Immunity to influenza in older adults with chronic obstructive pulmonary disease

Background. Chronically ill older adults constitute a population vulnerable for complications associated with influenza. Study of their immunity to influenza virus may help design better strategies to stimulate protective immune responses. Methods. Immunogenicity of influenza vaccines and immune protection from natural influenza were assessed in older adults with chronic obstructive pulmonary disease as part of a vaccine efficacy trial. Subjects received either trivalent inactivated influenza virus vaccine (TVV) intramuscularly and trivalent live cold-adapted influenza virus vaccine (CAIV-T; n = 1107) intranasally (inl) or TVV and placebo inl (P; n = 1108). Results. In the subsets of study subjects assessed, serum hemagglutination inhibition ( HAI) and nasal- wash antihemagglutinin ( HA) immunoglobulin (Ig) A and IgG antibody levels and anti-influenza virus CD8(+) cytotoxic T lymphocyte activity increased after immunization. Mean postimmunization nasal-wash IgA antibody levels to influenza A H3/HA and B HA were statistically higher in the TVV+CAIV-T group (n = 957) than in the TVV+ P group (n = 951). Postimmunization serum HAI and nasal-wash IgA antibodies to influenza A/H3N2 and B viruses were associated with a reduced relative risk for natural influenza infection. Conclusions. TVV+ CAIV-T appeared more immunogenic than TVV+P, but the observed difference may be clinically unimportant. Anti-influenza serum and nasal-wash antibodies were associated with immune protection.