China had detected 24 imported cases of the new Omicron variant CH.1.1 and its offshoots as of Monday. However, the strain is not expected to spark widespread transmission in the short term, according to the Chinese Center for Disease Control and Prevention.

No domestic cases of the strain have been reported so far, China CDC said in a statement released on Tuesday.

CH.1.1 is a descendant of BA.2.75, an Omicron subvariant that was first reported in India in July. It is now responsible for about 25 percent of infections in the United Kingdom and has also spread quickly in Denmark and Singapore.

The variant features multiple mutations that enhance its ability to evade immunity, including a mutation seen in the more deadly Delta variant. However, there is no evidence pointing to stronger pathogenicity.

The majority of people in China have high levels of neutralizing antibodies that can protect them against CH.1.1, China CDC said.

"In the short term, CH.1.1 will not trigger large-scale outbreaks," it said, adding that people age 65 and older, those with preexisting illnesses and unvaccinated people should maintain personal protection.

China is nearing the end of the current outbreak, with BF.7 and BA.5.2 remaining the dominant strains, health officials said recently.

Zeng Guang, former chief epidemiologist at China CDC, said the nation has established basic herd immunity against COVID-19.

In an interview with People's Daily on Wednesday, he said 80 to 90 percent of people in China have acquired immunity from recent infections. That figure, coupled with vaccination coverage hitting 90 percent, means that herd immunity has been established in a basic form.

"In the short term, the epidemic situation is safe, and the thunderstorms have passed," he said.

In the long run, many uncertainties remain, such as the threat from emerging imported strains and the risk facing unvaccinated elderly people, Zeng said.

By Jan 20, the Chinese mainland had administered nearly 3.5 billion doses of vaccines and fully vaccinated 90.5 percent of its total population, official data shows.

Wang Quanyi, deputy director of the Beijing Center for Disease Prevention and Control, said on Tuesday that the Chinese capital has built temporary herd immunity and the risk of another COVID wave in the next three months is small.

He suggested that unvaccinated people age 80 and above seize the window of opportunity and get inoculated.