Hong Kong government vaccine experts have said they do not rule out the possibility of a fourth Covid-19 booster for residents, with the city rolling out third shots under its booster program next week.
The idea, which was raised by David Hui Shu-cheong, a government pandemic adviser, came on the back of official advice issued by the Macau government last week, indicating that the third dose should be given at least 28 days after the second shot, while the fourth should come six months following the third jab.
Authorities of the casino hub also said the extra shots should cover immunocompromised people aged 12 or above.
Hong Kong will start offering booster shots to the elderly and those under high-risk groups from next Thursday. Those who have received the Chinese-produced Sinovac vaccine can also get a third jab even if they are not in the vulnerable category, although such cases will be handled on a discretionary basis by on-site staff.
On Saturday, Hui said the amount of antibodies in a person vaccinated with the Sinovac shot could drop to a low level six to eight months after their second jab. This could be boosted to 97% from about 30% if they opt for the German-made BioNTech jab as their third dose, compared with 58% for another Sinovac shot, according to the expert.
“If the third dose is Sinovac, you may need a fourth shot six or eight months later due to the fall in antibody levels,” Hui told a radio programme. “By contrast, if you opt for BioNTech as your third dose, the antibody levels will shoot up much higher and last longer even as they wane.”
On a separate programme, Wallace Lau Chak-sing, convenor of the advisory panel on Covid-19 vaccines, said although not much data was available to support the necessity of a fourth or fifth dose, it was possible annual vaccinations were needed for residents in the future as antibody levels waned.