The coronavirus vaccine developed by Chinese company Sinovac Biotech was only 50.4% effective in preventing symptomatic infections in a Brazilian trial, researchers said on Tuesday, barely enough for regulatory approval and well below the rate announced last week.
Reuters: The latest results are a huge disappointment for Brazil, as the Chinese vaccine is one of two vaccines that the federal government has lined up to start immunization during the second wave of the second most dangerous outbreak of Covid-19 in the world.
Many scientists and observers criticized the Botantan Biomedical Center for releasing partial statements just days ago that generated unrealistic expectations. Confusion may add to suspicions in Brazil about the Chinese vaccine, which President Jair Bolsonaro has criticized, questioning its “origins”.
“We have a good vaccine. Not the best vaccine in the world,” said microbiologist Natalia Pasternak, criticizing Botantan’s winning rhetoric, “Not the perfect vaccine.”
Last week, Brazilian researchers celebrated results showing 78% efficacy against “mild to severe” Covid-19 cases, a rate they later described as “clinical efficacy.”
They said nothing at the time about another group of “very mild” infections among those who had received the vaccine that did not require medical help.
Ricardo Palacios, medical director of clinical research in Butantan, said Tuesday that the new, less effective results included data on these “very mild” cases.
The sporadic disclosure of Chinese vaccine trials worldwide has raised concerns that they are not subject to the same general scrutiny as US and European alternatives.
Palacios and officials in the state government of São Paulo, which funds Bhutantan, confirmed the good news that none of the volunteers who had been vaccinated with the Coronavirus have been hospitalized due to symptoms of Covid-19.
Public health experts said this alone would be a relief to Brazilian hospitals, which are collapsing under the pressure of soaring case loads. However, it will take longer to curb the epidemic with a vaccine that allows for many mild cases.