scientists, some of whom accused the trial organizers of misleading the public, Butantan said the rates included only volunteers who had suffered mild to severe cases of Covid-19. . When data from all volunteers are taken into account, including those who contracted “very mild” cases of Covid-19 and did not need medical care, the overall effectiveness rate drops to 50.38%, Butantan said on Tuesday.
Despite having one of the lowest efficacy rates for any new coronavirus vaccine, CoronaVac is still more effective than some flu vaccines and can be stored cheaply in a regular refrigerator, making it a viable option for developing countries. public health experts said.
However, the fragmented and unorthodox announcement of the effectiveness rate of CoronaVac, which was scheduled to be announced for the first time last month, risks damaging the credibility of a vaccine that many Brazilians are already reluctant to take, doctors said.