Influenza Vaccination in Adolescents With High-Risk Conditions

OBJECTIVES. We assessed influenza vaccination rates from 1992 to 2002, individual continuity of vaccination, and missed opportunities for vaccination in adolescents with high-risk conditions. METHODS. We performed a retrospective observational study of 18 703 adolescents with high-risk conditions who were enrolled in a large health maintenance organization and received care at a multisite practice for >= 1 influenza season and the preceding year, between 1992 and 2002, was performed. Subjects were identified as having a high-risk condition if they had >= 1 visit with an associated International Classification of Diseases, Ninth Revision, Clinical Modification code during the season or previous year. Influenza vaccination rates were compared by season in logistic regression analyses, using generalized estimating equations for repeated measurements of subjects enrolled for multiple seasons. Vaccination continuity was measured for adolescents who were enrolled for 4 consecutive seasons (1999-2002) as the number of seasons during which vaccine was received. Missed opportunities were defined as visits during the first 4 months of influenza season at which an unvaccinated adolescent did not receive vaccine. RESULTS. For adolescents with high-risk conditions, influenza vaccination rates varied from 8.3% to 15.4%. Rates improved significantly from 1992 to 1993, from 8.3% to 12.8%, and again in 2001, reaching 15.4%. Only 11.1% of those enrolled continuously from 1999 to 2002 received vaccine during all 4 seasons. According to season from 1992 to 2002, 45.7% to 53.6% of unvaccinated subjects had >= 1 missed opportunity. CONCLUSIONS. Influenza vaccination rates in adolescents with high-risk conditions improved from 1992 to 2002 but were still low in recent years. Individual vaccination continuity was poor. Numerous opportunities already exist for improving coverage.