Influenza Vaccination Levels Among Persons Aged >65 Years and Among Persons Aged 18--64 Years with High-Risk Conditions --- United States, 2003

Influenza vaccination is an effective tool for preventing hospitalization and death among persons aged >65 years and among persons aged 18--64 years with medical conditions that increase the risk for influenza-related complications (1). Two national health objectives for 2010 are to increase influenza vaccination coverage to 90% among persons aged >65 years and to 60% among persons aged 18--64 years who have one or more high-risk conditions (objectives 14-29a and 14-29c, respectively) (2). To determine influenza vaccination coverage among persons in both targeted groups, CDC analyzed data from the 2003 National Health Interview Survey (NHIS). This report summarizes the results of that analysis, which determined that influenza vaccination coverage among persons aged >65 years and persons aged 18--64 years with high-risk conditions remains substantially below 2010 target levels. In addition, racial/ethnic disparities in coverage levels persist in both targeted populations. To improve overall influenza vaccination coverage and reduce racial/ethnic disparities, combinations of evidence-based effective interventions should be implemented (3), and the influenza vaccine supply should be stabilized (4).

NHIS is conducted using face-to-face interviews among the civilian, noninstitutionalized U.S. population. Questions regarding influenza vaccination are part of the sample adult core questionnaire, which collects information regarding the health of one randomly selected adult in each family. All respondents were asked, "During the past 12 months, have you had a flu shot?" In 1994, only half-year data were available. In 1990, 1992, and 1996, influenza vaccination questions were not included in the questionnaire. Therefore, midpoint values between the preceding and following years were used to estimate coverage in those years. Before 1997, vaccination coverage among persons by high-risk group could not be assessed for purpose of comparison because the questionnaire was redesigned in 1997 and information on health conditions was not collected in the same manner.

NHIS data for 2003 were analyzed to estimate influenza vaccination coverage in the targeted populations by race/ethnicity and sociodemographic characteristics, including access to health care. Trends in annual estimates during 1989--2003 were evaluated. Final response rates for the adult core sample during 1997--2003 ranged from 69.6% to 80.4%; the response rate in 2003 was 74.2%. Only non-Hispanic whites, non-Hispanic blacks, and Hispanics were included in the analysis for 2003, totaling 5,538 adults aged >65 years and 4,238 adults aged 18--64 years with high-risk conditions. Samples were weighted to produce national estimates. Univariate analysis was conducted using statistical software to account for the complex survey design. Associations between coverage levels and characteristics were measured using 95% confidence intervals. Persons with high-risk conditions had one or more of the following: ever being told by a physician they had diabetes, emphysema, coronary heart disease, angina, heart attack, or other heart condition; receiving a diagnosis of cancer during the preceding 12 months (excluding nonmelanoma skin cancer) or ever being told by a physician they had lymphoma, leukemia, or blood cancer; being told by a physician during the preceding 12 months they had chronic bronchitis or weak or failing kidneys; or having an asthma episode or attack during the preceding 12 months.

In 2003, influenza vaccination levels varied by age group, race/ethnicity, presence of high-risk medical conditions, and other characteristics. coverage among persons aged >65 years was 65.6%. Racial/ethnic--specific estimates of coverage were 68.7% for non-Hispanic whites, 48.0% for non-Hispanic blacks, and 45.4% for Hispanics (Table 1). Combining the three racial/ethnic populations, the following characteristics were associated with lower coverage levels: age 65--74 years, less than a high school education, income below the poverty threshold, no supplemental health insurance, no high-risk conditions, and fewer doctor visits in the preceding 12 months. Among persons aged 18--64 years with high-risk conditions, influenza vaccination coverage was 34.1% (Table 2). Racial/ethnic--specific estimates of coverage among persons aged 18--64 years with high-risk conditions were 35.8% for non-Hispanic whites, 30.4% for non-Hispanic blacks, and 27.0% for Hispanics. Characteristics associated with lower coverage levels in the combined racial/ethnic groups were age 18--49 years, less than high school education, income near (100%--199%) or below (<100%) the poverty threshold, no health insurance, and fewer doctor visits during the preceding 12 months. Among Hispanics aged >18 years, those who were interviewed in Spanish had a vaccination coverage level that was nearly two thirds the level for those interviewed in English. Among persons aged 50--64 years, influenza vaccination coverage was 46.3% for persons with high-risk conditions and 32.7% for persons without high-risk conditions.

