A Covid-19 vaccine developed by Chinese Sinovac Biotech was only 50.38% effective in final-stage tests in Brazil, significantly less than previous results showed, according to a statement published by the São Paulo government on Tuesday.
Although the number meets the limit required by global regulators for approval, it is well below the 78% figure announced last week.
This is raising questions about the veracity of the data and fueling skepticism about the apparent lack of transparency regarding Chinese vaccines.
“The Butantan Institute and the Government of São Paulo inform that the coronavirus vaccine reached 50.38% of general effectiveness in the clinical study conducted in Brazil, in addition to the [an efficacy rate of] 78% for mild cases and 100% for moderate and severe cases of Covid-19. All rates are higher than the 50% required by WHO (World Health Organization) ”, says the statement released Tuesday.
The results of the reduction in shaving speed for regulatory approval should cause concern among scientists, since last week the Brazilian Institute released partial results of “clinical effectiveness” celebrating 78% to 100% effectiveness in preventing infections. The vaccine was studied in 12,500 volunteers, all health professionals, throughout Brazil.
Why the data has changed: In the summary of the clinical study published by the government of São Paulo and by the Butantan Institute, data from another group of participants who reported “very mild” cases of infection were included, resulting in less vaccine effectiveness.
“Regarding the overall effectiveness of the analysis, we met the requirements of the World Health Organization with 50.38%,” said Ricardo Palacios, medical director of clinical research at the Butantan biomedical center in São Paulo, at a news conference.
Questions about effectiveness: However, on Tuesday, senior officials from the Brazilian Ministry of Health told CNN Brasil, affiliated with CNN, that “effectiveness is borderline” and that, for “being on edge”, they would need the health regulatory agency of the municipality, ANVISA, to evaluate.
A Sinovac representative said the company is discussing the result, but declined to comment.
Last week, Anvisa told Instituto Butantan that, in order to approve the emergency use of a vaccine, the global efficacy index needed to be released to the public – information that the institute did not receive from Sinovac at the time, according to sources from CNN Brasil.