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Vaccination Coverage Among Persons with Asthma — United States, 2010–2011 Influenza Season

Asthma was the most common underlying condition among persons hospitalized with pandemic influenza A (H1N1) virus infection in 2009 (1). Although persons with asthma are not more likely than others to get influenza, influenza can make asthma symptoms worse, trigger asthma attacks, and lead to pneumonia or other complications that result in hospitalization and even death.* During 1964–2010, the Advisory Committee on Immunization Practices (ACIP) recommended that all adults and children aged ≥6 months with asthma receive an influenza vaccination annually (2). Beginning with the 2010–11 influenza season, ACIP expanded its annual vaccination recommendation to include all persons aged ≥6 months, while emphasizing that protection of persons at higher risk for influenza-related complications continue as a focus of vaccination efforts (2). To provide the first update of national vaccination coverage among persons aged ≥2 years with asthma since the new ACIP recommendation, CDC analyzed data from the 2010 and 2011 National Health Interview Survey (NHIS). This report describes the results of that analysis, which indicated that influenza vaccination during the 2010–11 season among persons with asthma was 50%, up from 36% 5 years earlier (3). However, vaccination coverage across all age groups, including among those with health insurance, a usual place for health care, and one or more health-care visits in the past 12 months, remained well below Healthy People 2020 targets† of 80% for children aged 6 months–17 years and 90% for adults aged ≥18 years who are at high risk. These findings highlight the need to educate health-care providers and persons with asthma about the importance of annual influenza vaccination.

NHIS is an annual, in-person survey of the noninstitutionalized U.S. civilian population. It is based on a multistage sampling of households (4). From each family surveyed, one sample child (if present) and one sample adult are randomly selected, and information about receipt of influenza vaccination in the previous 12 months is collected. This analysis used 2010 and 2011 NHIS data to estimate influenza vaccination coverage among persons with current asthma§ aged ≥2 years¶ during the 2010–11 influenza season. To better assess influenza vaccination coverage for the 2010–11 season, data from respondents interviewed during September–June and vaccinated during August–May were analyzed. For missing vaccination month and year, information was imputed from donor pools matched for week of interview, age group, region of residence, and race/ethnicity. The Kaplan-Meier survival analysis procedure was used.**

All analyses were conducted using statistical software to account for the complex sample design. Vaccination status was stratified by characteristics known to be associated with influenza vaccination, including age group, race/ethnicity, family income relative to family size, health insurance coverage, number of health-care visits in the past year, and having a usual place for health care (3,5,6). Weighted estimates of vaccination coverage were compared using t-tests, with statistical significance defined as p<0.05.

The response rates for the 2010 and 2011 NHISs were 79.5 and 82.0%, respectively. Responses from 32,636 persons aged ≥2 years were analyzed. Of those, 2,809 (8.6%) reported having (or were reported to have) current asthma. Vaccination coverage for the 2010–11 season among persons with current asthma was 49.6%, compared with 37.5% among those without current asthma (p<0.05) (Table 1). Among persons with current asthma, those aged 50–64 years and ≥65 years had the highest vaccination coverage (61.7% and 76.5%, respectively). For all age groups, a higher proportion of persons with current asthma received influenza vaccination than did those without current asthma (p<0.05) (Table 1). Vaccination coverage among persons with asthma who experienced an asthma attack in the preceding 12 months did not differ significantly from the coverage of persons with asthma who did not have an asthma attack or an emergency department (ED)/urgent care visit in the preceding 12 months. Vaccination coverage was also similar among persons with asthma who had an ED/urgent care visit in the preceding 12 months to the coverage of persons with asthma who did not have an asthma attack or ED/urgent care visit in the preceding 12 months.

For all persons, vaccination coverage increased as the number of health-care visits over the past year increased, and coverage was significantly lower among those with no health-care visits in the past year (Table 2). Except for persons who had six to nine health-care visits and for persons who had no usual place for health care, influenza vaccination was significantly higher among persons with current asthma than it was for those without current asthma across all other characteristics, including number of health-care visits in the past 12 months, racial/ethnic group, having a usual place for health care, ability to pay for prescription drugs, and family income adjusted for family size (Table 2).

