Influenza vaccination, hospitalizations, and costs among members of a medicare managed care plan

OBJECTIVE. To evaluate the effectiveness and possible cost savings of influ enza vaccination. SUBJECTS. Members age 65 and older in a Medicare managed care plan during t he 1994-1995, 1995-1996, and 1996-1997 influenza seasons. RESEARCH DESIGN. The study examined administrative data on influenza vaccin ation and subsequent hospitalizations. Outcomes included hospitalization wi th pneumonia or influenza, with any respiratory condition, and with congest ive heart failure (CHF). RESULTS. Vaccinated subjects experienced fewer hospitalizations with respir atory conditions or CHF than had unvaccinated subjects (OR = 0.8 (95% CI, 0 .7, 0.9) in analyses adjusted for age, sex, pneumococcal vaccination, healt h utilization, and morbidity). Analyses adjusted in addition for ethnicity obtained similar results among the subgroup of members whose ethnicity was known. Subjects without major disease in the previous 12 months had lower o dds ratios for vaccination than subjects with major disease (OR values of 0 .5 [95% CI, 0.4, 0.7] and 0.9 [95% Cl, 0.8, 1.1], respectively). Subjects a ges 65 to 79 had lower odds ratios for vaccination than subjects ages 80 an d older (OR values of 0.7 [95% Cl, 0.6, 0.9] and 0.9 [95% Cl, 0.8, 1.1], re spectively). Estimated cost savings averaged about $80 per vaccinated subje ct. CONCLUSIONS. Subjects ages 65 to 79 who had received influenza vaccination experienced fewer hospitalizations and had lower costs than had unvaccinate d subjects. Associations were weaker for subjects age 80 and older. The res ults, consistent with recommendations for the use of influenza vaccine, sug gest that people ages 65 to 79 should be heavily targeted for vaccination.