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China’s Sinovac COVID-19 Vaccine Less Effective than Initially Thought


Outbreak of the coronavirus disease (COVID-19), in Sao Paulo

Late-stage trials in Brazil show the Chinese COVID-19 vaccine Sinovac to be 50.38% effective, nearly 30 percentage points below the initial results released last week.

Instituto Butantan, the São Paulo-based research institute responsible for developing the vaccine and conducting trials in the country, announced last week the vaccine had a 78% overall efficacy, while offering total protection against severe cases. The new trials, which involved 12,508 volunteers, have shown that Sinovac continues to be 100% effective in blocking severe cases.

“This is an efficient vaccine,” Instituto Butantan Chief Researcher Ricardo Palacios said during a press conference Tuesday. “We have a vaccine that is able to control the pandemic through this expected effect, which is the decrease in the disease’s intensity.”

The results come at a moment in which President Jair Bolsonaro’s government has been criticized for the delay in rolling out the vaccine. Neighboring countries, such as Chile with the Pfizer-BioNTech vaccine and Argentina with Russia’s Sputnik V, started their vaccination campaigns weeks ago, while Brazil still does not have a concrete immunization plan a week after the country surpassed 200,000 COVID-19 deaths.

Last week, Bolsonaro’s government closed an exclusive deal with Instituto Butantan for 100 million doses to be distributed by the end of 2021. The vaccine, however, still needs the approval of the Brazilian National Health Surveillance Agency (ANVISA).

Instituto Butantan has included the new results in its emergency request for approval, initially filed Friday. ANVISA requires a 50% effective rate for vaccines, the same percentage recommended by the World Health Organization.

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