Epidemiologist, Benjamin Cowling warned that otherwise the SAR risks being left behind as other centers achieve herd immunity and return to normal.

Cowling, from the University of Hong Kong, said the government should consider reducing quarantine requirements for children of fully-vaccinated people, to boost the inoculation rate.

Cowling said the SAR had the capacity to vaccinate up to 50,000 people a day, but only around 30,000 people were getting a jab.

"Now that every adult's got the opportunity to be vaccinated, then I think it's really maybe justifiable now to think about vaccine passports to incentivise vaccine uptake. That strategy worked very well in Israel," Cowling told RTHK.

One possibility was policies for children, he said.

"So, for example, the close contact quarantine or on arrival quarantine into Hong Kong," Cowling said.

"If it was relaxed for vaccinated people, there would still be an issue with their children. If they came with children the children have to go into quarantine and then the parents have to go anyway so maybe think about relaxing that as well."

Separately, the restaurant sector saw a pickup in business on Mother's Day, with a turnover of about HK$350 million.

Simon Wong, the chairman of the Hong Kong Federation of Restaurants & Related Trades, told RTHK that turnover was still down 15 percent from last year.

He said this was mainly because most eateries could seat only four people per table and had to close at 10-pm, due to pandemic restrictions.

Under the government's “vaccine bubble” scheme, restaurants can set up specific areas to seat more customers per table, and Wong said those restaurants that had vaccinated staff and could seat up to six people per table and stay open until midnight saw business jump 10 to 15 percent compared to the same period last year.

He said the jump would encourage more staff to get vaccinated.

"For the past week we have already seen a lot of staff taking the vaccine," he said, adding that they were getting the jab so they could go back to work.

"I would estimate that there are already about 60 percent of catering industry staff who have taken the vaccine," Wong said.

The head of the Medical Association, Choi Kin, said on Sunday that distrust of the authorities was holding back Hong Kong's efforts to persuade its citizens to accept Covid-19 vaccinations, but stressed that inoculation was the only hope in the fight against the virus.

Separately, a recent survey of unvaccinated adults found that an overwhelming majority of respondents were not motivated to undergo inoculation against coronavirus, despite the government’s “vaccine bubble” initiatives that offer relaxed social distancing rules for those who’ve received the jabs.