Influenza Vaccination Coverage Levels

Continued annual monitoring is needed to determine the effects on vaccination coverage of vaccine supply delays and shortages, changes in influenza vaccination recommendations and target groups for vaccination, reimbursement rates for vaccine and vaccine administration, and other factors related to vaccination coverage among adults and children. One of the Healthy People 2010 objectives (objective no. 14-29a) includes achieving an influenza vaccination coverage level of 90% for persons aged 65 years and older and among nursing home residents; new strategies to improve coverage are needed to achieve this objective. Increasing vaccination coverage among persons who have high-risk conditions and are aged <65 years, including children at high risk, is the highest priority for expanding influenza vaccine use.

On the basis of the 2007 final data and the 2008 early release data from the National Health Interview Survey (NHIS), estimated national influenza vaccine coverage during the 2006--07 and 2007--08 influenza seasons increased minimally among persons aged 65 years and older and those aged 50--64 years (Table 3) and are only slightly lower than coverage levels observed before the 2004--05 vaccine shortage year. In the 2006--07 and 2007--08 influenza seasons, estimated vaccination coverage levels among adults with high-risk conditions aged 18--49 years were 25% and 30%, respectively, substantially lower than the Healthy People 2000 and Healthy People 2010 objectives of 60% (Table 3)

Studies conducted among children and adults indicate that opportunities to vaccinate persons at risk for influenza complications (e.g., during hospitalizations for other causes) often are missed. In one study, 23% of children hospitalized with influenza and a comorbidity had a previous hospitalization during the preceding influenza vaccination season. In a study of hospitalized Medicare patients, only 31.6% were vaccinated before admission, 1.9% during admission, and 10.6% after admission. A study in New York City conducted during 2001--2005 among 7,063 children aged 6--23 months indicated that 2-dose vaccine coverage increased from 1.6% to 23.7% over time; however, although the average number of medical visits during which an opportunity to be vaccinated decreased during the course of the study from 2.9 to 2.0 per child, 55% of all visits during the final year of the study still represented a missed vaccination opportunity. Using standing orders in hospitals increases vaccination rates among hospitalized persons, and vaccination of hospitalized patients is safe and stimulates an appropriate immune response. In one survey, the strongest predictor of receiving vaccination was the survey respondent's belief that he or she was in a high-risk group, based on data from one survey; however, many persons in high-risk groups did not know that they were in a group recommended for vaccination.

Reducing racial/ethnic health disparities, including disparities in influenza vaccination coverage, is an overarching national goal that is not being met. Estimated vaccination coverage levels in 2007 among persons aged 65 years and older were 70% for non-Hispanic whites, 58% for non-Hispanic blacks, and 54% for Hispanics. Among Medicare beneficiaries, other key factors that contribute to disparities in coverage include variations in the propensity of patients to actively seek vaccination and variations in the likelihood that providers recommend vaccination. One study estimated that eliminating these disparities in vaccination coverage would have an impact on mortality similar to the impact of eliminating deaths attributable to kidney disease among blacks or liver disease among Hispanics.

Reported vaccination levels are low among children at increased risk for influenza complications. Coverage among children aged 2--17 years with asthma for the 2004--05 influenza season was estimated to be 29%. One study reported 79% vaccination coverage among children attending a cystic fibrosis treatment center. During the first season for which ACIP recommended that all children aged 6 months--23 months receive vaccination, 33% received 1 or more doses of influenza vaccine, and 18% received 2 doses if they were unvaccinated previously. Among children enrolled in HMOs who had received a first dose during 2001--2004, second dose coverage varied from 29% to 44% among children aged 6--23 months and from 12% to 24% among children aged 2--8 years. A rapid analysis of influenza vaccination coverage levels among members of an HMO in Northern California demonstrated that during the 2004--05 influenza season, the first year of the recommendation for vaccination of children aged 6--23 months, 1-dose coverage was 57%. During the 2006--07 influenza season, the second season for which ACIP recommended that all children aged 6 months--23 months receive vaccination, coverage remained low and did not increase substantially from the 2004--05 season. Data collected in 2007 by the National Immunization Survey indicated that for the 2006--07 season, 32% of children aged 6--23 months received at least 1 dose of influenza vaccine and 21% were fully vaccinated (i.e., received 1 or 2 doses depending on previous vaccination history); however, results varied substantially among states. As has been reported for older adults, a physician recommendation for vaccination and the perception that having a child be vaccinated "is a smart idea" were associated positively with likelihood of vaccination of children aged 6--23 months. Similarly, children with asthma were more likely to be vaccinated if their parents recalled a physician recommendation to be vaccinated or believed that the vaccine worked well. Implementation of a reminder/recall system in a pediatric clinic increased the percentage of children with asthma receiving vaccination from 5% to 32%.

