A medical worker inoculates a citizen with a booster shot of COVID-19 vaccine at a vaccination clinic in Fanyu District of Guangzhou City, south China's Guangdong Province, Oct. 18, 2021. (Xinhua/Deng Hua)

BEIJING, Oct. 27 (Xinhua) -- More than 2.251 billion doses of COVID-19 vaccines had been administered on the Chinese mainland as of Tuesday, data from the National Health Commission showed Wednesday.