Alice strain live attenuated influenza (H3N2) vaccin in an elderly population

The clinical and antibody responses to Alice strain (AS) live attenuated influenza A (H3N2) vaccine and killed parenteral (KP) bivalent influenza vaccine were compared in a randomly allocated group of 150 elderly volunteers. AS recipients experienced more symptoms but these were mild and short in duration. Rhinitis occurred in 45% and pain at injection site in 25% of the AS and KP groups, respectively. Influenza A (H3N2) serum hemmaglutination inhibition titer responses were significantly higher in KP vaccinees; 95% of KP AND 60% OF AS recipients with initial titers smaller than or equal to 1:16 had fourfold or greater titer rises. KP induced significantly higher nasal neutralization titers but the proportion with fourfold or greater responses was not significantly different. Previous studies have shown poor correlations between antibody levels induced by live influenza vaccines and protection. Natural and/or challenge studies are needed before efficacy of influenza vaccines can be established.