A coronavirus vaccine developed by Beijing-based Sinovac Biotech Ltd., was barely 50% effective during late-stage clinical trials in Brazil, significantly less than earlier results reported, a statement from the city government of Sao Paulo said Tuesday.
Previous announcements indicated Sinovac Biotech’s vaccine performed at a rate of 78% overall efficacy. By comparison, the FDA-approved vaccines from Pfizer-BioNTech and Moderna boast rates of 95% and 94.5%, respectively.
“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,” the statement said, CNN reported. “All rates are higher than the 50% level required by the World Health Organization.”
The dip of 78% to 50.38% has raised questions among public health experts about the veracity of the Sinovac Biotech’s data and fuels skepticism over the transparency of Chinese virus vaccines.
Top members of the Brazilian Health Ministry said the Sinovac Biotech’s vaccine’s “effectiveness is borderline” and that is because it was “at the limit,” they would need to wait for the evaluation by ANVISA, the country’s health regulatory agency, CNN’s local affiliate reported.
Sinovac Biotech defended its vaccine Wednesday, saying the differing efficacy rates are “the results from different populations, in different places with different mobility rates, and therefore they span a relatively large range.”
The final vaccine efficacy rate will be decided by China’s drug regulator, the National Medical Production Administration, CNN reported.