China has administered 200 million COVID-19 vaccine doses as of April 21, China's National Health Commission (NHC) said at a press conference, adding that more than 80 percent of the country's health workers have been vaccinated.

Shao Yiming, chief expert at the Chinese Center for Disease Control and Prevention, said the drive to vaccinate the masses is an essential tool in establishing herd immunity.

"Getting people vaccinated is a more effective measure to block the transmission of a disease … If people don't get the jabs simply because they're not 100 percent effective, then the immune barrier cannot be established and herd immunity cannot be achieved," he said.

Shao said if everyone gets vaccinated, the possibility of a serious outbreak is much lower, despite the possibility of sporadic outbreaks.

He added that large-scale inoculations will slow the emergence of more virus variants and also buy time for research institutions to respond to the emergence of any future mutations.

Data from the NHC shows the Chinese mainland recorded 21 new COVID-19 cases on April 20, two from Southwest China's Yunnan province and 19 from overseas.

Confirmed cases worldwide have been rising for eight consecutive weeks. In last week alone, there were 5.26 million new cases - the highest weekly rise since the onset of the outbreak.