The third time, is it the charm? Brazil Reduces Efficacy Claims of COVID-19 Vaccine From China | Science

By Jon Cohen, Sofia MoutinhoJan. 12, 2021 at 5:50 p.m.

Science‘s COVID-19 reporting is supported by the Pulitzer Center and the Heising-Simons Foundation.

In the third in a series of conflicting announcements regarding a Chinese-made COVID-19 vaccine candidate, Brazilian researchers reported today that the results of their efficacy trial were less impressive than they claimed last week. When analyzed under stricter criteria than those used previously, the vaccine’s efficacy against all forms of COVID-19, including mild cases, dropped from around 78% to 50%.

The vaccine still appeared to offer nearly 100% protection against disease severe enough to require hospitalization, although the trial collected too few of these cases for this finding to reach statistical significance. Commenting during today’s press conference, microbiologist Natália Pasternak Taschner, president of the Question of Science Institute, a Brazilian nonprofit that aims to support public policy based on scientific evidence, said that it was a “clean and clear study” and stressed that she wanted vaccine for herself and her parents. “We don’t need to say it’s the best vaccine in the world,” said Pasternak, who was not in the trial. “We have to say this is our vaccine and it is a good vaccine to start the process of controlling the pandemic.”

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The vaccine, made by Sinovac Biotech in China, contains a chemically inactivated version of SARS-CoV-2, the virus responsible for COVID-19. At last week’s press conference that announced the 78% efficacy, Dimas Tadeu Covas, director of the Butantan Institute – a public vaccinator in São Paulo who is conducting the study with Sinovac – gave few details. (The information was even more sketchy at a press conference last month, when the team only claimed the efficiency was over 50%.) But when pressed by reporters, he replied that this number came from about 220 cases of symptomatic disease. Today, researchers revealed that the 78% figure was actually from analysis of COVID-19 cases in which people sought help for symptoms and tested positive for the virus – 31 cases among the placebo recipients in the trial and seven in the vaccinated group.

A more detailed analysis including trial participants who tested positive but had symptoms so mild that they did not seek help found 167 cases of COVID-19 in the placebo group and 85 in people who received the vaccine, for an estimated efficacy of 50.34%. Even taking into account the statistical uncertainties, this is considerably below the efficiencies above 90% of three other COVID-19 vaccines already authorized.

But Esper Kallas, an investigator based at the main campus of the University of São Paulo who spoke at the press conference, notes that, since the definitions of a positive case vary from trial to trial. ‘other,’ there may not be precise comparability between studies. In the trial in Brazil, the liberal definition of a case “tested it most difficult,” said Ricardo Palácios de Butantan, who was the clinical director of the study. “It’s like comparing someone who runs a mile on cobblestone ground to someone who runs a mile with obstacles.”

Guidelines from the World Health Organization and those from several countries indicate that a COVID-19 vaccine that is 50% effective with a lower limit of 30% meets the standards for initial authorization. “It has all the requirements to justify its emergency use,” Covas said. Brazil has one of the most devastating COVID-19 outbreaks in the world, and Covas and several other speakers at the press conference said they hope the Sinovac vaccine – which Butantan is currently producing – will be widely used quickly. . No vaccine has yet received approval in Brazil, but regulators are also reviewing efficacy data in a vaccine manufactured by AstraZeneca and the University of Oxford.

Covas said the release of the new Chinese vaccine data shows “our full commitment and transparency in this process.” Previously, Sinovac had asked Butantan not to disclose details of the study so that the company could analyze the data more closely, which led to claims that the Brazilian researchers had been muzzled by the company. Sinovac did not respond to repeated requests for comment from Science.

Kallas notes that the current case analysis only lasts November 28, 2020 and that “much more” data is now available. Efficacy trials of the Sinovac COVID-19 vaccine are also underway in Turkey and Indonesia and have presented even more preliminary data. Researchers in Turkey reported on Dec. 24 that they found 91.5% effectiveness with its first 29 cases, and Indonesia reported 65% effectiveness with 25 cases. Indonesia gave permission for emergency use of the vaccine yesterday.

Epidemiologist Ethel Maciel of the Federal University of Espírito Santo said the choice to publish vaccine data at different press conferences with vague figures was detrimental. “People started to be suspicious and were left with a lot of doubts which encouraged public distrust of vaccines,” says Maciel, who works on the federal immunization plan.

“We need to reduce moderate and severe cases more than ever, and to that end, the vaccine is very good,” she says. “But we will need a lot of people vaccinated to reduce transmission.”