Although annual vaccination is recommended for HCP and is a high priority for reducing morbidity associated with influenza in health-care settings and for expanding influenza vaccine use, national survey data demonstrated a vaccination coverage level of only 42% among HCP during the 2005--06 season, and 44% during the 2006--07 season (Table 3). Vaccination of HCP has been associated with reduced work absenteeism and with fewer deaths among nursing home patients and elderly hospitalized patients. Factors associated with a higher rate of influenza vaccination among HCP include older age, being a hospital employee, having employer-provided health-care insurance, having had pneumococcal or hepatitis B vaccination in the past, or having visited a health-care professional during the preceding year. Non-Hispanic black HCP were less likely than non-Hispanic white HCP to be vaccinated. HCP who decline vaccination frequently express doubts about the risk for influenza and the need for vaccination, are concerned about vaccine effectiveness and side effects, and dislike injections.

Vaccine coverage among pregnant women increased during the 2007--08 influenza season with 24% of pregnant women reporting vaccination, excluding pregnant women who reported diabetes, heart disease, lung disease, and other selected high-risk conditions (Table 3). However, the sample size is small, and the increase in coverage compared with previous seasons was not statistically significant. In a study of influenza vaccine acceptance by pregnant women, 71% of those who were offered the vaccine chose to be vaccinated. However, a 1999 survey of obstetricians and gynecologists determined that only 39% administered influenza vaccine to obstetric patients in their practices, although 86% agreed that pregnant women's risk for influenza-related morbidity and mortality increases during the last two trimesters.

Influenza vaccination coverage in all groups recommended for vaccination remains suboptimal. Despite the timing of the peak of influenza disease, administration of vaccine decreases substantially after November. According to results from the NHIS regarding the two most recent influenza seasons for which these data are available, approximately 84% of all influenza vaccination were administered during September--November. Among persons aged 65 years and older, the percentage of September--November vaccinations was 92%. Because many persons recommended for vaccination remain unvaccinated at the end of November, CDC encourages public health partners and health-care providers to conduct vaccination clinics and other activities that promote seasonal influenza vaccination annually during National Influenza Vaccination Week (December 6--12, 2009) and throughout the remainder of the influenza season.

Self-report of influenza vaccination among adults compared with determining vaccination status from the medical record, is a sensitive and specific source of information. Patient self-reports should be accepted as evidence of influenza vaccination in clinical practice. However, information on the validity of parents' reports of pediatric influenza vaccination is not yet available.

TABLE 3. Influenza vaccination* coverage levels for the 2005--06, 2006--07, and 2007-08 influenza seasons, by population group --- National Health Interview Survey (NHIS), United States, 2006, 2007, and 2008, and National Immunization Survey (NIS), 2006 and 2007

