Evaluation of a recombinant hemagglutinin expressed in insect cells as an influenza vaccine in young and elderly adults.

Healthy subjects <45 years old (young adults) or >65 (elderly adults) were randomized in double-blind fashion to receive intramuscularly subvirion trivalent influenza vaccine, placebo, or 15, 45, or 135 microgram of the hemagglutinin (HA) of the influenza A/Beijing/32/92 (H3N2) virus expressed in insect cells by a recombinant baculovirus (rHA0). All vaccines were well tolerated. Both young and elderly adults manifested serum hemagglutination-inhibition, virus neutralizing, and HA-specific IgG ELISA antibody responses to rHA0 vaccine. In young adults given 135 microgram of rHA0, the vaccine was significantly more immunogenic than subvirion influenza vaccine. Elderly adults also had increased antibody responses to 135 microgram of rHA0 compared with subvirion vaccine, but the difference was not statistically significant. These results demonstrate that high-dose rHA0 vaccines are well tolerated and effectively induce both functional and binding serum HA-specific antibody in young and elderly adults.