​A government pandemic adviser on Saturday defended a vaccine policy shift in Hong Kong requiring residents to pay for an additional Covid-19 booster shot from April 20, as he argued public resources should be prioritised for vulnerable groups.

Ivan Hung Fan-ngai, a member of the administration’s Covid advisory panel, also warned of a possible rebound in cases in June or July, but said the public should not worry as the city had already built strong immunity against the coronavirus.

On Friday, the government announced that groups deemed at high risk of developing severe Covid symptoms would be entitled to a free booster shot this year from April 20, at least six months after their previous dose or infection.

However, other residents would have to pay for their fourth or fifth Covid shot from the private sector from the same date. Health secretary Lo Chung-mau on Saturday said it would be up to private clinics to decide on the charge.

Hung, chief of the University of Hong Kong’s infectious diseases division, told a radio show on Saturday that the government had adopted a “correct and reasonable” approach to focus on care for the high-risk population.