Trends over time differed by race/ethnicity and age group. During 1989--1997, among persons aged >65 years, influenza vaccination coverage among non-Hispanic whites increased from 32.1% in 1989 to 66.0% in 1997, then remained nearly stable through 2003 except for a limited decrease in 2001 (Figure). At a lower level of coverage, a similar pattern existed among non-Hispanic blacks. Among Hispanics, however, vaccination coverage declined from 55.7% in 2000 to 45.4% in 2003, and the gap in vaccination rates between Hispanics and non-Hispanic whites increased from 10.9% to 23.3% during the same period.

among all persons aged 18--64 years (with and without high-risk conditions), influenza vaccination coverage increased from 5.0% in 1989 to 22.1% in 2003, except for a limited decrease in 2001. Among persons aged 18--64 years with high-risk conditions, a similar trend was observed during 1997--2003.

Reported by: S Youngpairoj, MD, Assoc of Schools of Public Health/CDC Public Health Fellowship Program, Atlanta, Georgia. GL Euler, DrPH, PJ Lu, PhD, CB Bridges, MD, Epidemiology and Surveillance Div; PM Wortley, MD, Immunization Svcs Div, National Immunization Program, CDC.

Editorial Note:

The findings in this report indicate that influenza vaccination coverage since 2000 has increased only slightly among non-Hispanic whites and non-Hispanic blacks aged >65 years and among younger adults with high-risk conditions and decreased among Hispanics aged >65 years. Given these trends, the national health targets for influenza vaccination coverage of 90% for persons aged >65 years and 60% for persons aged 18--64 years with one or more high-risk condition will not be met by 2010. In addition, racial/ethnic disparities in coverage levels were observed, with lower coverage among non-Hispanic blacks and Hispanics than among non-Hispanic whites of both targeted populations. These disparities underscore the need to implement more widespread effective interventions (e.g., standing orders and provider and patient reminders), especially among certain racial/ethnic populations, to achieve national objectives for influenza vaccination coverage among persons aged >65 years and persons aged 18--64 years with high-risk conditions.

Multiple characteristics continue to be associated with lower influenza vaccination coverage and poor progress toward the national health objectives, including low household income, less than a high school education, less health insurance coverage, and fewer doctor visits. One study determined a stronger association between opposition to vaccination and lower influenza vaccination coverage among non-Hispanic blacks than other groups (5). low coverage might be related, in part, to how non-Hispanic blacks respond to prevention messages and guidelines (6). Among Hispanics, those who were interviewed in Spanish had lower vaccination coverage than those interviewed in English, indicating that a greater availability of Spanish-speaking health-care providers and communication materials in Spanish might help to achieve higher coverage in the Hispanic population. Among Hispanics aged >65 years, reasons for the decline in coverage, beginning in 2001, are not known; however, the decline was observed primarily among Hispanics who were interviewed in Spanish (CDC, unpublished data, 2005). Research is needed to gain insight into the causes of this pattern and reverse it.

Although a leveling of influenza vaccination coverage has been observed since 1998, the instability of the vaccine supply during recent years might have contributed to impeding progress toward the 2010 influenza vaccination targets. The decrease in coverage in 2001 likely was caused by the delayed supply of influenza vaccine during the 2000--01 influenza season (7). A less severe delay occurred during the 2001--02 season but did not result in a decrease in coverage. Progress will continue to be slowed if vaccine supply shortages such as that during the 2004--05 influenza season cannot be avoided (4). The effect of the vaccine shortage during the 2004--05 season on future demand for influenza vaccine, potentially as a result of reduced risk perception among persons who deferred vaccination, has yet to be determined. Continued surveillance for vaccination coverage is needed to assess the effects of fluctuations in available vaccine doses.

