title: Influence of high-risk medical conditions on the effectiveness of influenza vaccination among elderly members of 3 large managed-care organizations.
abstract: This serial cohort study assessed the risk of hospitalization or death associated with influenza and the effectiveness of influenza vaccination among subgroups of elderly members of 3 managed-care organizations in the United States. Data on baseline characteristics and outcomes were obtained from computerized databases. A total of 122,974 (1996-1997 season) and 158,454 (1997-1998 season) persons were included in the cohorts. Among unvaccinated persons, hospitalizations for pneumonia/influenza or death occurred in 8.2 of 1000 healthy and 38.4 of 1000 high-risk persons in year 1, and in 8.2 of 1000 healthy and 29.3 of 1000 high-risk persons in year 2. After adjustments, vaccination was associated with a 48% reduction in the incidence of hospitalization or death (95% confidence interval [CI], 42-52) in year 1 and 31% (95% CI, 26-37) in year 2. Effectiveness estimates were statistically significant and generally consistent across the healthy and high-risk subgroups. The absolute risk reduction, however, was 2.4- to 4.7-fold higher among high-risk than among healthy elderly persons. All elderly individuals may substantially benefit from vaccination. However, the impact of influenza is greater in persons with high-risk medical conditions.
authors.affiliation: HealthPartners Research Foundation, Bloomington, IN, USA.
authors.forename: Eelko
authors.initials: E
authors.lastname: Hak
authors.forename: James
authors.initials: J
authors.lastname: Nordin
authors.forename: Feifei
authors.initials: F
authors.lastname: Wei
authors.forename: John
authors.initials: J
authors.lastname: Mullooly
authors.forename: Sung
authors.initials: S
authors.lastname: Poblete
authors.forename: Raymond
authors.initials: R
authors.lastname: Strikas
authors.forename: Kristin L
authors.initials: KL
authors.lastname: Nichol
mesh_terms: D000368:Aged; D015331:Cohort Studies; D005260:Female; D006299:Health Services for the Aged; D006760:Hospitalization; D006801:Humans; D007252:Influenza Vaccines / Q000627:therapeutic use*; D007251:Influenza, Human / Q000517:prevention & control*; D008297:Male; D008329:Managed Care Programs; D011446:Prospective Studies; D012307:Risk Factors; D016896:Treatment Outcome
chemical_list: D007252:Influenza Vaccines