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

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.

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.

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.

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.