Sinovac in China delays Covid-19 vaccine trial 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 effectiveness of the vaccine, which is expected to be one of the first approved for use in Brazil.

Scientists following the vaccine had hoped that CoronaVac would be comparable to other Covid-19 vaccines that were found to be 95% effective.

“It was very frustrating… it’s the only vaccine we have on Brazilian soil at the moment,” said Luiz Carlos Dias, member of a Covid-19 working group of researchers at the University of Campinas in the State of São Paulo. “I’m worried that the efficiency rate might not be that high after all.”

Other researchers said they weren’t affected, dismissing the delay as a mere contractual issue. “It’s an anti-limit, it must have happened because Sinovac forbade them to announce the result, most likely because it was only the result of one country,” said Carlos Fortaleza, epidemiologist at São Paulo State University.

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

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

Sinovac, a private Beijing-based company that has also developed vaccines against hepatitis A and B, the H5N1 avian influenza 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 makers have turned to other countries for clinical trials.

Brazil has proven to be an ideal testing ground. Covid-19 has ravaged the country of Latin America, killing nearly 190,000 people, just behind the United States. The advantage of the dismal 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 of the volunteers in the Phase 3 trial had contracted Covid-19, allowing scientists to calculate the effectiveness rates of CoronaVac by seeing how many of those people had taken the vaccine or the placebo. For definitive results, researchers expected a minimum of 154 volunteers to contract Covid-19, but that figure was quickly exceeded when the disease returned to Brazil in recent weeks after previous declines.

CoronaVac trials in Turkey and Indonesia are still ongoing.

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

and jointly by Pfizer Inc.

and BioNTech SE which showed 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 around 36 and 46 degrees Fahrenheit, making it easier to transport and store in poorer and less developed countries. infectious disease specialists said.

The São Paulo government plans to use the vaccine to immunize the state, which is home to one-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’s logistically much easier to get 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 entered into negotiations with Sinovac.

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

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