The third and final stage of the vaccine pass, which will require people to be triple-jabbed to enter restaurants and regulated premises such as bars, gyms and cinemas, takes effect on May 31.

Nip's comments came after two University of Hong Kong scholars wrote on Ming Pao yesterday asking authorities to ditch the "no jab, no entry" requirement for adults under 60 as they are very unlikely to develop serious illnesses and death upon contracting Covid, adding it is "meaningless" to pursue a higher jab coverage among the age group.

Epidemiologist Benjamen Cowling and pharmacist Chan Tak-kwong said the health system will not collapse even if young people are not fully vaccinated or refuse to be vaccinated.

Around 6.67 million or 91.6 percent of people aged above three have had at least one jab and some 6.25 million, or 86.5 percent, have had two.

However, Nip argued only 68 percent of people between 20 and 60 have received the third jab and that the current protection is still insufficient.

He called on the public to receive their booster shots as soon as possible to develop a stronger immune barrier so social distancing measures can be relaxed and the public can carry on with their normal lives.

Nip added that authorities implemented the three-jab requirement for employees and visitors at government buildings yesterday.

Meanwhile, a study by HKU and the Chinese University of Hong Kong said double-vaccinated people can generate up to six times more antibodies after contracting the Omicron variant compared to those with no jabs.