Population group	2005–06 season			2006–07 season			2007–08 season
	Crude sample size†	Influenza vaccination level		Crude sample size	Influenza vaccination level		Crude sample size	Influenza vaccination level
	Crude sample size†	%	(Cl §)	Crude sample size	%	(Cl)	Crude sample size	%	(Cl)
Persons with an age indication
Aged 6-23 mos (NIS¶)	13,546	32.2	(30.9–33.5)	9,710	31.8	(30.2–33.4)	NA**
Aged 2–4 yrs	611	26.4	(22.2–31.0)	636	39.2	(34.9--43.6)	674	40.3	(35.8–45.0)
Aged 50–64 yrs	2,843	31.6	(29.5–33.8)	2,787	37.1	(34.8–39.5)	3,258	38.4	(36.4–40.4)
Aged 65 yrs and older	2,328	64.5	(62.6–66.8)	2,260	66.0	(63.7–68.3)	2,658	66.3	(64.2–68.3)
Persons with high-risk conditions††
Aged 5–17 yrs	376	22.1	(17.1–28.2)	283	28.0	(20.0–37.1)	262	36.2	(29.3–43.6)
Aged 18–49 yrs	937	23.4	(20.2–26.9)	883	25.3	(21.8--29.3)	1,049	30.4	(27.1–34.0)
Aged 50–64 yrs	878	44.3	(40.2–48.5)	824	47.8	(43.4–52.1)	1,001	48.4	(44.7–52.2)
Aged 18–64 yrs	1,815	33.4	(30.5–36.5)	2,303	35.8	(33.0--38.8)	2,050	38.8	(36.2–41.4)
Persons without high-risk conditions
Aged 5–17 yrs	2,679	12.4	(10.9–14.1)	2,570	17.3	(15.4–19.2)	2,925	21.1	(19.3–23.1)
Aged 18–49 yrs	6,275	13.4	(12.4–14.6)	5.844	15.3	(14.2–16.6)	6,467	17.0	(15.7–18.3)
Aged 50–64 yrs	1,956	26.0	(23.7–28.4)	1,956	32.7	(30.3--35.2)	2,248	34.1	(31.7–36.6)
Pregnant women§§	126	12.3	(7.2–20.4)	123	14.7	(8.9–23.2)	113	24.2	(15.1–36.6)
Health-care workers¶¶	833	41.8	(37.4–6.3)	850	44.4	(40.2–48.7)	NA
Household contacts of persons at high risk, including children aged <5 yrs***
Aged 5–17 yrs	840	16.3	(13.4–19.7)	741	26.0	(21.5–31.1)	968	24.8	(21.4–28.6)
Aged 18–49 yrs	1621	14.4	(12.5–16.5)	1,349	17.0	(15.0–19.4)	1,753	19.5	(17.1–22.1)
* Answered yes to this question, "During the past 12 months, have you had a flu shot (flu spray)," and answered the follow-up question "What was the month and year of your most recent shot (spray)." Questions were asked during a face-to-face interview conducted any day during March through August in the respective study year. † The population sizes by sub groups can be found at http://www.cdc.gov/flu/professionals/vaccination/pdf/influenza_vaccine_ target_populations.pdf. §95% confidence interval. ¶ NIS uses provider-verified vaccination status to improve the accuracy of the estimate. The NIS estimate for the 2007--08 season will be available fall 2009 The NHIS coverage estimates based on parental report were 39.5% (CI = 32.8--46.7, n = 295) for the 2005--06 season, 48.0% (CI = 40.2--55.9; n = 368) for the 2006--07 season, and 49.1% (CI = 41.9--56.4) for the 2007--08 season. Data not yet available. †† Adults categorized as being at high risk for influenza-related complications self-reported one or more of the following: 1) ever being told by a physician they had diabetes, emphysema, coronary heart disease, angina, heart attack, or other heart condition; 2) having a diagnosis of cancer during the previous 12 months (excluding nonmelanoma skin cancer) or ever being told by a physician they have lymphoma, leukemia, or blood cancer during the previous 12 months (post coding for a cancer diagnosis was not yet completed at the time of this publication so this diagnosis was not include in the 2006--07 season data.); 3) being told by a physician they have chronic bronchitis or weak or failing kidneys; or 4) reporting an asthma episode or attack during the preceding 12 months. For children aged <18 years, high-risk conditions included ever having been told by a physician of having diabetes, cystic fibrosis, sickle cell anemia, congenital heart disease, other heart disease, or neuromuscular conditions (seizures, cerebral palsy, and muscular dystrophy), or having an asthma episode or attack during the preceding 12 months. §§ Aged 18--44 years, pregnant at the time of the survey and without high-risk conditions. Adults were classified as health-care workers if they were employed in a health-care occupation or in a health-care--industry setting, on the basis of standard occupation and industry categories recoded in groups by CDC's National Center for Health Statistics. * Interviewed sample child or adult in each household containing at least one of the following: a child aged <5 years, an adult aged 65 years and older, or any person aged 5--17 years at high risk (see previous footnote ††). To obtain information on household composition and high-risk status of household members, the sampled adult, child, and person files from NHIS were merged. Interviewed adults who were health-care workers or who had high-risk conditions were excluded. Information could not be assessed regarding high-risk status of other adults aged 18--64 years in the household; therefore, certain adults aged 18--64 years who lived with an adult aged 18--64 years at high risk were not included in the analysis. Also note that although the recommendation for children aged 2--4 years was not in place during the 2005--06 season, children aged 2--4 years in these calculations were considered to have an indication for vaccination to facilitate comparison of coverage data for subsequent years.