About 6,000 people were vaccinated on the first day of the roll-out, and with slots for the next two weeks already booked, officials announced that 200,000 more places would be made available from next Monday until March 26. Three more vaccination centres would also provide China’s Sinovac vaccine, they said.

Also on Friday, the Legislative Council’s Finance Committee approved a HK$1 billion Covid-19 vaccine indemnity fund to provide financial support to people who might develop serious side effects after getting their shots.

“We are seeing slightly more cases … [including] unlinked cases. Many of them reported that they had quite some gatherings over the Chinese New Year, after [the holiday], and also more activities than before. Maybe we are seeing the effect of those gatherings,” said Dr Chuang Shuk-kwan, head of the Centre for Health Protection’s communicable disease branch.

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Officials were particularly concerned about the Tsim Sha Tsui restaurant hit by at least 30 confirmed and suspected infections, ordering all diners who had visited the premises last Friday to undergo quarantine.

“Tables on the ground floor of the restaurant are placed closely together … a super-spreading event might have taken place,” Chuang said.

The source of the outbreak was likely to have been a restaurant cleaner who also helped clear tables, officials said. The cleaner started coughing on February 18 and went to work until 4pm on February 19.

“Even though [the cleaner] was wearing a mask, it does not completely prevent the spread of the virus. At that time, [the person] was coughing so there could be some droplets remaining in the air for some time, so the customers could have been infected this way, ” Chuang said.

Eighteen of Friday’s newly confirmed cases were locally transmitted, including 12 linked to the restaurant, she said.

So far, 11 patrons, including 10 who visited the restaurant for lunch last Friday, as well as five employees and three close contacts of those infected, were confirmed with the virus.

Eleven people, including seven customers, linked to the outlet tested preliminary-positive.

“There were 76 people who had lunch on February 19 in that restaurant, according to records of bills,” Chuang said. “We believe it was rather high-risk [to get the virus] during the lunch hours on February 19.”

She said nine people who were there had called the health authorities, and eight others were identified through the handwritten contact information required for customers at restaurants. All of them had been sent to quarantine.

At least seven of the more than 20 preliminary-positive cases did not have a clear source of infection, a proportion Chuang described as “quite a lot”.

Six of the latest confirmed cases were imported, including two with mutated virus strains – a passenger from Pakistan and another from Ukraine.

The city has recorded 43 infections with mutated strains so far, including 27 with the variant identified in Britain. Four were related to the South African strain, three similar to Brazil’s and nine others had not yet been determined.

The total tally of confirmed cases rose to 10,950, with 198 related deaths.

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Meanwhile, health authorities are looking to enhance their virus tracing measures by widening the criteria for quarantining patients’ close contacts.

Chuang noted the “significant proportion” of unlinked cases in recent weeks, which prompted officials to study the feasibility of implementing stricter measures.

Close contacts who interacted with an unlinked case up to a week before the patient’s onset of symptoms could be sent to quarantine centres, an increase from two days currently.

Chuang said authorities did not routinely quarantine close contacts of patients during the incubation period, usually advising them to get tested.

Under the proposed measures, household members of close contacts who develop symptoms will need to quarantine for three days and test negative before they are released. But if the close contact tests positive, the isolation period for family members will be extended.

Officials are also considering issuing compulsory testing orders for workplaces with a single infection, down from the current threshold of two cases.

In another development, the Hospital Authority revealed that one of two lab contractors processing specimens for Covid-19 tests failed to provide results within 48 hours as stipulated in the contract, resulting in some people waiting more than a week.

The authority declined to name the lab involved at a regular Covid-19 briefing on Friday, but a source said the company was Prenetics.

Authorities also revealed that 14 of the patients linked to the Tsim Sha Tsui restaurant had used the government’s “Leave Home Safe” risk-exposure app. Chuang said at least one patient in the cluster was identified after receiving an alert from the app and going for a test.

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App downloads have exceeded 2.96 million since it was released in mid-November.

But respiratory medicine specialist Dr Leung Chi-chiu said the app only notified users who had one minute of overlap with infected people at a venue.

“Aerosol droplets can remain in the air for hours, so the alert will not be very useful,” he said. “Even if users do not receive a notification from the app, it doesn’t mean they’re not at risk. The public should check if they visited a place with infections around the same time to see if they should get tested.”

Separately, three community vaccination centres at Tseung Kwan O, Kwai Tsing and Tuen Mun, originally slated to provide BioNTech shots, will offer Sinovac jabs from March 6 after the online booking system reopens.

“We saw there was an overwhelming response and that many people would like to get vaccinated early. We responded to this demand and made arrangements as best we could,” Secretary for the Civil Service Patrick Nip Tak-kuen said.

The mainland vaccine would be offered in the three centres for 56 days, but Nip did not say whether they would also provide BioNTech jabs, which were expected to arrive in the city on Saturday morning, after that period.

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The next phase of registration at the other five centres and 18 general outpatient clinics will cover March 12 to March 26, and private doctors will begin receiving shipments of the vaccine on Monday.

Quality Healthcare, which operates one of the three centres involved, said the latest plan had “no material impact” on its preparations.

Health minister Sophia Chan Siu-chee said authorities had not received any unusual reports from the more than 500 people who had received the Sinovac vaccine earlier in the week.

Five patients were sent to the newly opened North Lantau Hospital Infection Control Centre, a temporary facility targeting those with mild to moderate symptoms.

Dr Michael Wong Lap-gate, the hospital’s deputy chief executive, said they expected to take several dozen patients from the community facility in the neighbouring AsiaWorld-Expo in coming days.

Additional reporting by Cannix Yau