Among the new cases reported on Thursday, 48 were imported and 116 locally transmitted. The number of untraceable cases also continued to grow, with authorities unable to find the sources of a dozen community infections recorded across various neighbourhoods, including Ho Man Tin, Ma On Shan and Tin Shui Wai. About 100 people tested preliminary-positive.

The city’s total number of confirmed cases to date stands at 13,790, with 213 related deaths, while 662 Covid-19 patients are being treated in public health care facilities, all of them in a stable condition.

Centre for Health Protection controller Dr Edwin Tsui Lok-kin warned that the risks of more outbreaks in the community remained very high.

“Currently there are more than 30 cases without traceable source of infection, suggesting that there are at least dozens of hidden transmission chains in the community,” Tsui said.

“It is purely based on science,” Lam said, adding that the quarantine period had already been shortened for close contacts of confirmed Covid-19 cases. “There is no logic, no consistency if we still impose the 21 days on arrivals as they are not even close contacts.”

The government will also scrap the highest-risk category of nations and places deemed to pose an Omicron threat, which required returning residents to quarantine at Penny’s Bay for four days before moving to a designated hotel for another 17 days of observation. Instead, travellers from those countries will be treated the same as ones from high-risk countries.

Flights from eight countries, including Australia, India, Britain and the United States, remain banned until February 18.

Lam conceded that reducing the quarantine period by seven days would not be enough to satisfy the business community but further reduction would be “a very dangerous move” for Hong Kong.

“We do not possess the prerequisites for living with the virus because the vaccination rate is not good, especially among the elderly,” she said. “I could not stand seeing a lot of old people dying in my hospitals.”

In a bid to boost the inoculation rate, the government will expand the vaccine bubble to cover more premises and rename the effort “vaccine pass”. Under the programme, all patrons and workers at venues and areas covered by the bubble must show proof of having received at least one shot. The requirement would eventually be stepped up to three shots, Lam said, but the public would have plenty of time to prepare.

Nearly 79 per cent of the eligible population has received at least one dose and Lam said that once the rate reached 90 per cent, the government would re-evaluate the overall situation.

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Authorities will also take a more aggressive approach in encouraging residents at homes for the elderly or people with disabilities to take the jabs. Inoculations would be administered once a resident is deemed suitable by a doctor and has given consent. In order to be admitted to the facilities, new residents will have to show proof of having received at least one dose.

While quarantine requirements for arrivals will be relaxed, the government is extending social-distancing rules for residents for at least another two weeks. Bars, gyms, cinemas and a dozen other types of businesses will remain shut until February 17, while students would continue to learn from home until February 21, Lam revealed.

“As the epidemic has got more serious and there could be large-scale outbreaks at any time, therefore the government can neither relax nor fine-tune any social-distancing measures currently in place,” she said.

People who are medically proven unfit for Covid-19 vaccination will be issued with an exemption certificate, which can be displayed with the “Leave Home Safe” app.

Given the surge in patient numbers, the Hospital Authority is preparing to take over two more halls at AsiaWorld-Expo to provide an additional 500 beds to treat patients with mild symptoms and it plans to hire more retired or part-time nurses for the necessary shifts.

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Officials are also setting up a second contact-tracing office and increasing the number of staff assigned to the task to 500, up from 350.

Lam said she had already asked Guangdong authorities to help Hong Kong ramp up laboratory testing capacity, but noted it would be “far more difficult” for mainland China to send medical staff to hard-hit housing blocks to carry out testing or provide counselling to residents due to the language barrier and its different approach to fighting Covid-19.

The outbreak at Kwai Chung Estate continued to grow, with more cases uncovered at six blocks, taking the total number of infections at the housing complex to 372. Some residents from Nga Kwai House were evacuated due to possible vertical transmission, while three of the 16 towers remain under lockdown.

Lam said that lockdowns at Yat Kwai, Ying Kwai and Ha Kwai Houses could end on Friday and Saturday as scheduled.

Authorities also sent some residents from the nearby On Kwai House at Kwai Fuk Court into quarantine after vertical transmission was suspected to have taken place.

Vertical and horizontal transmission was also believed to have occurred at Cheung Bor House at Choi Wan Estate in Ngau Chi Wan, after 23 cases were reported across 16 flats. Experts believe a security guard working at the tower, who is the mother of a hamster owner earlier confirmed to have Covid-19, is the index case at Cheung Bor House. Fears of animal-to-human transmission linked to hamsters prompted a massive government cull of the small rodents on January 18.

As a precaution, all residents from units 7 and 11 on all floors, as well as those from units 2 to 7 on the 16th floor, will be sent to a quarantine centre. Other residents in the building must isolate at home for a certain period of time, which will be decided later, according to authorities.

Additional reporting by Nadia Lam and Gary Cheung