Surveillance of Vaccination Coverage Among Adult Populations — United States, 2015

Surveillance Summaries / May 5, 2017 / 66(11);1–28

Walter W. Williams, MD1; Peng-Jun Lu, MD, PhD1; Alissa O’Halloran, MSPH1,2; David K. Kim, MD1; Lisa A. Grohskopf, MD3; Tamara Pilishvili, MPH4; Tami H. Skoff, MS4; Noele P. Nelson, MD, PhD5; Rafael Harpaz, MD6; Lauri E. Markowitz, MD6; Alfonso Rodriguez-Lainz, PhD, DVM7; Amy Parker Fiebelkorn, MSN, MPH1 (View author affiliations)

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Abstract

Problem/Condition: Overall, the prevalence of illness attributable to vaccine-preventable diseases is greater among adults than among children. Adults are recommended to receive vaccinations based on their age, underlying medical conditions, lifestyle, prior vaccinations, and other considerations. Updated vaccination recommendations from CDC are published annually in the U.S. Adult Immunization Schedule. Despite longstanding recommendations for use of many vaccines, vaccination coverage among U.S. adults is low.

Period Covered: August 2014–June 2015 (for influenza vaccination) and January–December 2015 (for pneumococcal, tetanus and diphtheria [Td] and tetanus and diphtheria with acellular pertussis [Tdap], hepatitis A, hepatitis B, herpes zoster, and human papillomavirus [HPV] vaccination).

Description of System: The National Health Interview Survey (NHIS) is a continuous, cross-sectional national household survey of the noninstitutionalized U.S. civilian population. In-person interviews are conducted throughout the year in a probability sample of households, and NHIS data are compiled and released annually. The survey objective is to monitor the health of the U.S. population and provide estimates of health indicators, health care use and access, and health-related behaviors.

Results: Compared with data from the 2014 NHIS, increases in vaccination coverage occurred for influenza vaccine among adults aged ≥19 years (a 1.6 percentage point increase compared with the 2013–14 season to 44.8%), pneumococcal vaccine among adults aged 19–64 years at increased risk for pneumococcal disease (a 2.8 percentage point increase to 23.0%), Tdap vaccine among adults aged ≥19 years and adults aged 19–64 years (a 3.1 percentage point and 3.3 percentage point increase to 23.1% and to 24.7%, respectively), herpes zoster vaccine among adults aged ≥60 years and adults aged ≥65 years (a 2.7 percentage point and 3.2 percentage point increase to 30.6% and to 34.2%, respectively), and hepatitis B vaccine among health care personnel (HCP) aged ≥19 years (a 4.1 percentage point increase to 64.7%). Herpes zoster vaccination coverage in 2015 met the Healthy People 2020 target of 30%. Aside from these modest improvements, vaccination coverage among adults in 2015 was similar to estimates from 2014. Racial/ethnic differences in coverage persisted for all seven vaccines, with higher coverage generally for whites compared with most other groups. Adults without health insurance reported receipt of influenza vaccine (all age groups), pneumococcal vaccine (adults aged 19–64 years at increased risk), Td vaccine (adults aged ≥19 years, 19–64 years, and 50–64 years), Tdap vaccine (adults aged ≥19 years and 19–64 years), hepatitis A vaccine (adults aged ≥19 years overall and among travelers), hepatitis B vaccine (adults aged ≥19 years, 19–49 years, and among travelers), herpes zoster vaccine (adults aged ≥60 years), and HPV vaccine (males and females aged 19–26 years) less often than those with health insurance. Adults who reported having a usual place for health care generally reported receipt of recommended vaccinations more often than those who did not have such a place, regardless of whether they had health insurance. Vaccination coverage was higher among adults reporting one or more physician contacts in the past year compared with those who had not visited a physician in the past year, regardless of whether they had health insurance. Even among adults who had health insurance and ≥10 physician contacts within the past year, depending on the vaccine, 18.2%–85.6% reported not having received vaccinations that were recommended either for all persons or for those with specific indications. Overall, vaccination coverage among U.S.-born adults was higher than that among foreign-born adults, with few exceptions (influenza vaccination [adults aged 19–49 years and 50–64 years], hepatitis A vaccination [adults aged ≥19 years], and hepatitis B vaccination [adults aged ≥19 years with diabetes or chronic liver conditions]).

