Serological Monitoring of an H5 Inactivated Vaccine in Layer Farms, Iran, 2018

Background and Aims: Avian influenza (AI) is an acute infectious disease of poultry, waterfowl, wild birds, and animals, zoonotically transmitted to humans. Some incidents of HPAI are reported in Iran: H5N1 and H5N8. Iranian Veterinary Organization decides on vaccination (H5) of layer and breeder flocks in high-risk provinces following the outbreak in Iran. This study aimed to evaluate the serum response of the vaccine in the layer flocks of high-risk provinces. Materials and Methods: Ten laying farms (Size: 30000-50000) were selected from Qazvin (no: 2) and Isfahan (no: 8) provinces that received the H5 vaccine (Four farms: 1 time; 6 farms: 2 times of vaccine shots). Twenty-five blood samples were taken from each flock. The HI test was carried out in a U-bottomed microtiter plate and 4 HA units of homologous antigen. Results: The mean titers of antibodies in the poultry farms that received the vaccine once were 1.87, while those that received the immunization twice were 4.90 (significant difference; p<0.05). Also, if we consider protection baseline 4, 4 out of 6 flocks (~67%) could make it above it. Injection of the vaccine twice also improved CV. Conclusion: In combination with other control measures such as good biosecurity and monitoring programs, vaccination is considered a suitable and powerful tool to support AI eradication or control programs in endemically infected countries if the Iranian Veterinary Organization (IVO) did regular post-vaccination surveillance and evaluated the flocks for silent infections.