Sinovac in China delays Covid-19 vaccine study results

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

Scientists following the vaccine have hoped that CoronaVac will be comparable to other Covid-19 vaccines that have been shown to be up to 95% effective.

“It was very frustrating … this is the only vaccine we have right now on Brazilian soil,” said Luiz Carlos Dias, part of a Covid-19 working group of researchers at the University of Campinas in São Paulo. . “I’m worried that the effectiveness rate is probably not that high after all.”

Other researchers said they were not concerned, dismissing the delay as a simple contractual issue. “It’s an anticlimax, it must have happened because Sinovac forbade them to announce the result, most likely because it’s just the result of a country,” said Carlos Fortaleza, an epidemiologist at São Paulo State University.

Although Mr Covas said he could not announce the results of the study, he said CoronaVac had exceeded the 50% efficiency threshold, which means regulators could give it the green light to use.

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

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

With the disease largely under control at home, Chinese vaccine manufacturers have moved to other countries to conduct clinical trials.

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

Mr Covas said more than 200 volunteers in the phase 3 study had contracted Covid-19, allowing scientists to calculate the effectiveness rates of CoronaVac, seeing how many people took the vaccine or placebo. For definitive results, researchers expected at least 154 volunteers to contract Covid-19, but that figure was quickly surpassed as the disease returned to Brazil in recent weeks, following previous declines.

Trials for CoronaVac in Turkey and Indonesia are still ongoing.

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

and jointly by Pfizer Inc.

and BioNTech SE that have been shown to have efficacy rates of 94.5% and 95% in the final stages of testing, respectively. Unlike these two vaccines, new types of genetically coded vaccines, CoronaVac is one of many traditional virus-based vaccines that use a killed or weakened form of the target virus to induce an immune response.

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

The São Paulo government plans to use the vaccine to immunize the state, which hosts a fifth of Brazil’s population, by the end of July. Butantan also plans to start shipping CoronaVac in May to Argentina, Bolivia, Colombia, Honduras, Peru and Uruguay.

“It is much easier logistically to introduce vaccines from Brazil than from China,” Colombian Health Minister Fernando Ruiz said in an interview. Colombia, like most countries in the region, does not have the capacity to produce its own vaccines. The Philippines has also been in negotiations with Sinovac.

—Kejal Vyas of Bogota, Colombia, contributed to this article.

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