Interpretation: Coverage for all vaccines for adults remained low but modest gains occurred in vaccination coverage for influenza (adults aged ≥19 years), pneumococcal (adults aged 19–64 years with increased risk), Tdap (adults aged ≥19 years and adults aged 19–64 years), herpes zoster (adults aged ≥60 years and ≥65 years), and hepatitis B (HCP aged ≥19 years); coverage for other vaccines and groups with vaccination indications did not improve. The 30% Healthy People 2020 target for herpes zoster vaccination was met. Racial/ethnic disparities persisted for routinely recommended adult vaccines. Missed opportunities to vaccinate remained. Although having health insurance coverage and a usual place for health care were associated with higher vaccination coverage, these factors alone were not associated with optimal adult vaccination coverage. HPV vaccination coverage for males and females has increased since CDC recommended vaccination to prevent cancers caused by HPV, but many adolescents and young adults remained unvaccinated.

Public Health Actions: Assessing factors associated with low coverage rates and disparities in vaccination is important for implementing strategies to improve vaccination coverage. Evidence-based practices that have been demonstrated to improve vaccination coverage should be used. These practices include assessment of patients’ vaccination indications by health care providers and routine recommendation and offer of needed vaccines to adults, implementation of reminder-recall systems, use of standing-order programs for vaccination, and assessment of practice-level vaccination rates with feedback to staff members. For vaccination coverage to be improved among those who reported lower coverage rates of recommended adult vaccines, efforts also are needed to identify adults who do not have a regular provider or insurance and who report fewer health care visits.

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Introduction

Overall, the prevalence of illness attributable to vaccine-preventable diseases is greater among adults aged ≥19 years than among children aged ≤12 years (1–5) attributable in great part to successful childhood vaccination programs. The prevalence of vaccine-preventable illnesses among older persons is especially high (1–4). Vaccinations are recommended throughout a person’s lifetime to prevent vaccine-preventable diseases and their sequelae. However, adult vaccination coverage remains low for most routinely recommended vaccines (5) and below Healthy People 2020 targets (https://www.healthypeople.gov/2020/topics-objectives/topic/immunization-and-infectious-diseases ). In October 2016, the Advisory Committee on Immunization Practices (ACIP) approved the adult immunization schedule for 2017 (6). Influenza vaccination is recommended for all adults each year. Other adult vaccinations are recommended for specific populations based on a person’s age, health conditions, behavioral risk factors (e.g., injection drug use), occupation, travel, and other indications (6).

In February 2016, CDC released the first comprehensive report of adult vaccination coverage that described associations related to respondents’ characteristics (e.g., demographic and access to care) (5). This surveillance summary updates those vaccination coverage estimates. The estimates provided in this report can be used by public health practitioners, adult vaccination providers, and the general public to understand better the factors that contribute to low vaccination rates and modify strategies and interventions to improve vaccination coverage.

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Methods

To assess vaccination coverage among adults aged ≥19 years for selected vaccines and factors associated with vaccination, CDC analyzed data from the 2015 National Health Interview Survey (NHIS); for influenza coverage, data from the 2014 NHIS (for August–December) also were used for the 2014 component of the 2014–15 influenza season. This report highlights the results of that analysis for influenza, pneumococcal, tetanus toxoid-containing (tetanus and diphtheria vaccine [Td] or tetanus and diphtheria with acellular pertussis vaccine [Tdap]), hepatitis A, hepatitis B, herpes zoster (shingles), and human papillomavirus (HPV). Data are reported by selected demographic and access-to-care characteristics (e.g., age, race/ethnicity, indication for vaccination, health insurance status, contacts with physicians, nativity, and citizenship). Other estimates of influenza vaccination coverage using data from 2015–16 and earlier seasons from other sources have been published (7–9). These data sources have been described previously (10). Proportions were estimated of adults aged ≥19 years who received selected vaccinations during 2010–2015. Estimates of proportions vaccinated were stratified by age group, risk status, health insurance status, having a usual place for health care, number of physician contacts, nativity, number of years living in the United States, and citizenship.

Data Source and Collection

NHIS collects information about the health and health care of the noninstitutionalized U.S. civilian population using nationally representative samples. Face-to-face interviews are conducted by the U.S. Census Bureau for CDC’s National Center for Health Statistics. The total adult sample was 33,348 persons aged ≥19 years. Additional information on NHIS methods is available at https://www.cdc.gov/nchs/nhis/methods.htm.

