“Various indicators, including sewage and community monitoring, have shown the local epidemic to be stable and going down,” Chuang said. “Today the cases have fallen below 200, but we can’t rule out there are ups and downs.”

Health officials identified two more infections tied to a cluster at the Lan Kwai Fong Hotel in Sheung Wan, where a couple returning from the United States stayed while infected with the BA.2.12.1 subvariant of the Omicron strain.

The two new patients, a 76-year-old woman and 67-year-old man, were at a McDonald’s branch in Tai Koo Shing at the same time as the couple on May 13. Three other diners at the outlet have also been confirmed as infected.

New cases stoke fears cluster at Lan Kwai Fong quarantine hotel growing

Hong Kong rolled out the fourth round of jabs for residents aged 18 to 59 on Saturday after a joint scientific committee recommended the day before they take another shot if they were at a higher risk of Covid-19 exposure or needed it for travel abroad. A fourth shot should be received at least six months after the third one.

But Lau stressed that the main purpose of vaccination was to reduce severe symptoms and fatalities after infection, and for those aged 18 to 59, three doses provided enough protection.

For this age group, a fourth shot would only function to protect against infection for one to two months, he explained. Receiving the same vaccine over and over would provide less protection after each dose and adverse effects such as myocarditis from the German-made BioNTech vaccine were possible among young people, Lau warned.

“From the perspective of preventing severe conditions or death, people in this age group should absolutely not get a fourth shot,” he told a radio programme.

Experts last month recommended a fourth dose for residents aged 60 years or above, the group hit hardest by fatalities during the recent fifth wave of infections.

Lau said provision of a fourth dose mainly targeted the elderly and those with chronic conditions, such as kidney problems and cancer who needed the booster for protection against severe symptoms and death.

For younger residents, only those who needed to go abroad, medical staff and employees at border quarantine sites might need a fourth jab, he said.

The expert explained the current priority was still to boost the vaccination rate for three doses among the elderly, especially those aged 70 and above, in the next two to three months – the “honeymoon period” that came at the end of the fifth wave before a possible sixth one emerged.

The three-dose inoculation rate stood at 54 per cent as of Monday. But that dropped to 46 per cent among those aged 60 and above, 35 per cent for those 70 and above, and 21 per cent among those aged 80 and above.

Second boosters: what the studies tell us about the fourth Covid-19 jab

Dr Ho Pak-leung, a top microbiologist at the University of Hong Kong, agreed there was no urgency for healthy people to receive a fourth dose.

“For people who are perfectly healthy, from the perspective of preventing serious conditions, there is no pressing need [to take a fourth dose],” Ho told another radio programme.

He said people with chronic illnesses, such as diabetes, kidney failure and obesity, would have a greater need to get their fourth dose.

While new coronavirus variants could leak into the community, Ho added, the focus should be more on whether a rise in serious cases occurred rather than on overall infection figures.

Provided people had completed their vaccination schedule, the arrival of Omicron-related subvariants in the community should be of small concern, he said.

Meanwhile, the health department banned Turkish Airlines from landing in the city from Tuesday to Saturday after one of its flight brought in four passengers who tested positive for Covid-19 upon arrival and two who breached pandemic rules.

The city’s Covid-19 tally stood at 1,210,586, with 9,370 deaths.