Comparative Assessment of Seroconversion in Poultry Vaccinated with Two Avian Influenza Vaccines

Abstract

From August to December 2020, a new outbreak of H5 avian influenza caused another serious animal health emergency in Kazakhstan, leading to the deaths or culling of more than 500 000 chickens. This outbreak renewed interest in developing prevention strategies for this re-emerging infection. In this study, we evaluated poultry seroconversion levels after two H5 vaccines. Regardless of age, productivity, and scheme of vaccination Super Nick layers (a total of 368 heads) received a single dose of an inactivated whole H5 vaccine or a baculovirus-derived H5 vaccine, respectively. We assessed the seroconversion by Hemagglutination Inhibition (HI) and Enzyme-Linked Immunosorbent (ELISA) assays. Cloacal and tracheal swabs were tested for Influenza A Virus (AIV) by real-time PCR to monitor the field AIV circulation. The analysis of 368 serum samples showed that the inactivated vaccine provided a significantly higher humoral immune response when compared to the baculovirus-derived vaccine as evaluated by both ELISA and HI in 30, 60, and 120 Days Post-Vaccination (DPV). Thus, our study demonstrates that under farm conditions classical Inactivated Avian Influenza (AIV) vaccine induces a higher seroconversion level against the H5N1 virus predicting better protection against field infection, than a baculovirus-derived H5 vaccine.