Vaccination Coverage among Adults in the United States, National Health Interview Survey, 2021

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Summary

Adults are at risk of illness, hospitalization, disability, and death from vaccine-preventable diseases (VPDs). The Centers for Disease Control and Prevention (CDC) recommends vaccinations for adults based on age, health conditions, prior vaccinations, and other considerations to prevent morbidity and mortality from VPDs. Updated CDC vaccination recommendations for adults  are published annually. Despite the burden and consequences of VPDs, vaccination coverage among U.S. adults remains low for most vaccines. In addition, large disparities in adult vaccination coverage by race and ethnicity and other demographic factors have remained mostly unchanged over the last several years.

To assess vaccination coverage among adults aged ≥19 years, CDC analyzed data from the National Health Interview Survey (NHIS). The NHIS is a continuous, cross-sectional national household survey of the noninstitutionalized U.S. civilian population. Interviews are conducted over the course of the year in a probability sample of households, and data are compiled and released on an annual basis. For this report, adult receipt of influenza, pneumococcal, herpes zoster, hepatitis A, and hepatitis B vaccines were assessed using the data collected in 2021. Trends in adult vaccination were examined during 2017–2021 to represent recent trends in adult vaccination.

Coverage for all vaccines differed by race and ethnicity with generally lower coverage among Black and Hispanic adults compared with White adults. Linear trend tests since 2017 indicated that coverage increased for influenza and herpes zoster vaccination, remained stable for pneumococcal vaccination among adults aged 19–64 years at increased risk of disease, and decreased for pneumococcal vaccination among adults aged ≥65 years.

Substantial improvement in adult vaccination uptake is needed to reduce the burden of VPDs nationally. Increasing the proportion of adults who receive recommended vaccines and ensuring equitable access to, and uptake of recommended vaccines is a high-priority public health issue.

Methods

The NHIS is a continuous, cross-sectional national household survey of the noninstitutionalized U.S. civilian population conducted by the U.S. Census Bureau for CDC’s National Center for Health Statistics. Due to data collection difficulties posed by the COVID-19 pandemic, NHIS interviews were conducted by telephone starting in March 2020, and continued to be attempted first by telephone from January to April 2021, with in-person visits used only to follow up for non-response. Starting in May 2021, interviewers were instructed to return to regular in-person survey interviewing procedures. Interviewers were given flexibility to continue using telephone first contact attempts based on local COVID-19 conditions (1). The objectives of NHIS are to monitor the health of the U.S. population and provide estimates of health indicators, health care use and access, and health-related behaviors (2). Non-institutionalized adults aged ≥19 years with interviews conducted during August 2020–June 2021 (for influenza vaccination) and January 2021–December 2021 (for pneumococcal, herpes zoster, hepatitis A, and hepatitis B vaccination) were included in this analysis. The total sample of persons aged ≥19 years was 29,142 in 2021. The final sample adult core response rate was 50.9% for the 2021 NHIS. Questions about receipt of vaccinations recommended for adults are asked of one randomly selected adult within each family in the household. Vaccination questions included in the 2021 NHIS were: for influenza vaccination, respondents were asked if they had received an influenza shot or nasal spray during the preceding 12 months and, if so, in which month and year; for pneumococcal vaccination, respondents were asked if they had ever had a pneumonia shot, and if yes, how many doses were received; for hepatitis A vaccination, respondents were asked if they had ever received the hepatitis A vaccine; for hepatitis B vaccination, respondents were asked if they had ever received the hepatitis B vaccine; and for herpes zoster vaccination, respondents were asked if they had ever received a shingles vaccine and, if yes, what type of vaccine received (zoster vaccine live or recombinant zoster vaccine), number of vaccine doses received, and timing of vaccine receipt.

Weighted data were used to produce national vaccination coverage estimates. For non-influenza adult vaccination coverage estimates, the weighted proportion of respondents who reported receiving selected vaccinations was calculated. To better assess season-specific influenza vaccination coverage, the Kaplan-Meier survival analysis procedure was used (3). Race and ethnicity were categorized into five mutually exclusive groups as follows: White, Black, Hispanic, Asian, and Other. In this report, persons characterized as being of White, Black, Asian, or Other race identified as non-Hispanic. Persons characterized as Hispanic might be of any race. Persons characterized as Other include persons who identified as American Indian, Alaska Native, Native Hawaiian, Pacific Islander, or any other race and persons who identified multiple races. We did not report tetanus and diphtheria (Td)/tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccination since this information was not collected in the 2020 and 2021 NHIS.

