A new study led by Chinese epidemiologist Zhong Nanshan found that Chinese COVID-19 vaccines curbed the spread of the extra-contagious Delta variant during the May outbreak in Guangzhou.
Researchers from the Guangzhou Center for Disease Control and Prevention learned that two shots of China-developed inactivated vaccines provided a 59% efficacy rate against the Delta strain of COVID-19.
The double dose also had an efficacy of 70.2% against moderate cases and 100% against severe cases.
Xinhua reported that a single-dose vaccination, with an efficacy of 13.8%, was not enough protection for the Delta strain, citing the study.
The World Health Organization describes vaccine efficacy as follows:
“A vaccine’s efficacy is measured in a controlled clinical trial and is based on how many people who got vaccinated developed the ‘outcome of interest’ (usually disease) compared with how many people who got the placebo (dummy vaccine) developed the same outcome.”
The researchers in the study noted the Guangzhou outbreak provided a real-world setting to determine the effectiveness of the inactivated vaccines against the Delta strain. Prior to that, it wasn’t clear how well the vaccine would hold up against the recent variant of COVID-19.
The study involved 628 participants – 153 confirmed COVID-19 cases from the Delta strain and 475 close contacts.
The majority of vaccinated cases had received two doses of the vaccine developed by Sinovac, while over a quarter of cases accepted two shots of the Sinopharm vaccine.
Both vaccines have been granted emergency use by the WHO.
Unlike the most recent outbreak in Jiangsu in late July, the May outbreak in Guangzhou was largely contained in one district. Within a month, the spread of COVID-19 was under control, and the city reopened dine-in service.
Guangzhou conducted more than 16 million nucleic acid tests over the course of the month. One man in Guangzhou’s Conghua district attacked an officer with a fork after refusing to take a COVID-19 test.
The deputy director of the Guangzhou municipal public security bureau later said that non-cooperative behavior regarding COVID-19 prevention measures could be considered a criminal offense.
[Cover image via That’s]