Chinese COVID-19 Vaccine Shows 50.4 Percent Efficacy in Brazil Trial

A technician works in a lab at Sinovac Biotech, where the company is producing its potential COVID-19 vaccine CoronaVac, during a media tour in Beijing on Sept. 24, 2020. (Kevin Frayer/Getty Images)

A leading Chinese COVID-19 vaccine candidate has been found to be 50.4 percent effective, according to the results of a late-stage trial in Brazil, a potential setback to the Chinese regime as it seeks to leverage the vaccine to boost its global image.

The results from Brazil’s state-funded Butantan Institute on Jan. 12 were just enough to pass the 50 percent threshold set by the World Health Organization for regulatory approval. It was far lower than initial claims announced last week that touted a 78 percent efficacy rate.

CoronaVac, a vaccine developed by Beijing-based drugmaker Sinovac Biotech, is one of Brazil’s two immunization candidates. The government last week made a deal to purchase up to 100 million doses of the Chinese vaccine.

The latest revelation has fueled skepticism about Chinese vaccines. Brazilian President Jair Bolsonaro, who in October vowed that “Brazilian people will not be anyone's guinea pig,” said on Jan. 13 that he was right to question the credibility of vaccines from China.

"This 50 percent is good, is it? All the [criticism] I got for my comments, and now they are seeing the truth. Four months of being lambasted because of the vaccine," Bolsonaro told supporters outside his residence.

Bolsonaro noted that he had no say in vaccine approval, as the health regulator Anvisa would make the final call.

Last week, Butantan Institute researchers celebrated a 78 percent efficacy rate of the CoronaVac vaccine against “mild-to-severe” virus cases, and 100 percent rate for very severe cases. The figure fell after accounting for a group of “very mild” cases among over 12,000 volunteers who didn't require clinical assistance, the institute said on Jan. 12.

Chinese state media made light of the trial results in the news coverage. A Jan. 13 headline from the state-affiliated tabloid Global Times emphasized that the Sinovac vaccine was “100% effective in preventing severe cases, could reduce hospitalizations by 80%,” citing a Chinese doctor who claimed the vaccine is “good enough.” The Party-run Beijing Daily attached importance to the “safety” and “effectiveness” of the vaccine, without mentioning the numbers.

Syringes of the potential COVID-19 vaccine CoronaVac are seen on a table at Sinovac Biotech at a press conference in Beijing on Sept. 24, 2020. (Kevin Frayer/Getty Images)

In the United States, vaccines developed by Pfizer and Moderna, both with about a 95 percent effectiveness, received FDA authorization in December and have began to be administered to the general public.

In China, authorities have rushed to vaccinate people since July under an emergency use policy that allowed the use of vaccines that hadn’t completed clinical trials.

Yin Weidong, chairman of Sinovac Biotech, said in a Jan. 13 news conference that the company plans to double its production capacity to 1 billion doses by February. The Jan. 12 efficacy results have so far been the lowest for the vaccine. The company has also received orders from Turkey and Indonesia for CoronaVac, with interim data showing an efficacy rate of 91.25 percent and 65.3 percent respectively.

Asked about concerns around the vaccine, Yin said the phase 3 trials from Brazil and elsewhere “have been sufficient to prove the safety and effectiveness of the CoronaVac vaccine around the world.”

In a move to assure the public, Hong Kong, which has already placed orders for Sinovac vaccines, said on Jan. 13 that it would have a panel of experts review any vaccine based on clinical data before its rollout.

The Butantan Institute has faced criticism for transparency over CoronaVac trial data. It was initially scheduled to release the vaccine testing results in mid-December, but delayed the action multiple times, citing a need for Sinovac to collect additional data.