China must respond promptly to the sporadic outbreaks of Omicron and must "run faster" than its spread, said a leading health expert.

Liang Wannian, head of the National Health Commission's virus control expert panel, said on Friday that Omicron is characterized by its fast, low-detectable transmission so it poses bigger challenge to mega cities on the Chinese mainland.

The highly contagious strain has become a tough test to authorities in terms of citywide response measures, nucleic acid test, and medical services, he said at a news conference organized by the State Council Information Office.

"We must upgrade our countermeasures against the virus. The most critical principle is that we must act more promptly and effectively. We must run faster than the virus," Liang told reporters when responding to a question about what lessons Beijing could draw from Shanghai's anti-Omicron measures.

"We also need to establish confidence. As a matter of fact, many Chinese cities such as Shenzhen, Changchun, Jilin and Tianjin have faced Omicron's attack. But their experiences have proved that we can achieve the goal of dynamic clearance and effectively control the outbreak," Liang said.

"We must be confident that we have the capability and conditions to beat the epidemic," he said, adding that there have been improvements in control measures in Shanghai and Beijing.

Liang noted that the elderly population is the most susceptible to Omicron, and there are a lot of elderly people in Shanghai and Beijing. Therefore, it is essential for elderly people to get vaccinated and boosted, he said.

Liang also stressed that the fight against the pandemic requires the mobilization and participation of all in the society..

"We are fighting a 'people's war' against COVID-19, and we must act faster with effective measures," he said.

Liang also said the large populations and necessary personnel mobilities in mega cities like Shanghai and Beijing have made some control measures more difficult in implementation compared with smaller cities.