Inactivated COVID-19 vaccines developed by China curbed the spread of the Delta variant during a May outbreak in Guangzhou city in south China, a study has shown.
Led by reputed Chinese epidemiologist Zhong Nanshan, researchers from the Guangzhou Center for Disease Control and Prevention found that two shots of the vaccines provided an efficacy of 59 percent against COVID-19 caused by the Delta variant, 70.2 percent against moderate form of the disease, and 100 percent against severe cases.
Meanwhile, with an efficacy of 13.8 percent, single-dose vaccination did not provide sufficient protection.
Due to effective containment of the epidemic, testing vaccine efficacy has been challenging in the Chinese mainland. A real-world setting in the study has offered an opportunity to determine the effectiveness of two existing inactivated vaccines against the Delta strain, said the researchers.
The findings have been published in the journal Emerging Microbes & Infections.