Hong Kong residents have swamped clinics to get vaccinated against Covid-19 ahead of the expected reopening of the city's border with mainland China, which some people fear will bring a surge of infections to the financial hub.

City government centres providing shots produced by BioNTech have in recent days been mostly booked solid, some until February, in contrast with a few weeks ago when anyone seeking a vaccine could stroll into a nearly empty facility.

"After the opening of the border, I expect there will be more infected people on the streets, I want to reduce my chance of getting infected,” said a Hong Kong resident surnamed Wan, 33, who got his fourth shot this week.

Hong Kong’s government announced plans to reopen its border and resume restriction-free travel for the first time in more than three years after Beijing abandoned its strict "zero-Covid" policy and announced it was easing its travel restrictions from Jan. 8.

Hong Kong saw a sluggish vaccine uptake when the shots first became available in 2001, particularly among the elderly, but rates picked up over the past year and more than 83% of Hong Kong residents have received three doses of either the BioNTech shot or China's Sinovac vaccine, according to government data.

The number of people getting a fourth shot jumped more than 100 percent this week from a week earlier.

It's not just a fear of new infections after the border reopens but worry that mainland visitors will snap up mRNA vaccines, which can give better protection against Covid but are not available for Chinese residents in the mainland.

Many mainlanders have been asking on social media about how to get an mRNA vaccine in Hong Kong.

Hong Kong's government has said non-residents will have to pay for vaccines at private clinics.

"I'm afraid it might be harder to get vaccinated once mainlanders start coming," said Kevin Lam, 29, queuing up along with dozens of other people for his fourth vaccine at a clinic in the city's Quarry Bay district.

A Hong Kong resident surnamed Tsoi said she was relieved to have made a booking for BioNTech's second-generation booster.

"I'm a bit worried that vaccinations will run out,” the 35-year-old said.

People queue at a community vaccination centre, ahead of an expected border reopening with China, during the coronavirus disease (COVID-19) pandemic in Hong Kong, China, January 4, 2023. (REUTERS/Tyrone Siu)

Hongkongers rush to get vaccinated ahead of mainland border reopening