Chinese top respiratory expert Zhong Nanshan said on Thursday that China, in theory, has built a certain level of herd immunity, as over 83 percent of the country's population has been vaccinated.

He made the remarks at a forum of Zhong Nanshan Youth Science and Technology Innovation Award in Guangzhou City, south China's Guangdong Province, calling for more Chinese residents to take booster shots.

China began its vaccination program starting with high-risk groups in December, 2020. According to data released by the National Health Commission, over 1.2 billion people on the Chinese mainland had been fully vaccinated as of December 28, 2021, accounting for more than 85.6 percent of the country's population.

In this case, Zhong pointed out that, theoretically speaking, China's herd immunity goal has been achieved.

Furthermore, Zhong mentioned that China now has the lowest COVID-19 mortality rate in the world, with a prevalence rate of 9.4 per 100,000 and a mortality rate of 0.4 per 100,000.