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Brazil said on Monday it had halted an advanced trial of a Chinese vaccine, which had been seen as a world leader in the race to develop a protective vaccine against the coronavirus, after a “serious adverse” reaction in a participant.
Brazil’s health regulator has provided little information on its decision, including whether the reaction was related to the vaccine, called CoronaVac and produced by Chinese company Sinovac, or by chance.
The participant who had the reaction fell ill on October 29, authorities said. They did not disclose where in Brazil the vaccine was administered or what happened to the volunteer, citing patient confidentiality. In a statement, they said such a “serious adverse event” could include death, disability, hospitalization, birth defects or other “clinically significant events”.
CoronaVac is one of 11 investigational vaccines, produced by some of the world’s largest pharmaceutical companies, currently in Phase 3. As the world braces for another major wave of coronavirus infections, the race for a vaccine has turned. intensified and was made all the more competitive by turbulent geopolitics. On the same day that Brazil suspended the Sinovac trial, U.S. company Pfizer announced that an early analysis of its coronavirus vaccine trials suggested that its drug was over 90% effective in preventing the virus responsible for the Covid-19.
Sinovac’s drug was seen in China as a top candidate. But in Beijing’s effort to have a Chinese vaccine the first to hit the global market, officials have broadened the definition of “emergency use.” They have enabled tens of thousands of people to receive the Sinovac vaccine and two other locally made vaccines, although they have not yet concluded phase 3 trials.
Adverse effects are not unusual in phase III trials. AstraZeneca and Johnson & Johnson both halted their trials after several volunteers fell seriously ill, resuming them six weeks later, in October, after concluding the illnesses were unrelated to vaccines.
Details of why Brazil’s health regulator suspended trials were uncertain.
In a statement on Tuesday, Sinovac said Instituto Butantan, the medical center that coordinates the Brazilian trials, said the “serious event” was unrelated to the vaccine. The company said it was “confident in the safety” of its vaccine.
According to reports, the institute confirmed that a volunteer had died, but local officials said they were “surprised” by the government’s decision to stop the trials.
Dimas Covas, director of the institute, told a Brazilian television station that he found the government regulator’s decision strange “because it is a death unrelated to the vaccine”.
Professor Kim Mulholland, a pediatrician at the Murdoch Children’s Research Institute in Melbourne, Australia, called it “alarming” that Instituto Butantan does not seem to know why the trial was stopped. “It leaves me wondering who did this and why,” added Prof Mulholland. “This is the question that really needs to be answered because it is a violation of the normal process.”
It is rare for a drug that has not been fully tested to be administered so widely, and scientists around the world have repeatedly warned that the Chinese government is risking the health of its people before late-stage trials are completed.
Sinovac previously said more than 10,000 people in Beijing had received an injection of its vaccine. Separately, he said almost all of his employees – around 3,000 in total – and their families took him. Vaccine experts said it was important to conclude the third and final phase of human testing before making the drug available. Phase 3 trials involve tens of thousands of people and can detect rare but potentially serious side effects.
The company began phase 3 trials in Brazil and Indonesia in August, and Turkey in September, testing its vaccine on around 27,000 people. Sinovac has said he hopes to complete the trials by the end of the year, but the suspension of the trial in Brazil could affect the process in other countries, which could derail that timeline.
Indonesian state-owned pharmaceutical company Bio Farma, which is conducting trials for Sinovac, said it has no plans to cancel trials, according to Iin Susanti, head of Bio Farma’s planning and business strategy division. .
The suspended Brazilian trial is a reminder of the formidable challenges Chinese vaccine companies face when they go overseas. Few companies have experience in overseas operations, let alone navigating potential political minefields. All had to test their vaccines in places where epidemics were active because the virus had been largely eradicated in China.
In Brazil, the trials were politically tense as supporters of President Jair Bolsonaro, who downplayed the threat and blamed China for the pandemic, criticized them.
The trials had mainly taken place in São Paulo, the country’s most populous state, supported by its governor, João Doria, a rival of Mr. Bolsonaro. Last month, Bolsonaro contradicted his own health minister and rejected the announced purchase of 46 million doses of the Sinovac vaccine, saying, “The Brazilian people will not be anyone’s guinea pig.
Professor Raina MacIntyre, who heads the biosafety program at the Kirby Institute at the University of New South Wales in Sydney, Australia, said serious side effects from a vaccine trial were “extremely rare,” but added : “We can expect to see this scenario repeat itself with different vaccines. If you have 45,000 people in a trial, it is highly likely that someone will suffer from a serious health problem during that time. “
Professor MacIntyre said the hiatus would allow a safety oversight committee to examine whether the vaccine caused the disease.
The length of the suspension is unclear. Professor MacIntyre said if the event happened in a volunteer who was given a placebo, it could take a few days. But if not, it could take weeks or even months.
Vaccine experts said they saw data from Sinovac’s preliminary trials as promising. Results from the company’s Phase 1 trials showed no adverse effects, and Phase 2 trials showed 90% protection against SARS-CoV-2, the virus responsible for Covid-19.
Seeing a Chinese company develop a vaccine first has been a priority for the country’s leader, Xi Jinping. Xi has staked his personal reputation on the effort, which is seen as a way to erase some of the blame several countries blamed on China for its initial missteps when the virus first emerged in the country. Wuhan city last year.
The treatment for Sinovac is an inactivated vaccine, which means it is made up of a coronavirus that has been weakened or killed by chemicals.
Tao Lina, a vaccine expert in Shanghai, said he believed the Brazilian suspension was not based on science but on policy.
“The technology of inactivated vaccines is very mature and the possibility that this incident is related to vaccines is very slim,” said Mr. Tao, a former immunologist at the Shanghai Center for Disease Control and Prevention. He said the Chinese government was unlikely to stop the emergency use program because “it will cause a lot of panic.”
Elsie Chen and Muktita Suhartono contributed reporting. Amber Wang contributed to the research.
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