Among all persons, more than twice as many persons with health insurance coverage were vaccinated compared with those without health insurance coverage. Similarly, vaccination coverage was more than double among persons with a usual place for health care than among persons without a usual place for care (Table 2). Among persons with current asthma, 52.0% of those with a usual place for care were vaccinated, compared with 19.2% of those without a usual place for care (p<0.05). Regardless of asthma status, vaccination coverage was significantly lower among those who could not afford prescription drugs during the past 12 months than for those who could (Table 2).

Within the "all persons" and "without current asthma" groups, vaccination coverage for persons in families with incomes ≥250% the poverty threshold for family size was significantly higher than it was for persons in families with incomes less than the poverty threshold for family size. In addition, within the "all persons" and "without current asthma" groups, vaccination coverage was lower among non-Hispanic blacks and Hispanics than among non-Hispanic whites (Table 2). Among persons with current asthma, vaccination coverage was similar across racial/ethnic and income-to-poverty threshold ratio groups.

Reported by

Michael E. King, PhD, Div of Environmental Hazards and Health Effects, National Center for Environmental Health; Peng-jun Lu, MD, PhD, Alissa O'Halloran, MSPH, Helen Ding, MD, Immunization Svcs Div, National Center for Immunization and Respiratory Diseases; Matthew J. Lozier, PhD, EIS Officer, CDC. Corresponding contributor: Matthew J. Lozier, mlozier@cdc.gov, 770-488-0794.

Editorial Note

This report provides the first update of influenza vaccination coverage among the noninstitutionalized U.S. civilian population of persons with current asthma since ACIP recommended annual influenza vaccination for all persons aged ≥6 months beginning with the 2010–11 influenza season. Vaccination coverage among persons with current asthma has increased from 36% during the 2005–06 influenza season†† (3) to 50% during the 2010–11 season, with coverage increasing for all age groups.

This analysis supports findings from previous studies using NHIS data (3,6) indicating that having more health-care visits, health insurance coverage, a usual place for health care, and a higher family income relative to family size are significantly associated with higher vaccination coverage. Despite increased vaccination coverage among those with more health-care visits over the past year, more than half of persons with current asthma lacked current vaccination, suggesting that many health-care visits are missed opportunities for influenza-related education and vaccination.

ACIP has incrementally expanded the populations in the United States for whom seasonal influenza vaccination is recommended. Although children with asthma have been recommended to receive influenza vaccination annually, ACIP first recommended vaccination for all children aged 24–59 months regardless of risk status for the 2006–07 influenza season, and ACIP expanded that recommendation to include all children aged 5–18 years for the 2008–09 influenza season (7,8).§§ For the 2010–11 influenza season, ACIP recommended seasonal influenza vaccination for all persons aged ≥6 months (2). Although influenza vaccination coverage among persons with current asthma increased from 36.0% in 2005–06 to 49.6% in 2010–11, coverage among persons with current asthma increased the most among children aged 2–17 years (a 20.3 percentage point increase, from 32.5% to 52.8%). A similar increase was observed over the same period among children aged 2–17 years without current asthma (a 22.9 percentage point increase, from 15.9% to 38.8%). The increase suggests that the 2006 and 2008–2009 ACIP recommendations indicating vaccination of children regardless of risk status might have raised awareness about the importance of annual influenza vaccination among all children. Another possible contributing factor is that the 2009 H1N1 pandemic led to increased coverage during the 2010–11 influenza season.

The findings in this report are subject to at least five limitations. First, the limited sample size of persons with current asthma (n = 2,809) prevented reliable estimation of vaccination coverage of other sociodemographic subgroups not examined in this analysis. Second, because NHIS includes only those in the noninstitutionalized U.S. civilian population who agreed to participate, results might not be representative of other populations. Third, the NHIS response rates of 79.5% and 82.0% might have resulted in nonresponse bias, even after adjustment for nonresponse. Fourth, ACIP recommends that children aged 6 months–8 years who have never been vaccinated for influenza receive two vaccinations during the first influenza season to optimize immune response, but this analysis could not determine vaccination status from previous years (2). Finally, determination of asthma status and vaccination status in NHIS is made by self-report, which introduces the possibility of recall bias and misclassification (9).

