PCPs miss opportunities to vaccinate high-risk adolescents against influenza, researchers find

A vast majority of adolescents with high-risk medical conditions do not receive the influenza vaccination, data from a retrospective observational study suggest. Noting that influenza affects 20% to 40% of children and adolescents each year, researchers at Harvard Medical School assessed influenza vaccination rates from 1992 to 2002 among adolescents aged 11 to 17 years who had >=1 high-risk medical condition (n=18,703). The study population was drawn from patients seen at Harvard Vanguard...

A vast majority of adolescents with high-risk medical conditions do not receive the influenza vaccination, data from a retrospective observational study suggest.

Noting that influenza affects 20% to 40% of children and adolescents each year, researchers at Harvard Medical School assessed influenza vaccination rates from 1992 to 2002 among adolescents aged 11 to 17 years who had >=1 high-risk medical condition (n=18,703). The study population was drawn from patients seen at Harvard Vanguard Medical Associates, a large, multispecialty group practice composed of 14 health centers serving approximately 300,000 patients in the Boston area. All patients were also enrolled in Harvard Pilgrim Health Care, a large nonprofit health insurance plan, at the time of the study.

The children were identified as having a high-risk condition (such as asthma, immunosuppressive disorders, or diabetes) if they had >=1 office visit or hospitalization during a given season or previous year that was associated with certain diagnostic codes, which were determined based on recommendations from the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices as well as from previous studies on influenza in high-risk subjects.

The researchers determined influenza vaccination rates for each season from 1992 to 2002, individual continuity of vaccination, and missed opportunities for vaccination in adolescents with high-risk conditions. Missed opportunities were defined as visits during the first 4 months of influenza season at which an unvaccinated adolescent did not receive the influenza vaccine.

For adolescents with high-risk conditions, influenza vaccination rates varied from 8.3% to 15.4% during the study years. Rates improved significantly from 1992 to 1993, from 8.3% to 12.8%, and again in 2001, reaching 15.4%. The vaccination rate in the final (2002) season was 14.6%.

Because the greatest improvement in vaccination rates occurred between the 1992 and 1993 seasons, the researchers used the 1993 season as the reference period. After adjusting for age, sex, preventive care use, and type of high-risk condition, the researchers found the change in vaccination rate from 1992 to 1993 to be significant, with the odds of participants receiving an influenza vaccine being 47% less in 1992 (OR, 0.53; 95% CI, 0.42-0.64; P<.001). The change in vaccination rate was also significant in the 2001 season, when participants were more likely to have been vaccinated than in 1993 (OR, 1.22; 95% CI, 1.05-1.42; P=.009).

Only 11.1% of those enrolled continuously from 1999 to 2002 received vaccine during all 4 seasons. Over the course of the 11 influenza seasons, from 1992 to 2002, 45.7% to 53.6% of unvaccinated subjects had at least 1 missed opportunity.

"Influenza vaccination rates in adolescents with high-risk conditions improved from 1992 to 2002 but were still low in recent years," the authors concluded. "Individual vaccination continuity was poor. Numerous opportunities already exist for improving coverage." (Nakarmura MM and Lee GM. Pediatrics 2008;122:920-928.)