Questions about receipt of vaccinations recommended for adults are asked of one randomly selected adult within each family in the household and have been described previously (5). A summary is provided of questions asked to ascertain whether adults received influenza, pneumococcal, Td, Tdap, hepatitis A, hepatitis B, herpes zoster (shingles), and human papillomavirus (HPV) vaccines as well as to ascertain classification as health care personnel (HCP), whether respondents had health insurance coverage, and whether there is a place to which respondents usually go when sick or need advice on their health (Appendix). There were no questions in the 2015 NHIS to ascertain pneumococcal vaccination by type of vaccine (23-valent pneumococcal polysaccharide vaccine or 13-valent pneumococcal conjugate vaccine). The presence of selected conditions that increase risk for pneumococcal disease and are defined by ACIP as indications for pneumococcal vaccines (Box 1) (6) was determined by responses to questions in NHIS. For hepatitis A and hepatitis B vaccination, data were collected also on selected respondent characteristics that increase the risk for infection (travel to countries in which hepatitis A infections are endemic and having chronic liver disease, travel to countries in which hepatitis B infections are endemic, and having diabetes or chronic liver disease, respectively).

Vaccination status and demographic and other characteristics (e.g., health conditions, insurance status, and usual source and frequency of health care) are self-reported. Race/ethnicity was categorized as Hispanic or Latino, black, white, Asian, and “other.” Persons identified as Hispanic or Latino might be of any race. Persons identified as black, white, Asian, or other race are non-Hispanic. “Other” includes American Indians/Alaska Natives and persons of multiple race. The five racial/ethnic categories are mutually exclusive. Nativity was categorized as U.S.-born (persons born in one of the 50 states or the District of Columbia) or foreign-born (persons who were not born in the United States).

Analysis

For the noninfluenza adult vaccination coverage estimates, the weighted proportion of respondents who reported receiving selected vaccinations was calculated. To better assess influenza vaccination coverage for the 2014–15 influenza season, CDC restricted reported coverage to persons who were interviewed during August 2014–June 2015 and vaccinated during July 2014–May 2015, using the Kaplan-Meier survival analysis procedure; 2014 NHIS data for August–December 2014 were used for the 2014 component of the 2014–15 influenza season. Differences were measured as the simple difference between the 2013–14 and 2014–15 influenza seasons. Data for missing months and years of vaccination (3.5%) were imputed.

To assess adjusted vaccination coverage and adjusted prevalence ratios for each vaccine, logistic regression and predicted marginal modeling were used for selected comparisons (health insurance status). Estimates were adjusted for age, sex, race/ethnicity, marital status, education, employment status, poverty level, number of physician contacts in the past year, usual source of health care, self-reported health status, nativity, and region of residence. Income-to-poverty ratio variables are included in the NHIS public use data file (https://www.cdc.gov/nchs/nhis/nhis_2015_data_release.htm). Poverty thresholds were defined according to family size using weighted average census poverty thresholds from 2013, the average consumer price index from 2013, actual consumer price index values for January–July 2014, and projected consumer price index values for August–December 2014 (ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Dataset_Documentation/NHIS/2015/srvydesc.pdf).

Weighted data were used to produce national vaccination coverage estimates. Point estimates and 95% confidence intervals (CIs) were calculated by using statistical software to account for the complex sample design, and t tests were used for comparisons between 2015 and 2014 and for comparisons of each level of each characteristic (e.g., race/ethnicity, age group, HCP status, patient care status, access-to-care factors, nativity, years of residence in the United States, and citizenship status) to a chosen referent level (e.g., for race/ethnicity, non-Hispanic white was the reference group). For influenza vaccination, tests for linear trend were performed using a weighted linear regression on the season-specific estimates, using season number as the independent variable and the inverse of the estimated variance of the estimated vaccination coverage as the weights. For vaccination with the other vaccines, tests for linear trend were performed in SUDAAN using the RATIO procedure. Statistical significance was defined as p<0.05. Coverage estimates are not reported for small sample size (n<30) or relative standard error (standard error/estimates) >0.3.

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Results

The final sample adult component response rate for the 2015 NHIS was 55.2%. The final sample adult component response rates for estimating influenza vaccination coverage for the 2014–15 influenza season were 58.9% for 2014 and 55.2% for 2015. The total adult sample for influenza coverage estimation was 31,897 persons aged ≥19 years. Detailed information for vaccination coverage estimates stratified by selected variables is summarized (Box 2). These selected variables include health insurance status, having a usual place for health care, number of physician contacts, age group, nativity, number of years living in the United States, and citizenship.