Government medical advisers have recommended that Hongkongers aged 60 and above get a fourth shot of Covid-19 vaccine, given that most of the coronavirus-related deaths recorded in the city’s fifth wave of infections involved the elderly.

The joint scientific committee of the Department of Health published its recommendations on Thursday, saying the fourth dose should be given at least three months after the third shot for better protection.

It also made clear residents in other age groups need not receive a second booster as prevailing medical evidence showed one was enough to prevent severe illnesses.

“Three doses of the vaccination in other age groups are very effective in preventing hospitalisation and death,” said Dr Albert Au Ka-wing, of the Centre for Health Protection, adding that authorities would continue to monitor the scientific developments on whether additional doses were needed for other age groups.

The committee also said it had “no objection” to authorities’ proposal to allow recipients of other vaccines – such as ones for seasonal flu – to be administered Covid-19 jabs on the same visit, as long as they gave informed consent, paving the way for boosting uptake especially in residential care homes.

The experts had previously recommended that Covid-19 vaccines should be administered at least 14 days before or after any others.

Health authorities confirmed 2,644 Covid-19 infections on Thursday, the second day the number of fresh cases dipped below 3,000, while 97 deaths were reported.

The city’s overall tally now stands at 1,183,235 cases, with 8,557 fatalities.

Au said the death toll had fallen slower than the daily caseload. “There could be one or two weeks between infection and death,” he explained.

Among the deaths reported on Thursday, the Hospital Authority’s Dr Lau Ka-hin said a 27-year-old man, who had chronic asthma and had previously required intensive care for his condition, died suddenly at home on Wednesday after being discharged from hospital with a low viral load reading on March 18.

The man, who was not vaccinated, was given antibiotics and some medicine upon discharge, Lau said, adding that he was unable to answer whether the man had contracted the virus during his hospital stay.

Officials at the public mortuary would decide whether an autopsy was needed to determine the man’s cause of death, Lau said.

An expert panel found that while three doses were effective at preventing severe illness, seniors should receive a fourth for better protection.

With a three-day, mass self-screening exercise using rapid antigen tests set to begin on Friday, the government also reminded residents in a press release to upload their positive test results within 24 hours and attach a photo of the result to the health department’s self-declaration website.

Residents are also urged to refrain from going out.

“We are seeing 2,000 to 3,000 cases in the community every day, meaning that there are still transmission chains,” Au said, as he called on residents to take part in the voluntary programme. “We hope to find out all the cases in a short space of time [via the self-screening].”

The joint committee said its recommendation of a fourth dose was based on the fact that the vast majority of recent Covid-19 deaths occurred among the elderly.

Over 95 per cent of the more than 8,300 Covid-related deaths recorded in the fifth wave involved people aged at least 60.

Some countries, such as Israel, Britain and France, have already started giving out fourth doses to their elderly citizens.

In Hong Kong, immunocompromised people, such as those undergoing cancer treatment and recipients of organ transplants, are currently allowed to get a fourth dose three months after their third.

The experts also noted in their latest recommendations that people who were not sure whether they had been infected with Covid-19 previously could still receive the vaccine.

“Covid-19 vaccine is safe in people with evidence of previous Sars-CoV-2 infection,” they said. “Prior Covid-19 screening before administration of Covid-19 vaccine is not required.”

Separately, the committee said that residents who were partially inoculated outside Hong Kong with locally unavailable Covid-19 jabs could complete their course with a suitable locally available alternative at least four weeks after their last dose, provided their first shots were approved for emergency use by the World Health Organization.

For those who had fully or partially inoculated with shots not on the WHO’s list, the experts recommended they start a fresh course using the vaccines available in Hong Kong.