The coronavirus vaccine developed by China’s Sinovac Biotech has been found to be 50.4 percent effective in a late-stage Brazilian trial—falling far below the 78 percent level that was initially announced.
While the percentage barely met the 50-percent threshold required for regulatory approval, the finding has only raised more concerns about the veracity of vaccine data put forth by Chinese companies.
Last week, the state-run Butantan Institute stated that Sinovac’s CoronaVac vaccine was nearly 80 percent effective among volunteers with mild to severe COVID-19 infections, but that plunged by twenty-eight percentage points when including “very mild” cases that didn’t require medical assistance or hospitalization.
Phase three trials of the vaccine involved thirteen thousand healthcare workers across eight Brazilian states.
“The Butantan Institute and the government of Sao Paulo report that the coronavirus vaccine achieved a 50.38 percent overall efficacy rate in the clinical study conducted in Brazil, in addition to (an efficacy rate of) 78 percent for mild cases and 100 percent for moderate and severe cases of COVID-19. All rates are higher than the 50 percent level required by the World Health Organization,” the statement released by Sao Paulo government said.
For comparison, recently approved vaccines from Pfizer-BioNTech and Moderna were found to be about 95 percent effective in their respective late-stage trials.
“Regarding the overall efficacy of the analysis, we met the requirements of the World Health Organization with 50.38 percent,” Ricardo Palacios, medical director for clinical research at the Butantan biomedical center in Sao Paulo, said Tuesday during a local news conference.
Turkey and Indonesia have also conducted their own separate trials on the CoronaVac vaccine. On Monday, Indonesia approved the vaccine for emergency use after late-stage trials revealed that it was 65.3 percent effective. Meanwhile, Turkish researchers said the vaccine was shown to be 91.25 percent effective.
Brazil and other developing countries around the world have pinned their hopes on China-developed vaccines as richer nations already have purchased most of the vaccine doses manufactured in the West.
The South American country has reported more than 8.2 million coronavirus infections and 205,000 related deaths—both figures ranking in the top three globally, according to the latest data compiled by Johns Hopkins University.
Not all of China’s vaccines, though, have shown such low efficacy levels. The United Arab Emirates recently conducted its own trial on China’s Sinopharm vaccine, which yielded an 86 percent efficacy rate, according to UAE’s national health authorities.
Unlike leading Western competitors, China’s vaccine shot relies on a long-tested technology that uses a killed virus to deliver the vaccine. The shots developed by Pfizer and its German partner BioNTech, for example, tap into newer, less-proven technology that targets the virus’ spike protein using RNA.
Ethen Kim Lieser is a Minneapolis-based Science and Tech Editor who has held posts at Google, The Korea Herald, Lincoln Journal Star, AsianWeek, and Arirang TV. Follow or contact him on LinkedIn.