Brazilian researchers testing China’s Sinovac vaccine said on Tuesday that complete data showed it was 50.38% effective against Covid-19 in late-stage trials, nearly 30 percentage points lower than previously announced, due to concerns about transparency of the study increases.
The São Paulo-based Butantan Institute said last week that late-stage trials have shown the CoronaVac vaccine to be between 78% and 100% effective, providing total protection against severe cases of the disease.
After increasing pressure from scientists, some of whom accused the organizers of the trial of misleading the public, Butantan said the rates only included volunteers who had Covid-19 to a mild or severe case. When data from all volunteers are considered, including those who have suffered ‘very mild’ cases of Covid-19 and need no medical help, the overall effectiveness drops to 50.38%, Butantan said on Tuesday.
Although CoronaVac has one of the lowest efficacy rates for any new coronavirus vaccine, it 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 said.
However, the pieces and unorthodox announcement of the effectiveness rate of CoronaVac, which was to be announced for the first time last month, could damage the credibility of a vaccine that many Brazilians reluctantly take, doctors said.