On the same day that Pfizer and BioNTech released blockbuster results from the Phase III trial of their COVID-19 vaccine, Brazil threw a wrench into the plans of one of China’s most promising coronavirus vaccine candidates.
Brazilian health regulator Anvisa announced on Monday that it had suspended the Phase III clinical trial of a COVID-19 vaccine made by Sinovac, a Chinese pharmaceutical company. Anvisa said it had discovered that a participant in Sinovac’s trial had experienced a “severe adverse event” and that Sinovac’s trial would be delayed as it investigated the case. Anvisa did not provide additional details about the patient and did not explain why it announced the suspension more than a week after it became aware of the problem.
A spokesman for Sinovac told Fortune that after communicating with the Butantan Institute, its partner in Brazil, Sinovac does not believe the “serious adverse event” was related to its vaccine. “We are confident in the safety of the vaccine,” the spokesman said.
On Monday night, Dimas Covas, the director of the Butantan Institute, suggested that he disagreed with the government’s decision to suspend the trials. He said that a volunteer in the trials had died but not because of Sinovac’s vaccine.
“We found this Anvisa decision strange, because it is unrelated to the vaccine,” Covas told a Brazilian news channel.
The Monday announcement by Anvisa marks the first time a Chinese vaccine maker has been forced to delay the trial of a COVID-19 vaccine. Other COVID-19 vaccine makers have had to pause their Phase III trials because of unexplained health issues among participants. British pharmaceutical firm AstraZeneca and U.S. drug giant Johnson & Johnson experienced trial delays, but both companies have since resumed the tests.
But unlike AstraZeneca and Johnson & Johnson, Sinovac has already inoculated tens of thousands of people outside of clinical trials through China’s controversial emergency use program. Sinovac’s trial delay raises the prospect that China has been inoculating its citizens with a potentially unsafe vaccine and showcases the dangers of attempting to bulldoze traditional vaccine approval processes.
Process perils
Chinese vaccine makers either lead, or are involved in, five of the 11 vaccine efforts that have reached Phase III trials. Combined, they’re testing their candidates in hundreds of thousands of volunteers in over a dozen countries around the world.
Phase III trials are designed to evaluate a vaccine’s effectiveness and safety on a large scale. Each trial requires tens of thousands of volunteers so there’s a better likelihood of turning up rare side effects.
But beyond standard vaccine testing, at least three Chinese vaccine makers are involved in China’s emergency use vaccine program, which has allowed participating vaccine makers to inoculate hundreds of thousands of Chinese citizens—if not more—outside the bounds of clinical trials and before the candidates are proven safe and effective.
China’s government has not disclosed how many COVID-19 vaccine doses it has distributed through the emergency use program, but vaccine makers and local governments have released some limited data. State-owned vaccine maker Sinopharm reportedly distributed over 480,000 doses of its candidate in China as of mid-October; that total may include doses that were part of a clinical trial. China’s eastern Zhejiang province, meanwhile, also said in October that it had administered 743,000 flu and coronavirus shots in 2020 without providing further details on how many of the shots were for COVID-19 or which COVID-19 vaccine candidate it used.
In August, China allowed Sinovac to distribute the CoronaVac candidate to frontline medical workers, government employees, and other essential workers in China through the emergency use program.
By September, the company confirmed that it had inoculated tens of thousands of people through the program, including 3,000 company employees, plus their families.
News reports indicate that Sinovac may already be widely distributing its vaccine across China. In October, Jiaxing, a city in eastern China, announced that it was selling the Sinovac vaccine to government workers and high-risk residents for roughly $60.
If the Brazil investigation reveals that Sinovac’s vaccine is potentially unsafe, the tens of thousands of people who have received the vaccine may have been put at unnecessary risk. Such risks are why scientists have been skeptical of China’s emergency use program for COVID-19 vaccines from the start.
“Claims of having a vaccine ready to distribute before you do testing, I think, is problematic, at best,” Anthony Fauci, director of the U.S.’s National Institute of Allergy and Infectious Diseases, said in July.
Brazil’s Butantan Institute, a scientific research center that is partnering with Sinovac on the vaccine trials, said it will hold a press conference about the trial suspension on Tuesday morning in Brazil.
Battles in Brazil
Even before the trial pause, Sinovac COVID-19 vaccine candidate had become a flashpoint in Brazil.
The Butantan Institute and Sinovac started enrolling 9,000 Brazilian volunteers in Phase III trials in July. In late September, Brazil’s São Paulo state purchased 46 million doses of CoronaVac for $90 million and asked Brazilian health authorities to register the candidate for potential distribution.
In October, João Doria, governor of São Paulo, said CoronaVac was the “safest” and “most promising” of all the vaccine candidates tested in the country. (Brazil has also hosted Phase III trials for Pfizer and BioNTech’s vaccine candidate.)
Brazilian President Jair Bolsonaro took issue with Doria’s remarks and said Brazil would not purchase Sinovac’s or any other Chinese vaccine because of the country of “origin.” Even so, later in October, Brazilian authorities approved the import of 6 million doses of Sinovac’s vaccine candidate.
Before news of Sinovac’s trial delay, Doria announced on Monday that São Paulo is building a facility to produce 100 million doses of Sinovac’s candidate.
