A comparative immunogenicity-reactogenicity dose-response study of influenza vaccine

This study examined the immunogenic and reactogenic responses of influenza vaccine in 29 healthy nonallergic adults at three vaccine dosages: 0.5 mL, 0.1 mL, and 0.05 mL. After immunization a 7-day assessment of adverse reactions was made and serial serum hemagglutination-inhibition (HAI) antibody responses were measured during a 28-day period. The incidence of adverse reactions was significantly decreased in the group receiving 0.1 mL and 0.05 mL compared with the group receiving 0.5 mL of vaccine. After immunization with 0.1 mL or 0.05 mL vaccine increases in serum HAI antibody to A/Leningrad, A/Taiwan, and B/Ann Arbor influenza antigens were seen comparable to those observed after 0.5 mL. However the magnitude of these rises were lower and were directly correlated with the dose of vaccine. Since immunization of egg-sensitive allergic patients with influenza vaccine poses a risk of localized and systemic reactions, a common clinical practice is to prevent such reactions by vaccine dilution. Although the results of the present study suggest that vaccine dilution results in a decrease in adverse reactions, there is also the risk of decrease protective immunity with this procedure and therefore the practice should not be condoned.