A vaccine from Sinovac, China, has protected health workers in Brazil from severe COVID-19.
REUTERS / Thomas Peter
By Jon Cohen, Sofia Moutinho
Science‘COVID-19 reporting is supported by the Pulitzer Center and the Heising-Simons Foundation.
Brazil, with more COVID-19 cases than any other country after the United States and India, is about to have its first authorized vaccine for the pandemic. At a press conference today, Brazilian researchers reported that a vaccine made by a Chinese company, Sinovac, is safe and that it is 78% effective in preventing mild cases of COVID-19 in a study among others: 12,000 health workers. It also completely prevented moderate and severe diseases caused by SARS-CoV-2 infections. “The result we are seeing today is fantastic,” Rosana Richtmann, a physician at the Emilio Ribas Institute of Infectious Diseases of São Paulo, told the press conference.
Dimas Tadeau Covas, head of the Butantan Institute – a state-run vaccine manufacturer in São Paulo that co-sponsors the trial – expects the Brazilian regulatory agency to grant the vaccine, called CoronaVac, in the coming days. “We now have all the documentation to submit the request,” he said. Brazil is also conducting efficacy trials with a COVID-19 vaccine made by AstraZeneca and Oxford University, and many scientists there expect it to be authorized soon as well. But the good news about CoronaVac was overshadowed by complaints that the announcement contained little information – and that Sinovac had muzzled his Brazilian associates. Indeed, Brazilian researchers had previously held a press conference to announce that the vaccine was a success, but they could not then give an exact effectiveness.
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Most vaccines authorized in other countries rely on high-tech approaches, such as messenger RNA encoding the surface protein of SARS-CoV-2, or the approach used by the AstraZeneca-Oxford vaccine, which provides a harmless viral vector used which is the gene for that protein. But Sinovac turned to a more established approach. The vaccine, which is also in efficacy trials in Turkey and Indonesia, is dependent on the whole coronavirus, chemically paralyzed so that it cannot cause disease. The reported efficacy against mild diseases does not exceed the approximately 95% achieved by two mRNA vaccines. But the “main goal” of COVID-19 vaccines, Covas said, is to prevent infected people from progressing to serious diseases. Another whole, inactivated SARS-CoV-2 vaccine made by Sinopharm’s China National Biotec Group has almost the same results, the company reported last week from a major efficacy test in several Middle Eastern countries.
Both Sinovac and Sinopharm have kept a tight lid on what their partners could reveal about their vaccines. At the December 23 press conference held at the governor’s residence in São Paulo, researchers said that due to a contractual agreement with Sinovac, they can only report that CoronaVac has more than 50% efficiency, an internationally accepted standard for emergency authorization. Today’s presentation revealed the specific efficacy rate, but researchers were very excited about describing the exact number of people who had vaccines in the vaccines and placebo arms.
In a formal presentation of the data today at Butantan, Covas did not mention any case numbers, saying the data will be reported in a scientific publication and to the Brazilian regulators. But when pushed by journalists, he admitted there were 218 cases of mild illness. “The exact number is 160 in the placebo group and less than 60 in the vaccinated group,” he said. (That would equate to 63%, not 78%, of efficiency.) CoronaVac seems to have worked just as well in the elderly as in other age groups, the researchers added.
The lack of data – let alone the difference in efficiency – predictably led to immediate skepticism. “Until they show us these numbers, it’s nothing but a blank announcement,” tweeted epidemiologist Denise Garrett, vice president of the nonprofit Sabin Vaccine Institute.
Details are lacking in the initial announcements of efficacy trials by other COVID-19 vaccine manufacturers. But a researcher who runs one of the 16 websites conducting the CoronaVac trial in Brazil, Esper Kallas of the University of São Paulo, said that even investigators do not yet know all the data. Kallas, who spoke to Science said after the press conference that he was “happy” about the results. “We know the 78% is true.” But he is frustrated that ‘we are not that fine’. Calling the case numbers Covas mentioned, Kallas said, “I could not understand the numbers.”
Sinovac did not respond Science‘s request for more information. But Kallas says the root of the disagreement between Butantan and Sinovac is a confirmed case of COVID-19, as definitions may differ. The greater the number and severity of symptoms that a subject has to count as a case, the higher the effectiveness of a vaccine seems. The Brazilian team and the vaccine manufacturer were at odds over whether a case should show one or two recognized COVID-19 symptoms, in addition to a positive PCR test for the virus.
Researchers who have tested CoronaVac in Turkey have apparently not been able to face such obstacles. On December 24, they unveiled preliminary data showing 26 COVID-19 cases out of 570 participants who received the placebo, and 3 cases in the 752 volunteers who were vaccinated. This translates to 91.25% efficiency and no serious security issues have arisen. The next analysis will take place in 40 cases, said Murat Akova, a researcher at Hacettepe University. Asked about the restrictions on Brazilian researchers, Akova said that “there is no such contract with Sinovac for the release of data.”
The CoronaVac trial came under fire from Brazilian President Jair Bolsonaro, who has a strong prejudice against China and the vaccine itself and is a political rival of the governor of the state of São Paulo. But Sinovac, who has negotiated with the governor of São Paulo, will send Brazil enough vaccine for 46 million doses. (Two doses are needed for full protection.) Butantan has also started making the vaccine itself, hoping to produce about 1 million doses per day. Covas says the institute has begun negotiations with several Latin American countries that want to obtain the vaccine.
Kallas, who has performed about 15 clinical trials with different vaccines, says he has never seen more aggressive attempts to control data release, fearing it would undermine an extremely positive message. “If you can prevent someone with a doctor from seeing 78% and prevent hospital admissions by 100%, let’s give a toast and celebrate it,” he says.