Sinovac Biotech Ltd.'s coronavirus vaccine cut in half the risk of developing symptomatic Covid-19 in a key Brazilian study, suggesting two doses of the shot is less potent than some other immunizations designed to tame the ongoing pandemic.
The study, which was posted online and hasn't yet been reviewed by independent scientists, showed the vaccine was more effective at protecting against dangerous infections. None of those who received the CoronaVac injection developed severe disease.
The results of the trial involving 9,823 volunteers bolstered similar findings from a larger Brazilian study released last week that found a 50% protection rate 14 days after the first dose. The efficacy falls short of the results with mRNA vaccines from companies including Pfizer Inc., BioNTech SE and Moderna Inc., which have been shown to prevent about 94% of infections.
The lower efficacy may be one reason some Chinese officials have floated the idea that the country's vaccines may need to be given in combination with other shots.
Gao Fu, the director of China's disease control center, said steps such as changing the amount of vaccine given, the amount of time between doses or the type of shot administered were all possible ways to boost the vaccines' potency, according to the New York Times. He subsequently told the Global Times newspaper that his comments were misunderstood, and that increasing vaccine effectiveness is a universal challenge, the Times wrote.
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