Comparison of the safety, tolerability, and immunogenicity of a MF59-adjuvanted influenza vaccine and a non-adjuvanted influenza vaccine in non-elderly adults

The adjuvanted influenza vaccine FLUAD™ is composed of subunit influenza antigens combined with the MF59-adjuvant emulsion. The vaccine was developed primarily for use in elderly populations, but non-elderly individuals might also benefit. To evaluate this hypothesis, 301 healthy adults were assigned randomly to receive two intramuscular injections of either FLUAD™ (150 subjects) or a non-adjuvanted vaccine, Fluzone™ (151 subjects), in two trials conducted at a 1-year interval. Injections consisted of 15μg per 0.5ml dose. Vaccine composition was A/Texas/36/91 (H1N1), A/Johannesburg/33/94 (H3N2), and B/Harbin/7/94 for the first injection and A/Texas/36/91 (H1N1), A/Nanchang/933/95 (H3N2), and B/Harbin/7/94 for the second injection. Immunogenicity was evaluated at 28 and 180 days post-immunization. FLUAD™ was generally well tolerated in healthy adults when compared with Fluzone™. FLUAD™ was associated with increased pain at the injection site after immunization. A statistically significant increase in the incidence of injection-site warmth, chills, myalgia, and analgesic/antipyretic use occurred in the FLUAD™ group after the first injection but not after the second injection. In both groups, most of these local and systemic reactions were classified as mild. FLUAD™ was more immunogenic than Fluzone™ following both injections. After the first injection, statistically significant differences were found in the percentage of subjects with four-fold rises in hemagglutinin inhibition (HI) titers at 28 days post-immunization for the B antigen. After the second injection, the FLUAD™ group had significantly higher HI titers, a significantly higher percentage with a four-fold increase in titer, and a significantly greater percentage of subjects with titers ≥160 for the H3N2 antigen at 28 days. Only minor immunogenicity differences between the two groups were seen at 180 days. Compared with Fluzone™, FLUAD™ was associated with increased immunogenicity and mild post-immunization reactions in healthy adults. The magnitude of increased immunogenicity in healthy adults was less than that seen in elderly populations.