Point estimates and 95% confidence intervals (CIs) were calculated using SUDAAN software (Research Triangle Institute, Research Triangle Park, NC, version 11.0.1) to account for the complex sample design. Differences were measured as the simple difference between 2020 and 2021 for pneumococcal and herpes zoster vaccination coverage, and between 2018 and 2021 for hepatitis A and hepatitis B vaccination coverage due to the NHIS survey question rotation. T-tests were used for comparisons between data years and for comparisons of each level of each respondent characteristic to a chosen referent level (e.g., for race and ethnicity, White was the reference group). Statistical significance was defined as p<0.05. Coverage estimates are not reported for small sample size (n<30) or large relative standard errors (standard error/estimate >0.3). Trends in adult vaccination were assessed from 2017 through 2021, including influenza, pneumococcal, and herpes zoster vaccinations.

Results

Pneumococcal Vaccination

  • Pneumococcal vaccination coverage overall (≥1 dose of any type of pneumococcal vaccine) among adults aged 19–64 years at increased risk for pneumococcal disease was 22.2% in 2021, similar to the estimate for 2020.
    • Coverage among White adults aged 19–64 years at increased risk was higher (23.3%) compared with Hispanic (19.0%) and Asian (16.9%) adults.
  • Coverage with ≥1 dose of any type of pneumococcal vaccine among adults aged ≥65 years was 65.8%, similar to the estimate for 2020.
    • Coverage among White adults aged ≥65 years (70.1%) was higher compared with Black (54.8%), Hispanic (46.2%), and Asian (55.8%) adults.

TABLE 1. Estimated proportion of adults aged ≥19 years who ever received pneumococcal vaccination by increased-risk status and race and ethnicity — National Health Interview Survey, United States, 2021

Herpes Zoster Vaccination

  • Overall, herpes zoster vaccination coverage (≥1 dose of any type of herpes zoster vaccination) in 2021 was 32.6% among adults ≥50 and 41.1% among adults aged ≥60 years, higher than estimates for 2020.
    • White adults aged ≥50 and ≥60 years had higher coverage compared with Black, Hispanic, and Other adults.
  • Zoster vaccine live (ZVL) coverage (≥1 dose, no longer available for use in the U.S. since November 2020) in 2021 was 16.6% among adults aged ≥50 years, 23.3% among adults aged ≥60 years, and 28.3% among adults aged ≥65 years, all lower than estimates for 2020.
  • Recombinant zoster vaccine (RZV) coverage (≥1 dose, Advisory Committee on Immunization Practices [ACIP] recommended for immunocompetent adults aged ≥50 years since 2017) was 18.6% among adults aged ≥50 years, including 12.2% among adults aged 50–59 years, 20.1% among adults aged 60–64 years, and 22.8% among adults aged ≥65 years, all higher than estimates for 2020.
    • Coverage was 22.0% among adults aged ≥60 years, higher than the estimate for 2020.
  • RZV coverage (at least 2 doses) was 15.4% among adults aged ≥50 years, including 9.5% among adults aged 50–59 years, 16.8% among adults aged 60–64 years, and 19.2% among adults aged ≥65 years, all higher than estimates for 2020.
    • Coverage was 18.5% among adults aged ≥60 years, higher than the estimate for 2020.

TABLE 2. Estimated proportion of adults aged ≥50 years who ever received herpes zoster vaccination, by age and race and ethnicity — National Health Interview Survey, United States, 2021

Hepatitis A vaccination (at least one dose, ever)

  • Among adults aged ≥19 years, hepatitis A vaccination coverage was higher in 2021 than in 2018 overall (24.8%) and among travelers (33.8%).
  • Coverage was higher among travelers (33.8%) than nontravelers (19.3%).
  • Among all adults ≥19 years, coverage among White adults (24.8%) was higher than Black (19.4%) but lower than Asian (33.1%) adults.
    • Among adults aged 19–49 years, White adults had higher coverage (37.5%) than Black (25.5%) and Hispanic (29.5%) adults.

