The Omicron was officially designated a “variant of concern” by the World Health Organization on Friday.

Jin said that Omicron has a higher number of mutations, and there was evidence showing that people who have recovered from Covid-19 can still be infected by the variant.

"Considering that there is a small outbreak in South Africa, it is presumed that the variant is better equipped to evade immune responses, including vaccine-induced immunity than other variants," he said.

He reminded that people with immune deficiencies need to pay more attention to this variant, but it's too early to say whether it will trigger a bigger outbreak.

"Not only AIDS patients, but also other people with immune deficiencies such as people taking anti-rejection drugs for organ transplants or immunosuppressive drugs against tumors... they need to be aware of Omicron," Jin said.

Jin added that the next step is to conduct genetic sequencing of the virus in different countries to find out the extent of Omicron transmission in each country.

He pointed out that all the countries need to take more active measures to protect those with compromised immune responses, including giving them priority to booster jabs and testing their antibodies.

Separately, Ivan Hung Fan-ngai, a co-convenor of a government panel on vaccine reactions, said that the local vaccination rate needed to be increased to 99 percent before people can skip quarantine while crossing the border with the mainland or go overseas.

In a TV program on Sunday, Hung said that the government should expand the vaccine bubble by requiring the public to receive two Covid-19 jabs before entering all the restaurants, cinemas and public places.

Even when people are exempted from quarantine while crossing the border, they should still be tracked and required to undergo tests, he said.

He added that the number of Covid-19 cases may increase when border controls are lifted, so it is necessary to maintain the existing rigorous case tracking routine.