HONG KONG - Hong Kong's top officials said on Monday that the city's vaccine programme would be expanded to include more priority groups including teachers and delivery workers, as fears grow over a series of adverse reactions following the vaccine rollout.

At least two people have died and several fallen seriously ill after receiving a vaccination by China's Sinovac. The government has said it is still assessing the causality between the incidents and the vaccine and would report findings as soon as possible.

Around 93,000 people have been vaccinated since the public rollout started on Feb 26.

"These serious adverse events are of much concern to us," Sophia Chan, the city's health secretary, told a news briefing on Monday. "We are still uncertain whether it was related to the vaccine. Once we have any information or conclusions, we would report the details to the public."

Bookings for vaccinations have dropped in recent days according to government figures that show around 4,900 people booked their Sinovac vaccine on March 5, compared with 12,300 people on March 3.

Chan said people who were unsure about their own medical situation should consult a doctor before booking the vaccine.

Hong Kong is due to start administering the Pfizer/BioNTech vaccine this week. Until now Sinovac has been the only option available.

Patrick Nip, the city's secretary for the civil service, who was speaking at the same news conference, said seven additional preferential groups would be allowed to apply for vaccines including, those working in catering, in supermarkets and convenient stores and public transport workers such as bus drivers.

To try to assuage fears, Matthew Cheung, the city's secretary for administration, wrote on his blog on Sunday that the government would do a "good job of vaccination monitoring and respond to social concerns to protect public health and give citizens peace of mind".

(Reporting by Farah Master; Editing by Alex Richardson) ((farah.master@thomsonreuters.com; +852 3462 7709;))