A Covid-19 vaccine developed by China’s Sinovac Biotech was only 50.38% effective in final-stage trials in Brazil, significantly lower than previous results, according to a statement released Tuesday by the São Paulo government.
While the number meets the threshold required by global regulators for approval, it falls well below the 78% announced last week.
It is raising questions about the veracity of the data and fueling skepticism at the apparent lack of transparency regarding Chinese vaccines.
“The Butantan Institute and the Government of São Paulo report that the coronavirus vaccine achieved an overall efficacy rate of 50.38% in the clinical study conducted in Brazil, in addition to [an efficacy rate of] 78% in mild cases and 100% in moderate and severe cases of Covid-19. All rates are above the 50% level required by the WHO (World Health Organization), ”the statement said on Tuesday.
The primary results for regulatory approval are likely to cause concern among scientists, as last week the Brazilian Institute published partial results of clinical efficacy that held 78% to 100% efficacy in the prevention of ‘infections. The vaccine was studied in 12,500 volunteers, all of them health professionals, throughout Brazil.
Why the data has changed: A summary of the clinical study published by the government of São Paulo and the Butantan Institute includes data from another group of participants who reported “very mild” cases of infection, which gave a rate of lower efficacy for the vaccine.
“As for the overall effectiveness of the analysis, we met the requirements of the World Health Organization with 50.38%,” Ricardo Palacios, medical director of clinical research at the Butantan biomedical center in Sao, said on Tuesday. Paulo, during a press conference.
Efficiency questions: However, on Tuesday, senior members of the Brazilian Ministry of Health told CNN Brazil, affiliated with CNN, that “effectiveness is at the limit” and that, because “it is at the limit,” they would need the health regulatory agency of the United States. county, ANVISA, to evaluate it.
A Sinovac representative said the company is discussing the outcome, but declined to comment further.
Last week, ANVISA told the Butantan Institute that in order to approve the emergency use of a vaccine, the overall efficacy rate had to be disclosed to the public, information the institute did not receive in that moment of Sinovac, according to sources of CNN Brazil.