A vaccine from Sinovac from China protected health professionals in Brazil from developing severe COVID-19.
REUTERS / Thomas Peter
By Jon Cohen, Sofia Moutinho
Science‘s COVID-19 reports are supported by the Pulitzer Center and the Heising-Simons Foundation.
Brazil, with more cases of COVID-19 than any other country after the United States and India, is about to have its first vaccine authorized for the pandemic disease. In a press conference today, Brazilian researchers reported that a vaccine manufactured by the Chinese company Sinovac is safe and has 78% effectiveness in preventing mild cases of COVID-19 in a study of more than 12,000 health professionals. It also completely prevented moderate and severe illnesses caused by SARS-CoV-2 infections, the team said. “The result we are seeing today is fantastic,” said Rosana Richtmann, a doctor at the Institute of Infectious Diseases of São Paulo Emilio Ribas, at a news conference.
Dimas Tadeau Covas, head of the Butantan Institute – a state-owned vaccine manufacturer in São Paulo that co-sponsors the trial – hopes that the Brazilian regulatory agency will authorize the vaccine, called CoronaVac, for emergency use in the coming days. “We now have all the documentation to place the order,” he said. Brazil also has ongoing effectiveness tests for a COVID-19 vaccine produced by AstraZeneca and the University of Oxford and many scientists there hope it will also receive authorization soon. But the good news about CoronaVac was overshadowed by complaints that the ad included little data – and that Sinovac has gagged his Brazilian collaborators. In fact, Brazilian researchers had already given a press conference to announce that the vaccine was a success, but were not allowed to provide an exact number of efficacy.
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Most vaccines authorized in other countries depend on high-tech approaches, such as the coding of the messenger RNA for the SARS-CoV-2 surface protein, or the approach adopted by the AstraZeneca-Oxford vaccine, which uses a harmless viral vector that carries the gene for that protein. But Sinovac turned to a more established approach. His vaccine, which is also being tested for effectiveness in Turkey and Indonesia, depends on the entire coronavirus, chemically mutilated to prevent disease. The reported efficacy against mild disease is below the 95% achieved by two mRNA vaccines. But the “main objective” of COVID-19 vaccines, said Covas, is to prevent infected people from progressing to serious illnesses. A different inactivated vaccine against SARS-CoV-2, produced by Sinopharm’s China National Biotec Group, has almost identical results, the company said last week in a major efficacy trial in several countries in the Middle East.
Both Sinovac and Sinopharm have kept confidential what their partners can reveal about their vaccines. At the press conference on December 23, held in São Paulo, at the governor’s residence, the researchers said that, because of a contractual agreement with Sinovac, they could only report that CoronaVac was more than 50% effective, internationally standard accepted for emergency clearance. Today’s presentation revealed the specific effectiveness rate, but the researchers were shy in describing the exact number of people who developed the disease in the vaccinated arms and in the placebo group.
In a formal presentation of the data at Butantan today, Covas made no mention of the case numbers, stating that the data will be published in a scientific publication and for Brazilian regulatory bodies. But when pressed by journalists, he admitted that there were 218 cases of minor illnesses. “The exact number is 160 something in the placebo group and less than 60 in the vaccinated group,” he said. (That would be 63%, not 78%, effectiveness.) CoronaVac appeared to work just as well in the elderly as it did in other age groups, the researchers added.
The lack of data – not to mention the discrepancy in effectiveness – predictably led to immediate skepticism. “Until they show us these numbers, it’s nothing more than an empty ad,” tweeted epidemiologist Denise Garrett, vice president of the nonprofit Sabin Vaccine Institute.
Details were also sparse in announcements of initial efficacy trials by other vaccine manufacturers COVID-19. But a researcher who runs one of the 16 sites that conduct the CoronaVac study in Brazil, Esper Kallas, from the University of São Paulo, said that even the study’s researchers still don’t know all the data. Kallas, who spoke with Science after the press conference, he said he was “happy” with the results. “We know that 78% is true.” But he is frustrated because “we don’t have the granularity of it”. As for the case numbers mentioned by Covas, Kallas said: “I couldn’t understand those numbers.”
Sinovac did not respond to Sciencerequest for more information. But Kallas says the root of the disagreement between Butantan and Sinovac is what constitutes a confirmed case of COVID-19, as definitions may vary. The greater the number and severity of symptoms that a study subject must have to count as a case, the greater the effectiveness of the vaccine will appear. The Brazilian team and the vaccine manufacturer were at odds over whether a case should have one or two recognized symptoms of COVID-19, as well as a positive PCR test for the virus.
The researchers who tested CoronaVac in Turkey apparently did not face such obstacles. On December 24, they revealed preliminary data showing 26 cases of COVID-19 in 570 participants who received the placebo and 3 cases in the 752 vaccinated volunteers. This translated into 91.25% effectiveness and no serious security issues appeared. The next analysis will take place in 40 cases, said Murat Akova, a researcher at Hacettepe University who is helping to conduct the study. Asked about the restrictions on Brazilian researchers, Akova states that “there is no such contract with Sinovac for the release of data”.
The CoronaVac trial was criticized by President Jair Bolsonaro, who has a strong prejudice against China and the vaccine itself and is a political rival to the governor of the state of São Paulo. But Sinovac, which negotiated with the governor of São Paulo, will send Brazil enough vaccine for 46 million doses. (Two doses are needed for total protection.) Butantan has also started to manufacture the vaccine and expects to produce around 1 million doses per day. Covas says the institute has started negotiations with several Latin American countries that wish to obtain the vaccine.
Kallas, who has conducted about 15 clinical trials of different vaccines, says he has never seen more aggressive attempts to control the dissemination of data and fears it will undermine a highly positive message. “If you can prevent someone from being seen by a doctor by 78% and prevent hospitalizations by 100%, let’s toast and celebrate,” he says.