A leading Chinese Covid-19 vaccine developed by Sinovac Biotech was just 50.38% effective in late-stage trials in Brazil, significantly lower than earlier results showed, according to a statement published by the government of Sao Paulo Tuesday.
While the number just exceeds the threshold required for regulatory approval, it falls far below the 78% previously announced, raising questions as to the veracity of the data and fueling skepticism over the apparent lack of transparency regarding Chinese vaccines.
"The Butantan Institute and the Government of Sao Paulo report that the coronavirus vaccine achieved a 50.38% overall efficacy rate in the clinical study conducted in Brazil, in addition to (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% level required by the WHO (World Health Organization)," the statement released Tuesday said.
The Brazilian state body financed the phase 3 trials of the vaccine -- known as CoronaVac -- which involved 13,000 health workers across eight Brazilian states.
On Tuesday, high-ranking members of the Brazilian Health Ministry told CNN affiliate CNN Brasil that "the effectiveness is borderline," and that because it was "at the limit," they would need to wait for the evaluation by the country's health regulatory agency ANVISA.
Sinovac Biotech has confidence in its vaccine, it told CNN in a statement on Wednesday.
In response to a question about why there are so many different efficacy rates reported, the company said: "The results are from different populations, in different places with different morbidity rates, and therefore they span a relatively large range."
The final efficacy rate of the vaccine will be determined by China's drug regulator, the National Medical Production Administration, according to the representative.
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