Avian influenza vaccines and vaccination in birds.

Although the use of vaccines against avian influenza viruses in birds has been discouraged over the years, the unprecedented occurrence of outbreaks caused by avian influenza (AI) viruses in recent times has required review of this policy. A variety of products are now available on the market, ranging from inactivated conventional to live recombinant products. The general consensus on the use of vaccination is that if complying to GMP standards and properly administered, birds will be more resistant to field challenge and will exhibit reduced shedding levels in case of infection. However, viral circulation may still occur in a clinically healthy vaccinated population. This may result in an endemic situation and in the emergence of antigenic variants. In order to limit these risks, monitoring programmes enabling the detection of field exposure in vaccinated populations are recommended by international organisations and are essential to allow the continuation of international trade. Adequate management of a vaccination campaign, including monitoring, improved biosecurity and restriction is essential for the success of any control program for AI.