Hong Kong has rolled out a fourth round of jabs against Covid-19 for residents aged between 18 and 59, with some health experts suggesting the dose should not be made compulsory given the limited data available about its efficacy. The launch of the expanded scheme came as authorities vowed on Saturday to keep a “close eye” on a co-educational secondary school in Southern district after the emergence of a small cluster of infections involving three students from the same class. The city logged 228 new Covid-19 cases on the same day, including 16 imported ones, taking the overall tally to 1,210,159. With no new deaths reported, the number of fatalities related to the virus remained at 9,370. The government announced the launch of the fourth round of vaccinations a day after recommendations were presented by a joint scientific committee under the Centre for Health Protection. “Experts considered that a [fourth vaccine dose] in younger populations may provide transient additional protection against infection and symptomatic diseases,” a government spokesman said. “Some people may want to receive a fourth dose due to personal needs, such as studying abroad or to fulfil a requirement for overseas travel.” Healthcare workers or those in care homes, as well as personnel involved in anti-pandemic work, might also be considered to be at higher risk of exposure, the spokesman added. Walk-in vaccinations for the fourth jab opened on Saturday for individuals deeming themselves at higher risk of exposure to the coronavirus and who have received their third dose at least six months prior. Authorities also revealed that adults aged between 18 and 59 who had previously contracted Covid-19 could take their third jab six months after they received their second shot or had recovered from the virus, depending on whichever event was the most recent. Both the China-produced Sinovac shot and the German-made BioNTech jab are available. Walk-ins will continue until an online booking system is in place on May 26. At a vaccination centre offering Sinovac jabs in North Point, the Post observed dozens of residents receiving their third dose, with many not yet qualified to get a fourth. A woman, who only gave her surname as Ng, said she arrived at the centre to get her fourth shot at around noon but was told she needed to wait another week to complete the six-month interval between receiving her third and fourth jabs. “The epidemic hasn’t ended yet. I want to protect myself and my family,” Ng said, adding that her job involved frequent contact with the public, leading her to worry about the risk of infection. But a 45-year-old man, who gave his surname as Chong, said he would only get a fourth jab if it was made mandatory by authorities. “With three jabs, I can dine in restaurants [under the upcoming vaccine pass requirement], so I don’t need an extra one,” he said. More transmissive Omicron strain detected in Hong Kong but expert unfazed But government pandemic adviser Professor David Hui Shu-cheong said the new round of jabs could benefit people in high-risk jobs, such as restaurant employees, during a possible sixth wave of infections. Hui said the fourth jab would also provide additional protection to residents travelling overseas, noting that other countries might not require certain health measures such as wearing masks. “There is no need [to make a fourth jab mandatory for the wider public] because they are not aged above 60 or immunocompromised, they don’t have such a need comparatively,” he said. “We have limited information on the effects of a fourth dose for residents aged under 60. It can only raise your antibody level for two to three months.” Second boosters: what the studies tell us about the fourth Covid-19 jab The government adviser added that receiving three doses of either Sinovac or BioNTech would be sufficient to prevent severe illness or death as a result of Covid-19. Infectious disease expert Dr Leung Chi-chiu also said there was currently limited information on the side effects of receiving a fourth jab, such as data on the potential risk of developing myocarditis among recipients below the age of 30. Leung questioned whether administering a new dose would protect residents until winter, with the measure potentially creating the need for a future fifth jab. Instead, he suggested the general public wait for the launch of a new vaccine. Since early April, the fourth vaccine dose has been available for residents aged 60 or above. As of Saturday, more than 96,300 had received such jabs. Comparatively, more than 91.8 per cent of the population aged three or above have received their first dose while 86.4 per cent have got a second dose. But only 53 per cent of residents aged 12 or above have had a third shot. Addressing the emergence of the new cluster, Dr Albert Au Ka-wing, principal medical and health officer at the Centre for Health Protection, said two Secondary One students from the same class at a school in the Southern district were reported to be infected with Covid-19 on Friday after undergoing rapid testing. Four days before their reported infections, Au said another classmate also tested positive. He noted that all three male students had each received one vaccine dose. Au declined to disclose the school’s name, but Hong Kong University Graduate Association College issued a statement on Saturday night confirming the infections. The campus had gone through thorough sanitisation and would continue with face-to-face teaching on Monday, the statement said. “The other 30 students in the same class all tested negative over the past week,” Au said. “So far there have not been any new cases. We’ve asked the school to disinfect the campus and will keep a close eye on the situation there.” Coronavirus infection can lead to severe bone loss, Hong Kong researchers warn Au said authorities had not ruled out the possibility that the three students were infected at the same time while at school, adding that the rest of their classmates would need to undergo rapid testing over the weekend. “We’ll examine their test results tomorrow. If there are more cases we’ll consider temporarily closing the school or requiring the students to conduct a nucleic acid test,” he said, adding that the infection rate among Hong Kong schools was only 0.013 per cent, with 785,000 students undergoing tests over the past week. Authorities also said the vaccine pass would apply to 13 types of public healthcare premises providing non-emergency medical services from June 13. The categories include specialist outpatient clinics, student health service facilities and women’s health centres. Patients who cannot comply with the arrangement will instead need to provide a negative polymerase chain reaction test result completed 48 hours before their visit. Any accompanying family members will still be required to adhere to the scheme. Hong Kong to push on with third stage of vaccine pass scheme, 328 cases logged But the government stressed such measures would not apply to public emergency healthcare premises, including accident and emergency departments, general outpatient clinics, elderly health centres or maternal and child health facilities. Professor Philip Li Kam-tao, president of the Hong Kong College of Physicians, told reporters after a Saturday radio programme that the current vaccination rate of more than 50 per cent for the third dose was not ideal. Li said he was not in a position to comment on whether a further grace period should be given for residents to get inoculated, but he stressed the importance of the booster shot. Earlier on the programme, Li said Hongkongers were experiencing pandemic fatigue, so there was a need to ease social-distancing curbs, but a vaccine pass would prevent a rebound in cases, as the 200 to 300 infections reported each day indicated there were still transmission chains in the community. He also proposed scrapping the city’s flight suspension mechanism to allow “Hong Kong to reconnect with the rest of the world”, saying the seven-day quarantine for inbound travellers would be enough to weed out imported cases. Additional reporting by Nadia Lam