China’s Sinovac Delays Results of Covid-19 Vaccine Research

“There cannot be three efficacy results for the same vaccine,” said Butantan’s director, Dimas Covas. He said the delay had nothing to do with the effectiveness of the vaccine, which is expected to be one of the first to be approved for use in Brazil.

Scientists following the vaccine had hoped that CoronaVac would be comparable to other Covid-19 vaccines that have been shown to be as much as 95% effective.

“It was very frustrating… this is the only vaccine we currently have on Brazilian soil,” said Luiz Carlos Dias, part of a Covid-19 working group of researchers at the University of Campinas in São Paulo state. “I’m afraid the efficacy might not be that high after all.”

Other investigators said they were not concerned and dismissed the delay as a purely contractual matter. “It’s anti-climactic, it must have happened because Sinovac forbade them to disclose the result, most likely because it’s only the result of one country,” said Carlos Fortaleza, an epidemiologist at São Paulo State University.

Although Mr Covas said he couldn’t announce the results of the trial, he said CoronaVac had passed the 50% efficacy threshold, meaning regulators could give the green light for use.

The Wall Street Journal first reported on Monday that Phase 3 results showed that CoronaVac had exceeded the 50% threshold set by international scientists for a vaccine to be considered viable.

Sinovac, a private Beijing company that has also developed vaccines against hepatitis A and B, the H5N1 avian flu virus and the H1N1 swine flu virus, did not immediately respond to requests for comment.

With the disease largely under control at home, China’s vaccine makers have turned to other countries to conduct their clinical trials.

Brazil has proven to be an ideal testing ground. Covid-19 has ravaged the Latin American country, killing nearly 190,000 people, second only to the U.S. The benefit of the grim statistics is that the country has been able to test vaccines much faster than countries where Covid-19 is under control is.

Mr Covas said more than 200 of the Phase 3 volunteers were contracted to Covid-19, which allowed scientists to calculate CoronaVac’s efficacy rates by seeing how many of those people were taking the vaccine or the placebo. For definitive results, researchers waited for a minimum of 154 volunteers to contract Covid-19, but that figure was quickly surpassed when the disease returned to Brazil in recent weeks after previous declines.

The trials for CoronaVac in Turkey and Indonesia are still ongoing.

Brazilian infectious disease specialists following the development of CoronaVac hope for results comparable to those of the vaccines being developed by Moderna Inc.

and jointly by Pfizer Inc.

and BioNTech SE which have been shown to have an efficacy of 94.5% and 95% respectively in the final test phases. In contrast to those two vaccines, new types of vaccines with a genetic code, CoronaVac is one of many traditional virus-based vaccines that use a killed or attenuated form of the target virus to elicit an immune response.

While these more traditional vaccines tend to have lower efficacy, CoronaVac can be stored in a standard refrigerator between about 36 and 46 Fahrenheit, making it easier to transport and store in poorer and less developed countries, infectious disease specialists say .

The São Paulo government plans to use the vaccine by the end of July to vaccinate the state, where one-fifth of Brazil’s population lives. Butantan also plans to ship CoronaVac to Argentina, Bolivia, Colombia, Honduras, Peru and Uruguay in May.

“It is logistically a lot easier to bring the vaccines from Brazil than from China,” Colombian Health Minister Fernando Ruiz said in an interview. Colombia, like most countries in the region, has no capacity to produce its own vaccines. The Philippines is also negotiating with Sinovac.

—Kejal Vyas in Bogotá, Colombia, contributed to this article.

Write to Samantha Pearson at [email protected] and Luciana Magalhaes at [email protected]