(Bloomberg) -- More Hong Kong residents are getting their first Covid-19 vaccinations, though the majority are receiving a Chinese immunization that studies have shown gives inadequate protection against the recently arrived omicron strain.

The city administered about 18,000 initial injections on Tuesday, the most in four months, as the highly-transmissible variant began spreading in the community and a looming expansion of the vaccine mandate led many people to fear losing access to restaurants and leisure facilities. The jump in first doses outpaced the roughly 16,400 booster shots given. 

The rising demand shows progress is being made against vaccine hesitancy in Hong Kong, a problem particularly among the elderly, where just 22% of the over-80 population has received an initial dose. The recent surge in inoculations came as city leaders announced that people must have at least one vaccine dose to enter restaurants and leisure facilities starting on Feb. 24.

Among the newly vaccinated, 61% opted for a shot from Sinovac Biotech Ltd. that has been shown to be less potent against the omicron strain. The remainder received a shot from BioNTech SE that uses new mRNA technology to target the virus’s genetic makeup. 

Initial studies found that three doses of the BioNTech vaccine are needed for adequate protection against omicron, while even three doses of Sinovac’s shot aren’t enough. Despite this, the Sinovac immunization is often chosen by people trying to avoid the side effects that a potent mRNA shot may carry.

Hong Kong to Widen Vaccine Bubble to Restaurants Next Month

The jump in vaccination comes as evidence emerges that omicron is circulating in the community. The city is working to contain an omicron cluster tied to a packed restaurant at the end of December. Officials also disclosed the first preliminary positive case of Covid-19 from an unknown source in almost three months this week. 

The health department suspects that the patient, an unvaccinated man who works in the densely populated North Point area of the city, carries the omicron variant. Whole genome sequencing still needs to be conducted to confirm if that’s the case, according to a government statement on Tuesday. 

The news raises the possibility that coronavirus may be spreading in the increasingly isolated Asian financial hub via routes of transmission that health officials haven’t been able to trace. 

The government on Tuesday also found a seventh case linked to the restaurant cluster in the 13-year-old daughter of an earlier patient. Another two preliminary cases in people with ties to those with earlier omicron infections were reported early Wednesday. 

The city also recalled a 2,500 passenger cruise ship because nine people onboard are considered close contacts of an infected person in the latest chain of transmission.

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