A professor of respiratory medicine said on Sunday that the prospects for Hong Kong's coronavirus situation depend greatly on the spread of Omicron sub-variant BA.5

David Hui, who also advises the government on coronavirus strategy, noted that the more infectious strain was being detected in 10 per cent of Covid cases – a quick jump from between one and two per cent last week.

"I think it's unlikely for the cases to come down because the reproduction number is over 1.2. Therefore, the infection figures will slowly increase," he said.

"Whether it will rise even further depends on whether the Omicron sub-variant BA.5 would become the dominant strain."

He cited Singapore as an example, saying infections surged as the sub-variant was found in more than one-third of its Covid cases.

He said as antibody levels in the vaccinated population dropped, younger people would also be advised to get a fourth jab in the months to come.