Influenza Vaccination Status of Persons Aged 65-79 Years -- Allegheny County, Pennsylvania, February-March 1997

Because influenza disproportionately affects persons aged greater than or equal to 65 years and persons who have chronic medical conditions, the Advisory Committee on Immunization Practices recommends annual influenza vaccination for persons in this age group and for all adults who have conditions that increase their likelihood of serious outcomes of influenza (1). Although no local surveys exist that routinely provide direct estimates of influenza vaccine use at the county level, Medicare claims for the 1996-97 influenza season indicated that 36% of Allegheny County, Pennsylvania (1990 population: 184,449), Medicare beneficiaries aged greater than or equal to 65 years had Medicare claims submitted for reimbursement for influenza vaccine (2). However, other Medicare beneficiaries may receive influenza vaccine but do not have claims filed for reimbursement. To estimate the prevalence of influenza vaccination, assess barriers to influenza vaccine use in the county, and to evaluate Medicare claims as a measure of vaccination use, the Allegheny County Health Department (ACHD) conducted a telephone survey of residents aged 65-79 years during February-March 1997. This report summarizes the findings from this survey, which indicate that 75% of adults in this age group reported receiving influenza vaccination during the 1996-97 influenza season, primarily in physician's offices, in comparison with the 36% of Medicare claims submitted.

A stratified, random sample of 500 residents aged 65-79 years was obtained from the 1994 voter registration list for Allegheny County. The list provided data on age, sex, race/ethnicity, and address but did not include household telephone numbers. A sample size of 128 persons was estimated to provide 80% power and a 5% level of significance for detecting a difference of 20 percentage points between Medicare claims data for the 1996-97 influenza season and self-reported vaccine use among residents aged greater than or equal to 65 years. The racial/ethnic distribution was 70% white and 30% all other racial/ethnic groups *, compared with distribution in Allegheny County of 85% white and 15% other, respectively. Men and women were sampled equally within each racial/ethnic category, resulting in an overrepresentation of men relative to the actual sex ratio in the county (1.3:1.0, women to men).

In February 1997, ACHD mailed a letter to the 500 residents describing the survey and inviting their participation; 105 (21%) persons declined participation by returning the postcard with the letter. Telephone numbers were available for 279 (71%) of the remaining 395 potential participants; of these, 244 (87%) completed interviews. The overall response rate was 49%. Average age of participants was 71 years (range: 65-79 years). Most respondents were non-Hispanic whites (75%); 57% were men. Respondents were asked about vaccination status for the 1996-97 influenza season, source of influenza vaccination, and if applicable, reason for not being vaccinated.

Logistic regression analysis, used to assess effects of age, sex, race/ethnicity, and geographic location of respondents, indicated that only whites were independently associated with vaccination (odds ratio {OR}=1.8; 95% confidence interval {CI}=1.2-2.6). Of the 244 survey participants, 176 (72% {95% CI=66%-78%}) reported being vaccinated during the 1996-97 influenza season. Influenza vaccine use was higher for non-Hispanic whites (77% {95% CI=71%-83%}) than for other racial/ethnic groups (57% {95% CI=44%-69%}) (chi square=8.5; pless than 0.001).

Among the 176 vaccinated participants, the most commonly reported sources of vaccination were physicians' offices (50%), health-care centers (29%), and shopping malls or other locations (21%). Persons of other racial/ethnic groups were more likely than whites to visit personal physicians (62% {95% CI=45%-78%} versus 48% {95% CI=40%-56%}; OR=1.8; {95% CI=0.8-4.1}) and less likely to go to shopping malls and other public places for vaccination.

Among the 68 nonvaccinated participants, the most commonly reported reasons for not being vaccinated during the 1996-97 influenza season were "no specific reason" (35%), illness after vaccination for a previous influenza season (23%), failure of physicians to recommend vaccination (15%), lack of previous influenza vaccination (15%), lack of transportation (9%), and belief that vaccination would not prevent influenza (3%). For men, the most frequent response for not being vaccinated was "no specific reason" (47% {95% CI=32%-63%}); for women, the most frequent response was not being vaccinated previously (23% {95% CI=8%-38%}). Other racial/ethnic groups reported "doctor did not recommend" as the reason for not being vaccinated more often than whites (19% {95% CI=4%-34%} versus 10% {95% CI=1%-18%}).

Weighted age-, racial/ethnic-, and sex-specific estimates of vaccine use from this survey were extrapolated to the county population (Table_1). The resulting estimate of 75% (95% CI=70%-80%) for residents aged greater than or equal to 65 years in Allegheny County reflected the racial/ethnic composition of the county and the higher vaccine use among white men and women. This estimate was more than double the 36% influenza vaccine use estimates for the 1996-97 influenza season from Medicare claims.

Reported by: B Dixon, MD, F Ruben, MD, J McMahon, MPH, DL Hennon, Div of Infectious Diseases, Allegheny County Health Dept, Allegheny County; LL Gibson, MPH, EO Talbott, DrPH, RR Rycheck, MD, KE Remsberg, MSPH, LH Kuller, MD, R Engberg, Dept of Epidemiology, Graduate School of Public Health, Univ of Pittsburgh, Pittsburgh; JT Rankin, Jr, DVM, State Epidemiologist, Pennsylvania Dept of Health. Adult Vaccine-Preventable Diseases Br, Epidemiology and Surveillance Div, National Immunization Program, CDC.