These findings highlight the need to increase awareness of the importance of seasonal influenza vaccination for persons with asthma. The findings support recommendations made by the Task Force on Community Preventive Services, which recommends multicomponent interventions aimed at increasing influenza vaccination coverage (10). Specifically, the task force recommends the combination of one or more interventions to enhance access to vaccination services (e.g., reduced client out-of-pocket costs) with at least one provider-based or system-based intervention (e.g., provider reminder systems), and/or at least one intervention to increase client demand for vaccination (e.g., client reminders). In addition, to be consistent with ACIP recommendations, asthma education for health-care professionals could include recommendations for influenza vaccination for all patients with current asthma.

Acknowledgments

James A. Singleton, Walter W. Williams, National Center for Immunization and Respiratory Diseases; Dana Flanders, National Center for Environmental Health, CDC.

References

What is already known on this topic? Although persons with asthma historically have had higher influenza vaccination coverage than persons without asthma, coverage remains lower than Healthy People 2020 targets. What is added by this report? Analysis of 2010 and 2011 National Health Interview Survey data shows that influenza vaccine coverage during the 2010–11 season among persons with asthma was 50%, up from 36% during the 2005–06 season, but coverage across all age groups remained well below Healthy People 2020 targets of 80% for children aged 6 months–17 years and 90% for adults aged ≥18 years who are at high risk. What are the implications for public health practice? Measures that increase influenza vaccination among persons with asthma should be implemented. Interventions that have demonstrated benefits in similar settings include client reminders, reduced client out-of-pocket costs, and provider reminder systems.

TABLE 1. Influenza vaccination coverage* among persons aged ≥2 years, by current asthma status† and age group§ — National Health Interview Survey (NHIS), United States, 2010–11 influenza season Age group (yrs) All persons Without current asthma With current asthma No.¶ % (95% CI) No. % (95% CI) No. % (95% CI) 2–17 6,900 40.2 (38.4–42.1) 6,186 38.8 (37.0–40.8) 714 52.8** (47.3–58.6) 18–49 14,208 26.1†† (25.0–27.2) 13,118 25.4†† (24.3–26.5) 1,090 34.6**†† (30.7–38.8) 50–64 6,218 43.7†† (42.1–45.4) 5,652 42.0†† (40.4–43.7) 566 61.7**†† (55.8–67.7) ≥65 5,310 70.2†† (68.2–72.1) 4,871 69.7†† (67.7–71.7) 439 76.5**†† (70.2–82.2) Total 32,636 38.5 (37.7–39.4) 29,827 37.5 (36.6–38.4) 2,809 49.6** (47.0–52.3)

TABLE 1. (Continued) Influenza vaccination coverage* among persons aged ≥2 years, by current asthma status† and age group§ — National Health Interview Survey (NHIS), United States, 2010–11 influenza season Age group (yrs) With asthma and attack in past 12 mos With asthma and ED/urgent care

visit in past 12 mos With asthma and no attack or ED/urgent care visit in past 12 mos No. % (95% CI) No. % (95% CI) No. % (95% CI) 2–17 268 49.0 (40.9–57.7) 118 50.6 (37.8–65.0) 328 57.1 (49.0–65.5) 18–49 415 37.3†† (30.8–44.7) 118 35.2 (24.4–48.9) 557 32.4†† (26.9–38.8) 50–64 240 59.6 (50.0–69.3) 74 62.6 (46.7–78.5) 252 63.4 (55.1–71.7) ≥65 133 74.3†† (63.2–84.3) 50 83.7†† (68.9–94.1) 256 75.8†† (67.4–83.3) Total 1,056 48.5 (44.3–52.8) 360 51.3 (44.3–58.7) 1,393 50.2 (46.3–54.2)