Are we prepared for it if bird flu starts spreading between humans?

Australia is well placed to quickly create a vaccine should a strain of bird flu infect the human population, according to experts.

Although cases of bird flu infecting humans are rare, and only limited, non-sustained, human-to-human transmission is thought to have occurred, it is a risk which is being widely discussed.

Raina MacIntyre, head of the Biosecurity Program at the Kirby Institute at the University of New South Wales and an expert in influenza and emerging infectious diseases, says that we are well prepared for human vaccines in such a case.

“If a pandemic arises, once the genome sequence is known, and exact matched vaccine can be made in 6 weeks with mRNA technology and 4 months using the old egg-based methods.

“Australia is fortunate to have influenza vaccine and mRNA manufacturing capacity onshore, which many countries do not have. The regulatory process may take longer, but we can expect to have vaccines sooner than we did for COVID-19.”

MacIntyre ‘s remarks are supported this week by a review study in the peer-reviewed journal Human Vaccines & Immunotherapeutics, which assessed avian influenza pandemic preparedness.

The review looked at current human vaccine capability for H5N1, H7N9, and H9N2 subtypes in particular.

“The H5N1, H7N9, and H9N2 subtypes of avian influenza virus pose a dual threat, not only causing significant economic losses to the global poultry industry but also presenting a pressing public health concern due to documented spillover events and human cases,” says lead author Flavio Cargnin Faccin of the University of Georgia in the US.

“This deep delve into the landscape of avian influenza vaccines for humans shows vaccination remains the primary defence against the spread of these viruses.”

The review found that inactivated vaccines are a safe and affordable option that primarily activate humoral immunity – the part of our immune system that produces antibodies.

“Live attenuated influenza vaccines, on the other hand, induce a broader immune response, encompassing humoral, mucosal, and cell-mediated immunity,” the authors write.

“This makes them potentially more protective, despite concerns about their safety.”

The review also examined alternative vaccine platforms, such as virus-like particle (VLP) vaccines and messenger RNA (mRNA) vaccines, that have emerged more recently.

They conclude: “exploring and employing a diverse range of vaccine platforms is crucial for enhancing pandemic preparedness and mitigating the threat of avian influenza viruses.”

Last week Agriculture Victoria confirmed 2 strains of high pathogenicity avian influenza (HPAI) had been detected at separate poultry farms in Meredith and Terang, 110 km away. The strains detected are HPAI A H7N3 and H7N9, respectively.

The properties are directly linked through joint management, staff and machinery. However, testing at CSIRO’s Australian Centre for Disease Preparedness laboratory confirmed that these strains are genetically related to low pathogenicity avian influenza (LPAI) strains detected in Australian wild birds.

The outbreaks were caused by separate spillover events of LPAI from the wild bird population into domestic poultry, where they mutated into HPAI viruses. To date, there have been no reported human cases linked to the outbreaks.

In the US, amidst an ongoing multistate outbreak of the HPAI A H5N1 virus clade in dairy cows, a second human case has been identified in Michigan.

Similar to the first case in Texas, the patient reported symptoms consistent with an eye infection, not a respiratory infection.

Vinod Balasubramaniam, a virologist at the Jeffrey Cheah School of Medicine & Health Sciences at Monash University in Malaysia, says: “human infections are rare and typically result from close contact with infected birds or contaminated environments.”

But he says the virus’s ability to undergo genetic reassortment or mutation heightens concerns as “mutations enabling efficient human-to-human transmission could trigger a pandemic.”

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