Hong Kong recorded 47 serious flu infections – including 20 deaths – last week, with another 17 related fatalities logged within four days from Sunday as a leading expert appealed to the public to get vaccinated against the disease.

Professor Lau Yu-lung, from the University of Hong Kong, on Thursday warned that years of wearing masks and handwashing to protect against Covid-19 had also weakened people’s immunity and left the elderly and the young especially vulnerable.

“Most [of the serious cases] are children and the elderly,” said Lau, who chairs the Scientific Committee on Vaccine Preventable Diseases. “The elderly have weaker immunity and organs, and they usually have chronic illnesses.”