By Eduardo Simões
SAO PAULO (Reuters) – A coronavirus vaccine developed by China’s 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.
The latest results are a major disappointment for Brazil, as the Chinese vaccine is one of two that the federal government has set up to begin immunizing during the second wave of the world’s second deadliest COVID-19 outbreak.
Several scientists and observers exploded the Butantan Biomedical Center a few days ago because they released partial data that caused unrealistic expectations. The confusion could contribute to skepticism in Brazil about the Chinese vaccine, which criticized President Jair Bolsonaro and questioned the ‘origin’.
“We have a good vaccine. Not the best vaccine in the world. Not the ideal vaccine,” said microbiologist Natalia Pasternak, criticizing Butantan’s triumphant critique.
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 received the vaccine that did not require clinical help.
Ricardo Palacios, medical director for clinical research at Butantan, said Tuesday that the new finding on lower efficacy contains data on the “very mild” cases.
“We need better communicators,” said Gonzalo Vecina Neto, a professor of public health at the University of Sao Paulo and former head of Brazilian health regulator Anvisa.
Piece flour disclosures about Chinese vaccine trials worldwide have expressed concern that they are not subject to the same public scrutiny as American and European alternatives.
Palacios and officials in the Sao Paulo state government, which funds Butantan, stressed the good news that none of the volunteers vaccinated with CoronaVac had to be hospitalized with COVID-19 symptoms.
Public health experts said it would only be a relief for Brazilian hospitals suffering from rising property taxes. However, it will take longer to curb the pandemic with a vaccine that makes as many mild cases as possible.
“It’s a vaccine that starts the process of overcoming the pandemic,” Pasternak said.
DELAYS AND DISAPPOINTMENT
Investigators from Butantan delayed the announcement of their results three times and blamed a confidentiality clause in a contract with Sinovac.
Meanwhile, Turkish researchers said last month that CoronaVac was 91.25% effective on an interim analysis. Indonesia approved the use of vaccine emergency use on Monday based on interim data showing that it is 65% effective.
Butantan officials said the design of the Brazilian study, which focuses on leading health workers during a serious outbreak in Brazil and older elderly people, makes it impossible to directly compare the results with other trials or vaccinations.
Nevertheless, COVID-19 vaccines used by Pfizer Inc in partnership with partner BioNTech SE and Moderna Inc were approximately 95% effective in preventing late-stage nuclear disease.
The disappointing CoronaVac data is the latest setback for vaccination efforts in Brazil, where more than 200,000 people have died since the outbreak began – the worst death toll outside the United States.
Brazil’s national vaccination program is currently dependent on CoronaVac and the vaccine developed by the University of Oxford and AstraZeneca Plc, and none of them have approved regulations in Brazil.
Anvisa, which has set an efficiency rate of at least 50% for vaccines in the pandemic, has already pushed Butantan for more details about its study, after applying for emergency consent on Friday.
AstraZeneca failed to deliver active ingredients to Brazil over the weekend, prompting the government to scramble to import finished doses of the vaccine from India to begin vaccinations.
(Reporting by Eduardo Simoes; Additional reporting by Gabriel Stargardter and Pedro Fonseca; Editing by Brad Haynes and Bill Berkrot)