Sao Paulo — A Covid-19 vaccine developed by Chinese pharmaceutical firm Sinovac Biotech was found to be more than 50% effective in a Brazilian clinical trial, though researchers delayed releasing more information at the request of the company.

A 50% efficacy rate is a minimum standard set by US regulators for emergency authorisation of Covid vaccines. Messenger RNA vaccines from Moderna and Pfizer Inc. have produced far better results, reducing symptomatic Covid cases by well over 90% in giant trials.

The late-stage trial of Sinovac’s vaccine in Brazil, involving about 13,000 participants, suggested the shot is “safe and effective,” authorities at the Butantan Institute and from the state of Sao Paulo said. They were asked to not disseminate the information until it was thoroughly reviewed in China as part of a contractual agreement, they said.

“Our goal was for the shot to be more than 50% effective,” state health secretary Jean Gorinchteyn said at a press conference. “A vaccine that reaches at least that is already cause for celebration.”

The group that received the vaccine in Brazil’s trial had no severe cases of Covid-19, and the main side effect reported was mild pain at the injection site, said Dimas Covas, head of Butantan. Efficacy is above the threshold needed for vaccine to be registered by Brazil health regulator known as Anvisa, which still has to approve the shot, he said.

The trial produced efficacy data that differed from tests carried out in other countries, Gorinchteyn said, without elaborating. He added that Sinovac’s review of the data is slated to take 15 days but could take less than that, and should not delay the planned January 25 start of inoculations with the Sinovac shot.

“Sinovac has several ongoing trials, and it’s important it gives the data consistency,” Covas said. “The company can’t analyse data from the same vaccine using different criteria, and can’t have three different efficacy rates for the same vaccine.”

A successful vaccine would enable Sinovac to inoculate more people around the world and save lives, especially in developing countries like Brazil that will have limited access to the Pfizer and Moderna shots. Vaccines from Sinovac and other Chinese companies could also help their home country win geopolitical influence and restore an image tarnished by the criticism of its initial response to the virus.

Sinovac is also running trials in Indonesia and Turkey.

The rationale for the delay in reporting the results was murky. It is routine for trials of a drug or vaccine conducted in different groups of patients or locations to produce slightly different results, and research groups typically report results of independent trials separately.

While Butantan and state authorities reiterated their optimism for the shot, the data delay is a blow to Sao Paulo governor Joao Doria’s plan to obtain swift approval and begin vaccinating the state of 45-million people in January. He is trying to move quickly while the central government drags its feet on supply agreements and concrete vaccination dates. Millions of doses of Sinovac’s vaccine, called CoronaVac, have already been shipped to Sao Paulo.

Sinovac’s shot is potentially more suited to developing countries because it can be kept at normal refrigerator temperatures. By contrast, the mRNA vaccines from Pfizer and Moderna require deep-freeze conditions for storage and transportation, making distribution more complicated.

The Sinovac vaccine has been at the centre of a political dispute between Doria and President Jair Bolsonaro, who says a vaccine from China cannot be trusted. Bolsonaro, who does not plan to take any coronavirus vaccine after being infected earlier this year, has openly bickered with Doria, seen as a contender for presidential elections in 2022.

In addition to Brazil’s central government, Butantan is in talks to sell the vaccine to Argentina, Uruguay, Peru, Ecuador and Honduras. Chile is in talks directly with the Chinese company, according to Covas.



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