Sinovac vaccine shot’s efficacy uncertain despite Brazil, Turkey results
With trials of Sinovac Biotech Ltd.’s coronavirus vaccine in Brazil and Turkey suggesting the shot has a protection rate on either side of 90%, there is still no final assessment on exactly how effective it is in protecting people against Covid-19.
Sinovac is finalizing results of phase III trials carried out in Brazil, Turkey, Indonesia and Chile, according to a person familiar with the trials. Those tests are relatively independent from each other and conducted according to different protocols, rather than subject to unified norms that typically govern such trials, said the person, who asked not to be identified because the data isn’t public.
Researchers in Brazil earlier this week delayed releasing complete information on Sinovac’s vaccine, saying only that it was found to be more than 50% effective. Sao Paulo state Health Secretary Jean Gorinchteyn offered more specific guidance on Thursday, saying the vaccine “didn’t reach 90%” efficacy, which would make it less successful than those developed by Pfizer Inc. and Moderna Inc.
“We don’t know how much more than 50% it was, whether it was 60%, 70% or 80%, but it’s at levels that allow us to reduce the impact of the disease on our population,” Gorinchteyn said in an interview with Brazil’s CBN Radio. “We knew that the effectiveness would never reach 90%.”
Adding to the confusion, Turkey said a trial of Sinovac’s vaccine taking place in its country showed an estimated efficacy rate of 91.25%. That trial, however, is based on only 29 cases, which is considered insufficient to draw a definitive conclusion on the shot’s effectiveness, according to the person familiar with the trials. The trial will continue to collect Covid-19 cases to get a more finalized reading, the person said.
A Sinovac spokesman declined to comment on questions about the vaccine’s efficacy.
The delay in the announcement of definitive results has created confusion over the effectiveness of Sinovac’s shot. Chinese developers have been slow compared with their western peers in releasing efficacy data, risking an erosion of confidence in these candidates as the world puts a laser focus on which vaccines are most successful in fighting the pandemic.
Pfizer and Moderna’s shots, meanwhile, have been shown to reduce symptomatic cases by well over 90%.
The reason Brazil hasn’t yet disclosed complete efficacy numbers is because Sinovac and its partners are reviewing all the Covid-19 cases found among participants, the person said. The Brazil trial has yielded more than 170 cases, but Sinovac needs to verify them to see whether they all meet the criteria set out by the Chinese drug regulator.
Regulators from China and Brazil, as well as Sinovac and its partners are still in the process of analyzing data from the Brazil trial, according to the person. Ultimately, Sinovac hopes to see unified standards to ensure equal comparisons across different trial sites, the person said. The protocol for the Brazil trial says Covid-19 cases are diagnosed in line with guidance from the U.S. Food and Drug Administration.
The late-stage trial of Sinovac’s vaccine in Brazil, involving about 13,000 participants, suggested the shot is “safe and effective,” authorities at the Butantan Institute and the state of Sao Paulo said earlier in the week.
Sinovac is betting on a successful vaccine to inoculate more people around the world and save lives, especially in developing countries like Brazil that will have limited access to the Pfizer and Moderna shots. Sinovac’s shot is potentially better suited to developing countries because it can be kept at normal refrigerator temperatures, while vaccines from Pfizer and Moderna require deep-freeze conditions for storage and transportation.
The Sinovac vaccine has been at the center of a political dispute between Sao Paulo Governor Joao Doria and President Jair Bolsonaro, who says a vaccine from China can’t be trusted. Bolsonaro again cast doubt on the effectiveness of the Sinovac vaccine in a Christmas Eve address broadcast on Facebook.
“I want to make it very clear that the label of this vaccine will be ‘we are not responsible for any side effect.’ Responsibility is yours,” he said.