Experts split over second-generation vaccine purchase
BioNTech’s Omicron-targeted booster has backers and detractors on government’s advisory panel
Government health advisers were yesterday divided over whether Hong Kong should buy BioNTech’s Omicron-targeted coronavirus booster shot, with some saying it was more effective than the first-generation jabs, while another claimed the purchase would be a waste of resources.
Their comments came as Hong Kong recorded its first Omicron XBB.1 subvariant from an imported case, but health experts warned against undue alarm over the more transmissible strain and said no policy change was needed.
The government on Sunday said it was examining an application from Germany’s BioNTech to make the booster shot available. The request would then be handed over to the 11-member advisory panel on Covid-19 vaccines, chaired by government adviser Professor Wallace Lau Chak-sing, for review.
Professor Ivan Hung Fan-ngai, a top infectious disease expert and a member of the advisory panel, said authorities should introduce the new booster shot against the dominant BA.4 and BA.5 Omicron strains.
“Same as with influenza, even though the variant used to develop the vaccine may not be entirely the same as the prevalent strain, the jab can still boost immunity,” he told a radio programme.
The second-generation BioNTech booster contains a bivalent formulation, meaning it is based on two virus strains – the original Covid-19 type, as well as the BA.4 and BA.5 lines, while a monovalent vaccine is only based on one strain.
Citing preliminary data from the United States, Hung said that even if the vaccine, whether monovalent or bivalent, was developed using the BA.1 Omicron strain, it would still be more effective against subvariants such as BA. 2, BA.4 and BA.5 than the first-generation drug, which was based on the original Covid-19 strain.
Omicron subvariants BA.4 and BA.5 are at present the dominant strains in Hong Kong, accounting for 93.9 per cent of samples tested by health authorities.
Professor David Hui Shucheong, also a member of Wallace Lau’s vaccine advisory panel, agreed with the call to acquire the new booster jab. He cited the World Health Organization, which had recommended that governments purchase “a broad range” of vaccines that target different variants to give themselves “a plurality of options” when formulating inoculation policies.
The comments were contrary to fellow member Professor Lau Yu-lung, who on Sunday said such a move would be a waste of resources and untimely, as data proved that vaccines currently available could prevent serious symptoms and death.
Lau added the new booster might become outdated as a few imported cases involving another new variant, BA. 2.75, had been recorded in Hong Kong.
The Centre for Health Protection yesterday reported the first imported XBB.1 strain from a 50-year-old woman who arrived on September 25 from the US. The strain was also previously reported in Singapore and India.
But Hui said the latest strain was “just another Omicron variant but with high transmission potential”, while there was currently not much clinical data on it. “Variants emerge all the time. No need to worry if vaccination rates [are] high,” he said.
Respiratory medicine specialist Dr Leung Chi-chiu also said there was no cause to panic, as there was no evidence of a community spread yet. “When travel resumes after we drop quarantine, import of emerging variants is what we should expect. No need to change [policy] until there is an actual danger signal in the real world,” he said.
Hong Kong yesterday logged 4,874 Covid-19 infections, 396 of which were imported. There were 10 more virus-linked deaths reported. The city’s Covid-19 tally stands at 1,806,688 infections and 10,228 fatalities.
Meanwhile, Hung said that while the Omicron subvariant BA. 2.75 might replace BA.4 and BA.5 and become the prevalent strain, most infections were mild or asymptomatic.
“[BA. 2.75] may be more transmissive than BA.5 and have a much stronger immune escape ability,” he said. “But the public need not be too worried. Evidence show BA. 2.75 and BA.5 have similar severity, causing mostly mild or asymptomatic cases.”
He added that with wide vaccination coverage and most of the population having been infected, the city had a high hybrid immunity against the subvariant.
Hung said studies showed that BA. 2.75 was resistant to Evusheld, an antibody injection drug available in the city’s hospitals, which lowered its efficacy, while antiviral drugs remained effective against the subvariant.