The Van Trump Report

Why We Still Don’t Have a Vaccine for Avian Influenza

As U.S. poultry losses from highly pathogenic avian influenza HPAI top more than +22 million, the urgent need for a vaccine is once again in focus. The USDA’s chief veterinary officer recently said the agency is looking into possible options. Keep in mind, the last major avian flu outbreak in the U.S. ran from December 2014 to June 2015, when more than +50 million chickens and turkeys either died from highly pathogenic avian influenza (HPAI) or were destroyed to stop its spread. While no one argues that a vaccine would help protect poultry flocks as well as producers, USDA’s Animal and Plant Health Inspection Service (APHIS) warns there are numerous complicating factors to consider, including the potential impact on U.S. poultry exports.

Agricultural Research Service scientists, including those at APHIS, have widely maintained that currently available vaccines are generally not effective. The problem is the same one scientists have with creating a vaccine for human influenza – the virus mutates rapidly. That means a vaccine created for a particular strain today won’t necessarily work with new outbreaks. To work well, vaccines need to match the genetics of the virus. The closer the genetics match to the virus, the more effective the vaccine is.

Poultry stakeholders also worry about the cost of a potential vaccine. Producers would need to vaccinate their entire flocks and could possibly need more than one dose. Depending on a bird’s lifespan, some birds may need a second dose. So the technology needs to be very inexpensive and scalable on a pretty massive level to accommodate the hundreds of millions of poultry birds produced in the U.S. every year.  

Another potential issue is that a vaccine would probably not be able to completely prevent infection, though it would reduce sickness and death. So while a vaccine would reduce the overall viral load, infected birds could still spread the virus. That risk means importers that ban poultry and poultry products from areas experiencing HPAI outbreaks would likely maintain that policy.

Another concern for U.S. exports is that importers might not be able to distinguish between infected birds and vaccinated birds. It could also hinder the ability of flock owners to conduct surveillance testing. According to Chief Veterinary Officer Rosemary Sifford, APHIS is investigating a vaccine that could be distinguished from the live virus that spreads in poultry. USDA is also working with other countries on options for vaccines.

Here in the U.S., Adel Talaat, a professor of pathobiological sciences at the University of Wisconsin School of Veterinary Medicine, is working on a vaccine that would offer domestic birds protection from current and future strains of the virus that emerge over time. The vaccine technology he is implementing, called a nanovaccine, uses tiny particles (smaller than the width of a human hair) to deliver immunity by sending pathogen-like signals to cells.

Another project led by Dr. Yuying Liang, with the UM College of Veterinary Medicine, has developed eight vaccine candidates against H5 and H7 HPAI viruses. The eight vaccine candidates are currently being tested on mice. The next research phase is to evaluate efficacy in a live animal. Supply chain issues caused by the pandemic slowed research progress but UM has patented and licensed Liang’s viral vector. (Sources: USDA, Reuters, Science Daily)

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