Immunogenicity and efficacy of commercial poultry avian influenza vaccines against HPAI A(H5N1) clade 2.3.4.4b viruses in Mexico

Abstract

The high-pathogenicity avian influenza A (H5N1) viruses of clade 2.3.4.4 b have been detected in domestic poultry and wild birds in Mexico. Vaccination with H5 vaccines has been implemented as a complementary influenza control strategy in poultry in many countries, including Mexico. Continuous reevaluation of the efficacy of licensed vaccines against emerging viruses is required to ensure adequate control of virus transmission and infection. Some commercial poultry H5 vaccines used in Mexico are produced from vaccine seed viruses that are genetically distinct from clade 2.3.4.4 b viruses. Here, we studied the efficacy of four commercial H5 poultry vaccines widely used in the Mexican market and an experimental inactivated, adjuvanted vaccine against a recent North American high-pathogenicity avian influenza A (H5N1) 2.3.4.4 b virus. Chickens in all vaccinated groups developed antibodies to the viral nucleoprotein as detected by enzyme-linked immunosorbent assay. Although some of the commercial vaccines did not elicit detectable hemagglutination inhibition or microneutralization titers, all vaccines provided 80 %–100 % protection from mortality. Immunophenotyping of the peripheral blood mononuclear cells of vaccinated chickens showed that these vaccines did not elicit peripheral T-cell or other non-B cell responses that could explain the observed protection. Accordingly, we recommend continued evaluation of vaccine efficacy against evolving viruses and further efforts to identify non-neutralizing antibody correlates of protection.