Immunogenicity and safety of a novel liposomal influenza subunit vaccine (INFLUSOME‐VAC) in young adults

Influenza and its complications account for substantial morbidity and mortality among young adults and especially among the elderly. In young adults, immunization provides 70–90% protection, while among the elderly the vaccine may be only 30–40% effective; hence the need for new, more immunogenic vaccines. We compared the safety and immunogenicity of a novel IL‐2‐supplemented liposomal influenza vaccine (designated INFLUSOME‐VAC) with that of a commercial subunit vaccine and a commercial split virion vaccine in young adults (mean age 28 years) in the winter of 1999–2000. Seventy‐three healthy young adults were randomly assigned to be vaccinated intramuscularly with the following: a commercial subunit vaccine (n = 17, group A), INFLUSOME‐VAC (n = 36, group B), and a commercial split virion vaccine (n = 20, group C). The three vaccines contained equal amounts of hemagglutinin (∼15 μg each) from the strains A/Sydney (H3N2), A/Beijing (H1N1), and B/Yamanashi. INFLUSOME‐VAC induced higher geometric mean HI titers and higher‐fold increases in HI titers against all three strains, compared with the two commercial vaccines. In addition, seroconversion rates for the A/Sydney and B/Yamanashi strains were significantly higher ( P  < 0.05) compared with the split virion vaccine, and significantly higher for the three strains compared with the subunit vaccine (69–97% vs 35–65%, P  ≤ 0.02). Moreover, the anti‐neuraminidase response was significantly greater ( P  = 0.05) in group B vs group A. INFLUSOME‐VAC caused mild local pain at the injection site in a significantly higher proportion of the vaccinees (83%). Thus, INFLUSOME‐VAC is an immunogenic and safe vaccine in young adults. J. Med. Virol. 69:560–567, 2003. © 2003 Wiley‐Liss, Inc.