Brazil on Monday canceled a late-stage trial of a Chinese vaccine that was seen as the global frontrunner in the race to develop a protective shot for the coronavirus after a "serious side effect" from a participant.
The decision sparked a political firestorm on Tuesday after President Jair Bolsonaro, who criticized China and disapproved of his CoronaVac vaccine, called the suspension a political victory.
Instituto Butantan, the Brazilian institute involved in the CoronaVac study, called the suspension unjustified, arguing that it was triggered by the death of a study participant, but that the death had nothing to do with the vaccine.
A police report received from the New York Times said that the participant's death on October 29 was being investigated as a suicide. A senior São Paulo state government official who heads the Instituto Butantan said that fact led health experts at the institute to conclude that it had not raised red flags regarding the safety of the vaccine.
The largest state in Brazil in São Paulo is led by Governor João Doria, a political rival of Mr Bolsonaro, who has criticized the president's careless handling of the pandemic.
Gustavo Mendes, director of medicines at Anvisa, Brazil's health authority, said in an interview on Tuesday that regulators have not yet concluded that the volunteer's death was not related to the vaccine.
"It was a precaution," he said. "Unfortunately it is being politicized." He added, "A regulator is expected to hold a study until more information is available."
CoronaVac, being developed by Chinese company Sinovac, is one of 11 experimental vaccines manufactured by some of the world's leading pharmaceutical companies currently in phase 3 trials. As the world grapples with another great wave of coronavirus infections, the race to find a vaccine has intensified and made all the more competitive by fragmented geopolitics.
On the same day that Brazil suspended the Sinovac study, American company Pfizer announced that an early analysis of its coronavirus vaccine studies found that its drug was more than 90 percent effective at preventing the virus that causes Covid-19 .
Sinovac's drug was seen as the leading candidate in China. In Beijing's quest to be the first to introduce a Chinese vaccine on the world market, officials have expanded the definition of "emergency". They have allowed tens of thousands of people to receive the Sinovac vaccine and two other locally made vaccines, even though they haven't completed Phase 3 trials.
Side effects are not uncommon in phase 3 studies. AstraZeneca and Johnson & Johnson both halted their attempts after several volunteers fell seriously ill and resumed them six weeks later, in October, after they concluded the diseases were unrelated to the vaccines.
In a statement released Tuesday, Sinovac said the Instituto Butantan saw the "serious incident" as unrelated to the vaccine. The company said it was "confident in the safety" of its vaccine.
The Chinese vaccine study has sparked a political rivalry between Mr Bolsonaro and Mr Doria, who are widely expected to run for president in 2022. If the vaccine is approved, the institute will manufacture it.
Mr Bolsonaro had previously expressed skepticism about the Chinese vaccine and was happy about the setback in a message on Facebook on Tuesday.
"This is the vaccine that Doria wanted everyone in São Paulo to take," the president wrote. "Another win for Bolsonaro."
Last month, Mr Bolsonaro reacted angrily when he learned that the Ministry of Health was planning to buy 46 million doses of the vaccine.
"I ordered it to be canceled," he said. "It seems that no country in the world is interested in this Chinese vaccine."
Mr Doria's party, Brazil’s Social Democratic Party, said in a statement that the race to develop a vaccine is "not a political competition and cannot be treated like one".
It accused Mr Bolsonaro of "putting his political aspirations above all else and disregarding the lives of Brazilians".
It is rare for a drug that has not been fully tested to be administered so frequently, and scientists from around the world have repeatedly warned that the Chinese government is putting the health of its population at risk before completing any late-stage studies.
Sinovac previously said that more than 10,000 people in Beijing had been injected with his vaccine. Regardless of this, it was said that almost all employees – around 3,000 in total – and their families had taken over. Vaccine experts said it was important to complete the third and final phase of human testing before the drug was made available. Phase 3 studies affect tens of thousands of people and can detect unusual 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 approximately 27,000 people. Sinovac said it was hoping to complete the trials by the end of the year, but suspending the trial in Brazil could affect the process in other countries and potentially derail that schedule.
Indonesian state-owned pharmaceutical company Bio Farma, which is conducting trials for Sinovac, said it has no plans to abandon its trials, said Iin Susanti, head of Bio Farma's business planning and strategy department.
The suspended Brazilian trial is a reminder of the daunting challenges Chinese vaccine companies face when they go overseas. Few companies have experience abroad, let alone in potential political minefields. All had to test their vaccines in locations with active outbreaks as the virus had been largely eradicated in China.
In Brazil, the trials have been politically charged as supporters of Mr Bolsonaro, who downplayed the threat and blamed China for the pandemic, criticized them.
Prof. Raina MacIntyre, director of the biosecurity program at the Kirby Institute, University of New South Wales in Sydney, Australia, said serious side effects in a vaccine study were "extremely rare" but added, "We can expect this scenario to happen again with different vaccines . If you have 45,000 people in a study, it is very likely that one person will have a serious health event during that time. "
Professor MacIntyre said the hiatus would allow a security oversight committee to investigate.
Vaccine experts said they saw data from Sinovac's early-stage studies as showing promise. The results of the company's Phase 1 studies showed no adverse effects, and Phase 2 studies showed 90 percent protection against SARS-CoV-2, the virus that causes Covid-19.
Watching a Chinese company first develop a vaccine was a priority for President Xi Jinping. Mr. Xi has put his personal reputation on efforts in what is seen as a way to clear some of the blame several countries placed on China for its initial missteps when the virus first emerged in Wuhan city last year .
Sinovac treatment is an inactivated vaccine, which means it consists of a coronavirus that has either been weakened or has been killed by chemicals.
Tao Lina, a vaccine expert in Shanghai, said he believed the Brazilian suspension was based not on science but on politics.
"Inactivated vaccine technology is very mature and the possibility that this incident is vaccine-related is very slim," said Tao, a former immunologist at the Shanghai Centers for Disease Control and Prevention. He said the Chinese government is unlikely to stop the emergency program because "it will cause a lot of panic".
Reporting was contributed by Manuela Andreoni, Letícia Casado, Elsie Chen and Muktita Suhartono. Amber Wang contributed to the research.