High-risk groups include residents aged 50 or above, people aged 18 to 49 who have chronic illnesses, the immunocompromised, pregnant women and healthcare workers. Others will have to pay for their fourth or fifth dose at private clinics.

Residents who are not part of the high-risk groups can still receive the first three jabs for free if they have never been infected before. If they wish to receive additional boosters they need to pay for them at private clinics.

Those who made bookings before April 20 will not be affected by the changes.

2. Why did health authorities make the changes?

The changes follow the government’s joint scientific committee’s recommendations on Wednesday advising high-risk groups to get an additional booster at least six months after their previous jab or Covid infection.

“Antibodies drop six months [after vaccination or infection],” said Professor David Hui Shu-cheong, who chairs the scientific committee on emerging and zoonotic diseases.

Hong Kong pandemic adviser defends Covid vaccine plan to charge for boosters

“High-risk groups are at risk of fatal and severe diseases … if there is a new variant a few months later and their antibodies have dropped, they will not be protected.”

The experts added the additional shot could be Sinovac or BioNTech’s bivalent or ancestral strain vaccines.

Healthy adults aged 18 to 49, and children aged six months to 17 years with underlying comorbidities could choose to take the extra shot based on personal preference, they added.

According to health authorities, three doses offered enough protection to those who did not belong to any priority groups.

3. How did the city respond to the changes?

Ivan Hung Fan-ngai, a government adviser at the University of Hong Kong, welcomed the changes, saying public resources should be prioritised for vulnerable groups.

“I believe that residents who need to travel, and are cautious of their higher infection risks, will be willing to pay for the booster out of their own pockets,” he said.

City resident Frances Ho, 29, who is triple-vaccinated, said she had no plans to take the fourth dose.

“I don’t want to suffer from side effects again because I got a fever last time,” said Ho, who works in the media industry. “I also managed to stay Covid-free when my whole family was infected during the peak of the pandemic, so I believe three doses are all I need.”

Ruby Chung, 32, a public relations specialist who is also triple-vaccinated and remains uninfected, said he did not plan on taking an extra dose.

“If the government starts to charge people for vaccines, it means the pandemic has stabilised and the virus is no longer that fatal,” she said.

High-risk group should still get additional Covid jabs, Hong Kong experts say

4. Will authorities suggest a flat rate for the booster?

No. Health minister Lo Chung-mau made it clear on Sunday that it was up to the private market to determine the price, adding the practice would be in line with flu jabs.

Dr Samuel Kwok Po-yin, president of the Association of Private Medical Specialists of Hong Kong, whose clinics offer both free and paid vaccine services, said it was reasonable for the private market to decide the prices as the booster programme was not sponsored by the government.

Kwok said he expected the booster price to be more than HK$1,000 (US$875. “Different organisations might adjust the price level according to demand,” he said. “But I don’t think the charge will be unreasonable due to keen competition.”

5. Is there demand for boosters in Hong Kong?

Daily vaccination figures have been declining after Lunar New Year holiday in late January, with the weekly average dropping below the 2,000 mark since March.

As of Friday, close to 84 per cent of residents have received three doses, but only 32 per cent of children aged from three to 11 have been triple-vaccinated.

About 1.1 million residents have had the fourth dose, and more than 73,000 have taken the fifth one.

Kwok said he believed not many people would rush to make appointments before April 20 for the free shots.

“Hongkongers generally are not very motivated to get inoculated now,” he said. “A lot of residents have also tested positive previously and might not meet the criteria to receive the booster [at least six months] after the previous jab or infection.”

According to the programme’s booking website, government clinics offering vaccine services are almost fully-booked until May. Demand for Sinovac shots is high at private clinics, while demand for BioNTech is lukewarm.

Community vaccination centres have plenty of spots open, except for a few designated for children.

No rush for Covid vaccine booster shots among mainland Chinese visitors in Hong Kong

6. What are the World Health Organization’s recommendations?

The WHO on Tuesday revised its vaccine recommendations, with high-risk groups advised to receive an additional booster after either six or 12 months after the last dose. The timeframe depends on factors such as age and immunocompromising conditions.

For medium-risk adults, a fourth or fifth booster is no longer recommended.

The WHO’s experts stressed that the advice was for the current epidemiological scenario only.

Additional reporting by Jeffie Lam