The Consequences of Egg Adaptation in the H3N2 Component to the Immunogenicity of Live Attenuated Influenza Vaccine

Adaptation in egg-passaged vaccine strains may cause reduced vaccine effectiveness due to altered antigenicity of the influenza haemagglutinin. Here, we tested whether egg adaptation led to an altered antibody response to the H3N2 component of the Live Attenuated Influenza Vaccine. We showed that twice as many vaccinated children seroconverted to an egg-adapted H3N2 strain than the equivalent wildtype strain. However, there was a slightly stronger mucosal IgA response to wildtype antigen driven by responses in pre-vaccination seropositive children. Sequencing of virus from nasal swabs showed there was low sequence diversity in the nose and no reversion of egg-adaptive mutations.