No national target for influenza vaccination coverage among persons aged 50--64 years exists; however, since 2000, the Advisory Committee on Immunization Practices (ACIP) has recommended influenza vaccination for all persons in this age group (8). Data from the 2003 NHIS indicate that coverage for persons with and without high-risk conditions in this age group remains below 50%. National health objectives for the group aged 50--64 years should be considered to help promote increased coverage.

The findings in this report are subject to at least four limitations. First, influenza vaccination status is self-reported and, therefore, subject to recall bias. However, a previous study has demonstrated that the sensitivity and specificity of self-reported influenza vaccination are high among adults (9). Second, a multivariable model was not used to adjust for potential confounding. Third, data for the 2003 NHIS are gathered from interviews conducted during the entire calendar year and primarily reflect the 2002--03 influenza season but also include vaccinations occurring in smaller portions of the preceding and subsequent seasons, reducing specificity of coverage estimates. Finally, total coverage for each age group might not be generalizable to the entire U.S. population for those age groups because only three racial/ethnic populations were included in the analysis.

To further improve vaccination coverage among adults, ACIP recommends standing orders for influenza vaccination (10). In addition, a recent systematic review by the Task Force on Community Preventive Services recommends combining interventions to increase vaccination rates, such as 1) increasing community demand for vaccinations, 2) enhancing access to vaccination services, and 3) implementing provider-based or system-based interventions (3). Other factors that might help improve influenza vaccination coverage levels among persons aged >65 years and persons aged 18--64 years with high-risk conditions include stabilizing the vaccine supply for each influenza season and developing infrastructure to vaccinate uninsured persons aged 18--64 years with high-risk conditions.

References

1. Hak E, Buskens E, van Essen GA, et al. Clinical effectiveness of influenza vaccination in persons younger than 65 years with high-risk medical conditions: the PRISMA study. Arch Intern Med 2005;165:274--80.
2. US Department of Health and Human Services. Healthy people 2010: understanding and improving health. 2nd ed. Washington, DC: US Department of Health and Human Services; 2000. Available at http://www.health.gov/healthypeople.
3. CDC. Improving influenza, pneumococcal polysaccharide, and hepatitis B vaccination coverage among adults aged <65 years at high risk: a report on recommendations of the Task Force on Community Preventive Services. MMWR 2005;54(No. RR-5).
4. CDC. Estimated influenza vaccination coverage among adults and children---United States, September 1, 2004--January 31, 2005. MMWR 2005;54:304--7.
5. Hebert PL, Frick KD, Kane RL, McBean AM. The causes of racial and ethnic differences in influenza vaccination rates among elderly Medicare beneficiaries. Health Serv Res 2005;40:517--37.
6. Witt D, Brawer R, Plumb J. Cultural factors in preventive care: African-Americans. Prim Care 2002;29:487--93.
7. CDC. Delayed supply of influenza vaccine and adjunct ACIP influenza vaccine recommendations for the 2000--01 influenza season. MMWR 2000;49:619--22.
8. CDC. Prevention and control of influenza: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 2005;54(No. RR-8):10.
9. Mac Donald R, Baken L, Nelson A, Nichol KL. Validation of self-report of influenza and pneumococcal vaccination status in elderly outpatients. Am J Prev Med 1999;16:173--7.
10. CDC. Adult immunization programs in nontraditional settings: quality standards and guidance for program evaluation---a report of the National Vaccine Advisory Committee and Use of standing orders programs to increase adult vaccination rates: recommendations of the Advisory Committee on Immunization Practices. MMWR 2000;49 (No. RR-1):15--26.

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Date last reviewed: 10/19/2005