Table 3. Estimated proportion of adults aged ≥19 years who received hepatitis A vaccination, by age group, increased-risk status, and race and ethnicity — National Health Interview Survey, United States, 2021

Hepatitis B vaccination (at least one dose, ever)

  • Hepatitis B vaccination coverage in 2021 was 34.2% among adults aged ≥19 years overall and 43.1% among travelers, lower than estimates for 2018.
  • Among all adults ≥19 years, coverage among White adults (34.5%) was higher than Black (28.3%) but lower than Asian (45.6%) and Other (40.2%) adults.
    • Among adults aged 19–49 years, White adults had higher coverage (48.4%) compared with Black (34.3%) and Hispanic (37.5%) but lower than Asian (53.5%) adults.
    • Among adults aged 30–59 years, White adults had higher coverage (38.4%) compared with Black (31.2%) and Hispanic (31.5%) but lower than Asian (47.0%) adults.
  • Hepatitis B vaccination coverage was higher among travelers (43.1%) than nontravelers aged ≥19 years (28.7%) and higher among adults with diabetes aged 19–59 years (35.9%) than adults with diabetes aged ≥60 years (19.7%).

Table 4. Estimated proportion of adults aged ≥19 years who received hepatitis B vaccination, by age group, increased-risk status, and race and ethnicity — National Health Interview Survey, United States, 2021

Trends in Adult Vaccination Coverage

  • Trends in coverage from 2017–2021 with selected vaccines recommended for adults are shown in the Figure.
  • Increases in coverage were observed for influenza vaccination among adults aged ≥19 years (annual average percentage point increase: 1.4%, 95% CI: 0.7, 2.0) and influenza vaccination among adults aged ≥19 years at high risk (annual average percentage point increase: 1.5%, 95% CI: 1.0, 2.0).
  • Increases in coverage were observed for herpes zoster vaccination among adults aged ≥60 years (annual average percentage point increase: 1.7%, 95% CI: 1.3, 2.1).
  • Decreases in coverage were observed for pneumococcal vaccination among adults aged ≥65 years (annual average percentage point decrease: -0.8%, 95% CI: -1.3, -0.3), but coverage for pneumococcal vaccination among adults aged 19–64 years at increased risk remained stable from 2017–2021.

Figure. Estimated proportion of adults aged ≥19 years who received selected vaccines, by age group and risk status — National Health Interview Survey, United States, 2017–2021

Discussion

NHIS data from 2021 indicate that many adults in the United States remained unprotected against VPDs. Small increases in adult vaccination coverage compared with prior years were observed for herpes zoster and hepatitis A vaccinations, and small decreases were observed for hepatitis B vaccination. Linear trend tests since 2017 indicated that coverage increased for influenza (aged ≥19 and aged ≥19 years at high risk) and herpes zoster (aged ≥60 years) vaccination but decreased for pneumococcal vaccination among adults aged ≥65 years. While reductions in vaccine uptake due to the COVID-19 pandemic have been described (4, 5), this report assessed cumulative vaccination coverage over time, and any disruptions in health care access or utilization since 2020 would not be expected to show a substantial impact on the estimates presented here. A separate analysis of adults in NHIS who reached age 65–70 years and became eligible for pneumococcal vaccination after the start of the COVID-19 pandemic in 2020 did not show a pandemic effect on pneumococcal vaccination coverage, but data from the Behavioral Risk Factor Surveillance System suggest a modest decrease in pneumococcal vaccination among older adults that might be associated with the COVID-19 pandemic (6). Racial and ethnic differences in vaccination coverage persisted for all vaccinations, with generally lower coverage among Black and Hispanic adults compared with White adults.

