H5N1 HPAI Vaccination: The Mexican Experience, 2022–2024
A recent study assessed the efficacy of vaccination against highly pathogenic avian influenza (HPAI) H5N1 in Mexican poultry during emergency campaigns. Vaccines produced through reverse genetics, particularly those derived from H5N8 and H5N1 subtypes, elicited stronger immune responses, reflected by higher seroconversion and seroprotection rates, compared with conventional inactivated H5N2 vaccines.
The results demonstrated that a single dose of reverse-genetics vaccines could induce a favorable immune response, with variability depending on bird type and vaccination period. These vaccines also conferred more sustained long-term immunity with fewer doses, supporting their superior efficacy profile. Commercial layers and parent flocks showed higher seroconversion and seroprotection rates, while turkeys and progenitor flocks mounted weaker responses, indicating species-specific differences in vaccine performance. Although emergency vaccination increased antibody titers, in some cases seroconversion and seroprotection rates remained below 80%, underscoring the need for improved antigenic matching and further optimization of vaccination strategies.