Editorial Note

Editorial Note: The findings in this report suggest a relatively high influenza vaccine use (75%) among residents aged 65-79 years in Allegheny County. This estimate was substantially higher than 1995 national (58%) and 1997 Pennsylvania (66%) state-specific estimates provided by the National Health Interview Survey (NHIS) (CDC, unpublished data, 1998) and the Behavioral Risk Factor Surveillance System (BRFSS), respectively, and more than double Medicare estimates (2,3).

Possible reasons for the discrepancy between BRFSS, NHIS, and the findings in this report include 1) recent increases in coverage between survey years and 2) variability in local areas not captured in state or national surveys. The discrepancy between the responses of participants and the Medicare reimbursement claims summary may be attributed to limitations inherent in the claims summary. Sources of these limitations may be an insufficient number of claims filed by physicians in Allegheny County for influenza vaccinations and an increased enrollment of Medicare beneficiaries in managed-care organizations, which do not report vaccination data to the Health Care Financing Administration. However, because less than 21% of residents aged greater than or equal to 65 years in Allegheny County were members of a managed-care organization in 1996 (4), the low vaccination claims probably were not caused by enrollment of Medicare beneficiaries in managed-care organizations.

The racial/ethnic disparity in vaccination levels among residents aged greater than or equal to 65 years in Allegheny County was consistent with previously reported data (5,6). Reasons cited by survey participants for not being vaccinated also were consistent with previous reports, which indicated that lack of knowledge, misconceptions about vaccine-associated illnesses, and lack of recommendation from physicians are primary reasons for not being vaccinated against influenza (7,8).

The findings in this report are subject to at least four limitations. First, the results of this survey are based on responses from only 244 older voters in Allegheny County. Those who did not participate were more likely than those who participated to be white women. Second, the findings are based on self-reports not verified by a review of medical records. Third, vaccination status of nonparticipants was unknown. Finally, the results may be overestimated because the survey included only households with telephones.

The high proportion of residents reporting physicians as their source of vaccination and the 15% of residents reporting lack of physician's recommendation as a reason for not being vaccinated underscore the influence of physicians on influenza vaccine use. Academic institutions (e.g., schools of medicine and schools of public health) could provide physician training through continued medical-education sessions that focus on reducing missed opportunities for vaccination and using a patient reminder system. Countywide provider and public educational and promotional campaigns can help dispel concerns about influenza vaccination and improve acceptance of the vaccine by older adults.

References

1. CDC. Prevention and control of influenza -- recommendations of the Advisory Committee on Immunization Practices. MMWR 1997;46(no. RR-9).

2. Health Care Financing Administration. Influenza immunizations paid for by Medicare: state and county rates. Washington, DC: US Department of Health and Human Services, Health Care Financing Administration, October 1996.

3. CDC. Influenza and pneumococcal vaccination levels among adults aged greater than or equal to 65 years -- United States, 1997. MMWR 1998;47: 797-802.

4. Health Care Financing Administration. Medicare managed care market penetration for all Medicare plan contractors -- quarterly state/county/plan data files. Available at: http://www.hcfa.gov/medicare/mpscpt1.htm. Accessed June 1998.

5. CDC. Race-specific differences in influenza vaccination levels among Medicare beneficiaries -- United States, 1994. MMWR 1995;44:7-31.

6. CDC. Influenza vaccination coverage levels in selected sites -- United States, 1989. MMWR 1990; 39:10-160,165-7.

7. CDC. Adult immunization: knowledge, attitudes, and practices -- DeKalb and Fulton counties, Georgia. MMWR 1988;37:657-61.

8. Williams WW, Hickson MA, Kane MA, Kendal AP, Spika JS, Hinman AR. Immunization policies and vaccine coverage among adults: the risk for missed opportunities. Ann Intern Med 1988; 108:616-25.

Blacks were combined with other races in this analysis because their numbers were too small for separate analysis.

TABLE 1. Influenza vaccination status of persons aged 65-79 years, by sex, race, and
age -- Allegheny County, Pennsylvania, 1996-97 influenza season
===============================================================================================
                                                  Vaccinated persons
                                                ----------------------
Race/Sex/              County        No.
 Age group (yrs)   population   participants    No.    (%)   (95% CI*)
----------------------------------------------------------------------
White men
  65-70                30,350         39         28   (72)   (58%-86%)
  71-79                39,237         63         53   (84)   (75%-93%)

White women
  65-70                38,291         34         29   (85)   (73%-97%)
  71-79                62,615         48         32   (67)   (54%-80%)

Other men+
  65-70                 2,567         11          6   (55)   (26%-84%)
  71-79                 2,823         26         14   (54)   (35%-73%)

Other women+
  65-70                 3,207          6          3   (50)   (10%-90%)
  71-79                 5,359         17         11   (65)   (42%-88%)

Total                 184,449        244        176   (72)   (66%-78%)
----------------------------------------------------------------------
* Confidence interval.
+ Blacks were combined with other races in this analysis because their numbers were too small
  for separate analysis.
===============================================================================================

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