Many changes to the ACIP recommendations have occurred since 2017 for the vaccines assessed in this report. While pneumococcal recommendations have changed since ACIP recommended 23-valent pneumococcal polysaccharide vaccine (PPSV23) vaccination of all adults aged ≥65 years and younger adults with certain medical conditions in 1997 (7), at least one dose of pneumococcal vaccine has been recommended for eligible adults throughout the period assessed in this report. Currently, ACIP recommends 15-valent or 20-valent pneumococcal conjugate vaccine (PCV) for PCV-naïve adults previously eligible for pneumococcal vaccine; when PCV15 is used, it should be followed by a dose of PPSV23 ≥1 year later (8). In 2008, ACIP recommended ZVL for adults aged ≥60 years and in 2017, ACIP preferentially recommended RZV for use in immunocompetent adults aged ≥50 years over ZVL due to higher and longer-lasting efficacy and recommended RZV vaccination of persons who previously received ZVL (9, 10).  ZVL has not been available for use in the U.S. since November 2020. In 2021, ACIP recommended two doses of RZV for use in adults aged ≥19 years who are or will be immunodeficient or immunosuppressed because of disease or therapy (11). The 2022 NHIS data will be the first full year of data for assessing coverage among those aged ≥19 years, which will be monitored in future reports. ACIP has recommended a hepatitis B vaccine series since 1991 for travelers to or persons working in countries with high or intermediate hepatitis B endemicity (12) and since 2011 for unvaccinated adults with diabetes aged 19–59 years (13). ACIP recommended Heplisav-B (HepB-CpG), a yeast-derived vaccine prepared with a novel adjuvant, administered as a 2-dose series for use in persons aged ≥18 years in 2018 (14). In 2022, ACIP recommended universal hepatitis B vaccination for all adults aged 19–59 years (15), which will be monitored in future reports, and for adults 60 years and older at increased risk or who desire protection from hepatitis B.

Since the 2010–11 influenza season, ACIP has recommended annual influenza vaccination for all persons aged ≥6 months (16). Though influenza vaccination coverage has continued to increase among all adults since this universal recommendation, coverage remains low with only approximately half of adults vaccinated in the 2020–21 season.

Questions about receipt of COVID-19 vaccine were added to the NHIS beginning in April 2021. Coverage with at least one dose of COVID-19 vaccine among adults assessed in the NHIS from April–December 2021 was 72.0%, compared with 67.4%–75.2% in the National Immunization Survey-Adult COVID Module during July–September 2021 (17). While COVID-19 vaccination recommendations have changed since 2021, data from future NHIS survey years can be used to assess associations of COVID-19 vaccination with other adult vaccines and demographic and access to care variables not collected in other surveys. The most current estimates of COVID-19 vaccination coverage in the United States can be found on CDC’s COVID Data Tracker and COVIDVaxView websites (17, 18).

Limitations

The estimates in this report are subject to several limitations. First, all data rely on respondent self-report and were not validated with medical records. However, adult self-reported vaccination status has been shown to be ≥70% sensitive in one or more studies for influenza, pneumococcal, herpes zoster, and hepatitis B vaccines and ≥70% specific in one or more studies for all except hepatitis B vaccination (19–21). Adults who were recommended to be vaccinated for hepatitis B as children might not be able to recall vaccination. Data from the National Immunization Survey-Teen show that hepatitis B vaccination coverage was 77% among adolescents aged 17 years in 2006, who would be age 32 years in 2021, and 89% for adolescents aged 13 years in 2006, who would be age 28 years in 2021 (22). Second, the NHIS response rate was 50.9% in 2021. Nonresponse bias can result if respondents and non-respondents differ in their vaccination behaviors and if survey weighting does not fully correct for this. Third, NHIS data from 2020 at the start of the COVID-19 pandemic and from January through April 2021 were obtained by telephone rather than in-person interviews and the impact of that change on validity of these estimates is unknown. Finally, the NHIS sample excludes persons in the military and those residing in institutions, which might result in underestimation or overestimation of adult vaccination coverage levels.

Conclusion

Coverage increased for influenza and herpes zoster vaccination in recent years. Disparities in vaccination coverage by race and ethnicity were seen for all vaccines assessed. Increasing the proportion of adults who receive recommended vaccines and ensuring equitable access to, and uptake of recommended vaccines is a high-priority public health issue.

 

Authors: Mei-Chuan Hung, MPH, PhD1,2; Anup Srivastav, B.V.Sc.&A.H., PhD1,2; Peng-Jun Lu, MD, PhD1; Carla L. Black, PhD1; Tara C. Jatlaoui, MD, MPH1; Megan C. Lindley, MPH1; James A. Singleton, PhD1

1Immunization Services Division, National Center for Immunization and Respiratory Diseases, CDC
2Leidos, Inc, Atlanta, GA

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