Vaccination of gallinaceous poultry for H5N1 highly pathogenic avian influenza: Current questions and new technology

•Use of vaccine for AIV in poultry, remains controversial due to numerous technical, regulatory and political concerns.•H5N1 high pathogenicity AIV represents one of the largest scale uses of vaccine for AIV in gallinaceous poultry.•There are numerous characteristics of avian influenza virus vaccines which are critical to their efficacy and potency.•Inactivated whole virus vaccines are the most common platform for AIV in poultry and represent the highest use by dose.

Vaccination of poultry for avian influenza virus (AIV) is a complex topic as there are numerous technical, logistic and regulatory aspects which must be considered. Historically, control of high pathogenicity (HP) AIV infection in poultry has been accomplished by eradication and stamping out when outbreaks occur locally. Since the H5N1 HPAIV from Asia has spread and become enzootic, vaccination has been used on a long-term basis by some countries to control the virus, other countries have used it temporarily to aid eradication efforts, while others have not used it at all. Currently, H5N1 HPAIV is considered enzootic in China, Egypt, Viet Nam, India, Bangladesh and Indonesia. All but Bangladesh and India have instituted vaccination programs for poultry. Importantly, the specifics of these programs differ to accommodate different situations, resources, and industry structure in each country. The current vaccines most commonly used are inactivated whole virus vaccines, but vectored vaccine use is increasing. Numerous technical improvements to these platforms and novel vaccine platforms for H5N1 vaccines have been reported, but most are not ready to be implemented in the field.