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Concern is mounting that China's coronavirus vaccines are less effective at quelling the disease, raising questions about nations from Brazil to Hungary that are depending on the shots and the country's own mammoth inoculation drive.
While vaccines developed by Pfizer Inc., Moderna Inc. and even Russia's Sputnik shot have delivered protection rates of more than 90%, Chinese candidates have generally reported much lower efficacy results. Research released Sunday showed the rate for Sinovac Biotech Ltd.'s vaccine — deployed in Indonesia and Brazil — was just above 50%, barely meeting the minimum protection required for coronavirus vaccines by leading global drug regulators. The other Chinese shots have reported efficacy rates of between 66% to 79%.