IN PREVIOUSLY IMMUNIZED ELDERLY ADULTS INACTIVATED INFLUENZA-A (H1N1)VIRUS-VACCINES INDUCE POOR ANTIBODY-RESPONSES THAT ARE NOT ENHANCED BY LIPOSOME ADJUVANT

In a randomized double-blinded study, 77 healthy elderly seropositive volunteers (95% of whom had received influenza vaccine within the prio r 5 years) were immunized with either monovalent liposome-adjuvanted o r control Subvirion vaccine containing inactivated influenza A/Taiwan/ 1/86 (HIN1) virus. The experimental vaccine was well-tolerated but eli cited serologic responses that were no different in frequency or magni tude from those induced by the control vaccine. Less than 20% of subje cts in either group mounted a fourfold or greater rise in antibody tit er. Sixty-three elderly subjects who had participated in the liposome vaccine trial were reimmunized 18 weeks later with licensed trivalent subvirion vaccine and their serologic responses were compared with tho se of 26 young adults, Significant rises in hemagglutination inhibitio n (HAI) antibody titers to the A/Texas/36/91 (HIN1), A/Beijing/32/92 ( H3N2) and B/Panama/45/90 components occurred in 10%, 76% and 56% of el derly vaccinees, respectively, compared to 92% (p < 0.0001), 100% (p < 0.005) and 88% (p < 0.005) of young vaccinees, respectively. Age diff erences in seroresponse rates to the HIN1 subtype antigen were signifi cant even when comparing young and old adults with identical prevaccin ation HAI antibody titers. These data confirm prior observations sugge sting that previously immunized elderly persons have impaired serologi c responses to influenza vaccines, particularly against recently circu lating HIN1 subtype antigens. It remains un clear whether liposome-adj uvanated formulating would have an advantage over conventional influen za vaccines for routine annual reimmunization of targeted populations.