Despite global health officials saying the risk of transmission of a new strain of avian flu from birds to humans is low, leading vaccine manufacturers say they could make hundreds of millions of jabs for humans within months if the virus were to leapfrog the species divide.
One current outbreak – H5N1 clade 2.3.4.4b – has killed record numbers of birds and infected mammals so far, but human cases, however, remain very rare, reports Reuters.
GSK, Moderna and CSL Seqirus, owned by CSL Ltd, are already developing or about to test sample human vaccines that better match the circulating subtype, as a precautionary measure against a future pandemic.
Others, like Sanofi “stand ready” to begin production if needed, with existing H5N1 vaccine strains in stock.
Unsurprisingly, most of the potential human doses are earmarked for wealthy countries in long-standing preparedness contracts, said global health experts and the pharma companies.
“We could potentially have a much worse problem with vaccine hoarding and vaccine nationalism in a flu outbreak than we saw with Covid,” said Dr Richard Hatchett, chief executive of the Coalition for Epidemic Preparedness Innovations (CEPI), which helps fund vaccine research.
An international framework for pandemic flu allocates 10% of global supply for the World Health Organisation to share with low- and middle-income countries. By contrast, the WHO is seeking guarantees of 20% global supply for other types of pandemic in the wake of Covid.
The agency said it has signed legally binding agreements with 14 manufacturers for 10% of their pandemic flu vaccine “as it comes off the production line", in a mix of donated doses and doses to be bought by the agency at an affordable price.
WHO did not comment on the potential for vaccine hoarding in a flu pandemic but said mechanisms were being developed “so that countries can work together – not in competition with each other” to respond to such a crisis.
There are close to 20 licensed vaccines against the broader H5 strain of flu. Existing antiviral treatments for people already infected will also help mitigate the impact.
However, moving to large-scale production of a more targeted shot could take months, the manufacturers said.
“Creating the first dose is the easiest,” said Raja Rajaram, head of global medical strategy at CSL Seqirus. “The hardest is manufacturing in large quantities.”
Moderna’s mRNA vaccine research actually began with pandemic flu, and was modified for Covid, said Raffael Nachbagauer, executive director of infectious diseases at Moderna.
The company plans to launch a small human trial of an mRNA pandemic flu vaccine tailored to the new avian influenza subtype in the first half of 2023, he said, adding Moderna could respond “very quickly” in an outbreak scenario.
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