Brazil announces ‘fantastic’ results for Chinese-made COVID-19 vaccine, but details remain sketchy


Brazil, with more COVID-19 cases than any other country after the United States and India, is on the verge of having its first authorized vaccine for the pandemic disease. At a press conference today, Brazilian researchers reported that a vaccine made by a Chinese company, Sinovac, was safe and had 78% efficacy in preventing mild cases of COVID-19 in a study of more than 12,000 health care workers. It also completely prevented moderate and severe illness caused by SARS-CoV-2 infections, the team said. “The result we are seeing today is fantastic,” Rosana Richtmann, a physician from the Emilio Ribas Institute of Infectious Disease, said at the press conference.

Dimas Tadeu Covas, head of the Butantan Institute—a state-owned vaccinemaker that is co-sponsoring the trial—expects Brazil’s regulatory agency to authorize the vaccine, called CoronaVac, for emergency use in the coming days. “We have now all the documentation to make the request,” he says. Brazil also has efficacy trials underway of a COVID-19 vaccine made by AstraZeneca and the University of Oxford and many scientists there expect it, too, to receive authorization soon. But the good news about CoronaVac was overshadowed by complaints that the announcement included little data—and that Sinovac has muzzled its Brazilian collaborators. Indeed, Brazilian researchers had previously held a press conference to announce the vaccine was a success, but were not allowed to give an exact efficacy figure at that time.

Most of the vaccines authorized in other countries rely on high-tech approaches, such as messenger RNA (mRNA) coding for the surface protein of SARS-CoV-2 or a harmless viral vector carrying the gene for that protein—the approach taken by the AstraZeneca-Oxford vaccine. But Sinovac turned to a more established approach. Its vaccine, which is also in efficacy trials in Turkey and Indonesia, relies on the whole coronavirus, chemically crippled so it can’t cause disease. The reported efficacy against mild disease falls short of the roughly 95% achieved by two mRNA vaccines. But the “main purpose” of COVID-19 vaccines, Covas says, is to prevent infected people from progressing to severe disease. A different whole, inactivated SARS-CoV-2 vaccine made by Sinopharm’s China National Biotec Group has nearly identical results, the company reported last week from a large efficacy trial in several Middle Eastern countries.

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