Sixteen others who were also arrested at the same time have been quarantined, while 15 police officers involved in the operation at the Sam Ka Tsuen Recreation Ground, in Yau Tong, on Friday tested negative for the coronavirus, but five officers considered to be close contacts had been quarantined.

Dr Chuang Shuk-kwan, head of the Centre for Health Protection’s communicable disease branch said while the Ursus Fitness cluster, which had grown to 142 cases on Sunday, had mostly been brought under control, the city was still seeing infections with unknown sources and should remain vigilant.

“We have still recorded some unknown cases here and there, so I think there is still some silent transmission in the community,” she said.

Meanwhile, Professor Ivan Hung Fan-ngai, co-convenor of an official panel on vaccine reactions said people should take a half-day or one day off for rest after taking the second shot.

The first batch of Sinovac recipients, including Chief Executive Carrie Lam Cheng Yuet-ngor and other officials, were expected to get their final jabs from Monday.

“Foreign data suggested that the side effects brought by the booster are stronger than the first dose. Recipients may witness more severe swelling, fever or fatigue,” Hung said on a television programme on Sunday.

Hong Kong hotel owners pin hopes on vaccines, travel pass to revive sector

Hung said those who experienced mild side effects – such as palpitation and dizziness – after getting their first jab of either the Sinovac or BioNTech vaccine, should seek medical advice before receiving the second dose.

But he warned that recipients who were hit by more serious symptoms, such as facial paralysis, were advised not to take the booster at the moment.

Hung said that, in the interest of better protection, they would generally not advise people to casually switch their choice of shot between doses.

However, the expert committee would look into setting up a mechanism that would allow those who underwent severe side effects after the first dose to take a different type of booster several months later following a clinical assessment, he added.

Under the current rules, recipients of Covid-19 jabs can postpone their booster shots for no more than four weeks.

Hung said the antibodies brought on by the first dose would only last for around six months, and would gradually decrease from that point onwards.

Hung, a clinical professor of medicine at the University of Hong Kong, also revealed that the school would soon embark on a study looking into the outcome of taking a combination of vaccines, as they believed there might be a chance it would yield better results.

HKU will recruit at least 50 people to join the study, which would involve them receiving an injection of the Pfizer-BioNTech vaccine first, and one of Sinovac 28 days later.

So far eight people – most of them chronically ill – have died in the days after receiving a jab. No link between the deaths and the vaccine has been established.

Hong Kong doctors, patients groups push for better guidance on vaccine side effects

Two people also suffered from Bell’s palsy – a temporary paralysis of the face – after receiving the Sinovac shot, but experts monitoring the Covid-19 inoculation scheme could not establish any connection between the two.

According to the latest official figures, so far some 354,400 residents – or about 4.7 per cent of the city’s population – had received their first dose of vaccine. About 233 700 received Sinovac, while around 120,700 got the BioNTech jab.

The chairman of the government’s expert advisory panel on vaccines, Professor Wallace Lau Chak-sing, told another news programme there had not been any statistical data showing an increase in stroke or coronary heart disease rates following the roll-out of the jabs.

Lau said that according to Hospital Authority data, between 40 and 50 people were diagnosed with strokes, and 20 to 30 with coronary heart disease, every day, while out of those eight and 10 died of the respective illnesses. Those numbers had not changed since the vaccine roll-out, he said.

03:55

Inside Hong Kong's mandatory coronavirus quarantine camp at Penny's Bay

Inside Hong Kong's mandatory coronavirus quarantine camp at Penny's Bay

Separately, the Licensed Bar and Club Association of Hong Kong called for the city’s establishments to be allowed to reopen before Easter, saying the subsidy of HK$50,000 was barely enough for businesses to survive after being ordered to close for more than three months.

Bars, karaoke lounges, nightclubs and party rooms have been closed since November 26, when Hong Kong faced its fourth wave of coronavirus infections.

Association president Ben Leung Lap-yan also said while licensed bar operators could face jail time for violating the closure notice, illegal bars had sprung up to serve the city’s residents but only faced fines when they were caught.

Also among Sunday’s new cases was a 28-year-old woman from the Philippines, who arrived last Thursday. She had stayed at the Ramada Hong Kong Grand Hotel, and had been sent to quarantine.

A 71-year-old substitute taxi driver tested preliminary-positive, and his customers should have received a notification from the Leave Home Safe app, officials said.

Meanwhile, HSBC said its headquarters in Central would reopen on Monday. It was closed for deep cleaning and disinfection last week, after three people working in the offices tested positive for the virus.