As of Thursday, the city’s official case tally stood at 11,836, with 210 related deaths. There were fewer than five preliminary-positive cases pending confirmation.

Professor David Hui Shu-cheong, a Chinese University respiratory medicine expert and government pandemic adviser, warned against reading too much into Thursday’s zero cases, saying one day’s figure did not tell the full story.

“But the overall trend of recent low figures is encouraging,” he allowed.

The apparent success, however, was only likely to increase pressure on the government to further ease social-distancing measures, according to Ramon Yuen Hoi-man, the Democratic Party’s health care policy spokesman. Yuen recommended authorities again raise the limit on public gatherings to 50, as it was around the middle of last year when zero cases were reported.

“Suppression of people’s freedoms is based on the need to control a surging epidemic; that justification is now lost on the back of these numbers today,” he said. “Prolonged restrictions will only increase the burden on mental health.”

The government has linked easing social-distancing rules for many businesses to the vaccination status of workers and customers, prompting complaints about the complexity of the arrangements and strain on their operations.

But, Yuen said: “Without a local epidemic, the government can no longer hold Hongkongers and businesses hostage with vaccination.”

On Thursday, authorities also removed a vaccination centre nurse from the official infection tally after reviewing her test results and contact tracing findings, effectively declaring the case a false positive.

Health officials also formally reclassified 12 cases as being linked to imported ones after concluding that an engineer from Dubai who became the city’s Covid-19 variant infection in the community had indeed caught the virus in a quarantine hotel from a fellow guest on his floor.

Experts, meanwhile, weighed in on the city’s newly proposed “cruises to nowhere” scheme on Thursday, warning there was still an element of risk in spite of the advanced anti-infection protocols.

First announced on Wednesday, the sea voyages will allow residents to travel outside Hong Kong without setting foot in other destinations, and are expected to launch in late July.

Ships are also required to operate at just half capacity, and must immediately return to Hong Kong in the event of any suspected infections on board. If a case is identified, all passengers must undergo testing once back in the city, but whether and how they are quarantined will be based on the public health advice at the time.

However, authorities have not said they will require antibody tests as well – a decision Dr Joseph Tsang Kay-yan, chair of the Medical Association’s communicable diseases committee, said should be reversed.

University of Hong Kong microbiologist Dr Ho Pak-leung told a radio programme on Thursday that foreign crew members arriving in the city should undergo three weeks of quarantine and be tested twice for Covid-19 antibodies to ensure they were no longer in the infectious period.

Cruise operators should also avoid swapping crew members in and out between voyages, as testing alone was not stringent enough to prevent outbreaks. Ho also said no one on board should be exempted from vaccination when the cruises launched, and that operators should take things slow at first so staff could get used to the arrangements.

Phoebe Yip Ching-man, vice-president of Dream Cruises’ marketing department, said passengers would be given a tracking device that would alert them if they were standing less than 1.5 metres away from another passenger. She said the devices had already been used on the company’s cruises in Singapore, so staff had experience ensuring passengers carried them and complied with other measures.

The company’s ship will also provide PCR testing on board, as well as more than 50 negative pressure quarantine rooms to be used if any passengers test positive for the coronavirus.

“Those of us within the industry have joked that cruises are suddenly the safest places in Hong Kong, because all the crew members and passengers are vaccinated,” Yip said. 

But for some Hongkongers, the idea of a cruise held little appeal. Dentist Alan Lam Kwing-tong and his wife were among the thousands of passengers trapped for days on board the coronavirus-stricken Diamond Princess cruise ship last year.

“Generally speaking, I support the cruise to nowhere offer and the requirement to have passengers vaccinated,” he said. “But my wife and I are still suffering from cruise phobia. We don’t think we will consider a cruise for the coming five years.”

Another cruise fan, who gave her name as Yeung, said she would refrain from travelling for the rest of this year because of the unstable coronavirus situation in Hong Kong and elsewhere.

“Even in Hong Kong, I will avoid crowds, not to mention thousands of people on a cruise ship,” she said. “Another issue I am concerned about is the side effects of vaccines, and I will wait some time before getting vaccinated. So I won’t be qualified to join the voyages.”

Additional reporting by Denise Tsang and Kathleen Magramo