Ho said published third-phase data on Sinovac clinical trials involving the chronically ill and those aged 60 and above remained insufficient, noting that mainland authorities had recommended residents in those two groups not receive the shot yet.

Asked on a radio show whether elderly people and such patients should pick BioNTech, he said: “If you strictly follow the data available and the drug label, that would be ideal.”

He said more than 10 million people had already taken the BioNTech jab in the United States, Britain and Israel, making a mass amount of data available for the vaccine, which was jointly developed by German and US firms.

“Overall, it’s very safe,” he said. “So if we work in accordance with the data available, then give clear advice about the two vaccines should be diverted [among various groups] there will not be information confusion,” he said.

But Professor David Hui Shu-cheong, a respiratory medicine expert at Chinese University and government pandemic adviser, noted the clinical study of Sinovac – which analysed more than 400 people aged above 60 years old – had determined its efficacy rate could still hit 51.1 per cent for the age group if the second shot was injected within 14 days.

“Although the number of participants is small, there are signals that its efficacy rate is 51.1 per cent. So it’s hard to restrict them based on their ages,” said Hui, who is also a member of the expert advisory group on vaccines.

“If there had been a need to direct residents to take specific shots, the advisory group would have suggested it.”

He added that a phase-two clinical study of 350 people aged above 60 indicated that antibodies were developed at a reasonable level after two doses, too.

Hong Kong’s vaccination scheme, under way since last Friday, currently provides only Sinovac shots, with the BioNTech version becoming available from next week.

On Tuesday night, health authorities revealed the death of the 63-year-old, who had suffered shortness of breath two days after being vaccinated in late February, sparking concerns over the safety of the drugs.

Vaccination centres deem dozens unfit for Sinovac jab; city records nine new cases

An expert committee monitoring the side effects of vaccines made a preliminary conclusion his fatality was not related to the Chinese-produced jab.

In February, Director of Health Dr Constance Chan Hon-yee said two scientific committees under her department had reviewed trial data and decided those aged above 85 years, those who are bedridden or otherwise physically frail, and those with a fever would be advised not to get a BioNTech jab.

A fact sheet on Sinovac from Hong Kong’s health department states that only 5.1 per cent of participants in the phase-three clinical trial conducted outside China were 60 years old or above, so the efficacy data for this group was insufficient. For this age category, health status and exposure risks should be considered before taking the jab, it said.

But Ho said different doctors could have varying views as to the suitability of those aged 85 and above for vaccination, as the government’s explanation was not clear enough.

He said a small number of people would need to seek advice from their doctors before inoculation, and suggested the government arrange consultations for them.

“Most of the elderly and those living on a low income cannot afford [the fees for consultation]. So if the government doesn’t follow the Sinovac drug label for elderly people and chronically ill patients, it should arrange for some clinics to provide free consultation for these residents,” he said.