Development and evaluation of an inactivated oil emulsion monovalent H5N8 Avian Influenza Vaccine for poultry

Avian influenza (AI) is a highly contagious viral disease affecting poultry worldwide. It significantly impacts the poultry industry, causing economic losses. Developing effective vaccines is crucial to enhance immune response and control infections. The H5N8 is a subtype of highly pathogenic avian influenza virus (HPAIV), causing severe outbreaks in 2016–2017 across Egypt, Korea, Europe, and other regions. Mallards experienced high mortality at medium and high viral doses, while chickens required higher doses for fatal outcomes. Vaccination is the most effective strategy to control the spread of HPAI H5N8, helping to reduce infection rates and prevent outbreaks. This study focused on developing a monovalent inactivated oil-emulsion H5N8 vaccine using the Egyptian HPAI H5N8 strain (A/Chicken/Egypt/F71-586C/2022). Montanide ISA-71 VG served as the oil adjuvant. The final vaccine underwent sterility, safety, and potency testing. The potency of the prepared vaccine was evaluated by measuring the antibodies response of vaccinated chickens using HI test in addition resistance to challenge virus. It proved to be safe, sterile, and effective, with antibodies detected from the first week post-vaccination. Levels peaked at week three, reaching 10 log₂, before declining to 8 log₂ by the experiment's end. Vaccinated birds exhibited 90% protection against H5N8, showing mild clinical signs but no mortalities.