CoronaVac has overall efficacy of 50.4 percent, says Butantan

According to data released by the São Paulo state government, the overall efficacy rate of CoronaVac — the Covid-19 vaccine developed by São Paulo’s Butantan Institute and Chinese pharmaceutical company Sinovac — is 50.4 percent, just above the 50 percent required for regulatory approval.

The São Paulo administration, led by Governor João Doria, had initially reported that the vaccine had 78 percent efficacy. However, this figure only related to a portion of the clinical trial volunteers, with the 22 percent in this case being patients who developed mild Covid-19 infections which required medical treatment.

The 50.4 percent figure is the overall efficacy of the vaccine, including asymptomatic cases among the 13,060 trial volunteers in Brazil. Butantan has now included this information in its request for emergency approval submitted to health regulators. The Brazilian government has already purchased 46 million doses of the vaccine, with the option to buy another 54 million.

The Butantan Institute ensures that CoronaVac is 100 percent effective in its prevention of severe cases of Covid-19. 

While experts are buoyant about the overall efficacy of CoronaVac, the bungled presentation of data — attributed to disagreements with data from Chinese partners Sinovac — only serves to fuel the political controversy surrounding the vaccine. President Jair Bolsonaro has been opposed to CoronaVac from the beginning, fearing that a successful vaccination campaign in São Paulo would overshadow his re-election bid in 2022, with Mr. Doria reaping the rewards. Meanwhile, the São Paulo governor has pushed for vaccination to begin as soon as possible, going some way toward explaining the premature disclosure of inaccurate efficacy rates.

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