Health experts in Hong Kong have recommended that children aged three years and above be able to receive the Sinovac Covid-19 vaccine, in a move that will push the city closer to the goal of mass immunity.

The major development on Monday came as health officials made further progress in an investigation into a “Delta Plus” Covid-19 cluster involving three Cathay Pacific pilots, announcing that a German hotel, the Hyatt Regency Mainz near the city of Frankfurt, was suspected to be the source of the coronavirus scare.

Mainland Chinese drug maker Sinovac last month applied to city authorities to lower the minimum vaccination age for its coronavirus shot from 18 to three. Neither of the two drugs currently approved for use locally are available to children under the age of 12.

A late-night government statement said the advisory panel on Covid-19 vaccines recommended after a meeting on Monday that three- to 17-year-olds now could receive the Sinovac shot.

Officials will decide later who gets priority within that age group.

Hong Kong is within touching distance of achieving mass immunity, having inoculated more than 4.67 million people, or 69.5 per cent of its eligible population, with one dose of a vaccine.

Some scientists say herd immunity can be attained if 70 per cent of the population is vaccinated, sufficiently cutting down transmission and offering enough protection in the community.

But local officials and experts have often stressed the need for near-universal coverage to build up not just a protective barrier in the city, but also to gain Beijing’s approval to restart quarantine-free travel with the mainland.

Respiratory medicine specialist Dr Leung Chi-chiu said he believed Monday’s decision would put the city on a path to achieving sufficient immunity as unvaccinated children and adolescents around the world had become one of the biggest groups transmitting the virus.

“We have seen this in school outbreaks on the mainland and across the world,” Leung said. “Lowering the age threshold for Sinovac’s vaccine is also the safe and responsible thing to do.”

He said further lowering the age limit for the BioNTech vaccine was “not worth the benefit” because of a risk of heart inflammation and other side effects in children.

Earlier in the day, William Chui Chun-ming, president of the Society of Hospital Pharmacists of Hong Kong, said more than 100 million children between the ages of three and 17 had been vaccinated on the mainland.

But the available data on Sinovac trials for children remained limited, especially for those aged under five, he told a local radio programme, adding the advisory panel should look at more evidence before following the mainland’s lead. That argument, however, was based less on Sinovac’s safety – there have been few reports of adverse effects – than concerns over its effectiveness.

“Sinovac’s efficacy rate among adults is only about 50 per cent. So will children also need a third shot?” Chui asked, referencing a recent government recommendation that residents inoculated with the vaccine get a booster shot.

No children under the age of 12 are currently allowed to be vaccinated in Hong Kong.

The advice last month from the joint scientific committee under the Centre for Health Protection (CHP) specified that taking the BioNTech jab as a booster was preferable.

Given the higher efficacy rate of the German-made vaccine, at more than 90 per cent, Chui suggested experts discuss whether it could also become an option for children aged five to 11.

Health authorities lowered the age limit for the BioNTech vaccine to 12 in June, but the company has not submitted applications seeking to further reduce it.

Chui also noted that the mainland was so far the only place in the world where children as young as three had been approved to receive the Sinovac vaccine.

Chile had lowered the age limit for the vaccine to six, while Brazil would decide later this month whether to allow children aged three to 11 to receive it, he said.

In an exclusive interview with the Post earlier this month, senior Sinovac executives said the latest data showed their vaccine was safe for babies as young as six months old.

On the Delta Plus-cluster front, the CHP also said that anyone in Hong Kong who had stayed at the Hyatt Regency Mainz this month would have to undergo quarantine in a government isolation facility for 21 days.

Children walk past the Choi Hung Road Badminton Centre, a distribution point for the BioNTech vaccine.

The hotel came into officials’ focus after three Cathay Pacific cargo pilots who had stayed there at the start of the month later tested positive for the sub-lineage of the Delta variant.

Two of the pilots checked in on November 1, while the third one arrived on November 3, with all three saying they had not left their rooms during their stay.

The centre said in a statement: “Epidemiological investigations showed that the three people could have been infected during their hotel stay, and an outbreak in the hotel could not be ruled out.”

It added that it had notified the German authorities so they could follow up on the situation.

Separately, the centre confirmed six imported infections on Monday, involving arrivals from South Africa, Germany, the Netherlands, the Philippines and Pakistan. The local tally now stands at 12,387 infections, with 213 related deaths.

Monday also saw the new policy of separating mainland and overseas arrivals at Hong Kong airport take effect, a key measure touted to increase Beijing’s confidence in fully reopening the border.

Most travellers the Post spoke to said they did not experience much inconvenience.

Kimi, 30, a frequent business traveller between the city and Shanghai before the pandemic, said that beside a new testing centre, the rest of the process remained much the same as in June.