Discussion

In 2015, adult vaccination coverage in the United States remained similar to 2014, except for modest increases in influenza (adults aged ≥19 years; for influenza coverage, increase compared with the 2013–14 season), pneumococcal (adults aged 19–64 years with increased risk), Tdap (adults aged ≥19 years), herpes zoster (adults aged ≥60 years) and hepatitis B (HCP aged ≥19 years). Overall, although the point estimates for each year varied by only a few percentage points, linear trend tests indicated that during 2010–2015, vaccination coverage increased for influenza and pneumococcal vaccines (all age and risk groups), Tdap (adults aged 19–64 years), hepatitis A (adults aged ≥19 years), herpes zoster (adults aged ≥60 years), and HPV (females aged 19–26 years) vaccines and during 2012–2015 and 2011–2015, for Tdap vaccine (adults aged ≥65 years) and HPV vaccine (males aged 19–26 years), respectively. Although these increases were small, collectively they might have resulted in meaningful reductions in disease among adults (11,12). During 2010–2015 there was a decreasing trend observed for hepatitis B vaccination among persons aged ≥19 years overall (Figure). Vaccination coverage estimates for three of the four vaccines in this report that are included in Healthy People 2020 (influenza, pneumococcal, and hepatitis B [for HCP] vaccines) were below the respective target levels, including among insured adults and adults with multiple health care visits in the past year. Herpes zoster vaccination coverage in 2015 was 0.6 percentage points above the Healthy People 2020 target of 30%. Racial/ethnic differences in vaccination coverage persisted for all seven vaccines discussed in this report. These data indicate multiple missed opportunities for vaccination and the need to increase routine assessment of adult vaccination needs, and vaccination with needed vaccines.

The figure above shows the estimated proportion of adults aged equal to or greater than 19 years who received selected recommended vaccines, by age group and increased risk status, on the basis of data from the National Health Interview Survey for 2010–2015.

Influenza Vaccination

Overall, less than 45% of adults aged ≥19 years were vaccinated annually during the influenza seasons spanning the 2009–10 through 2014–15 seasons, well below the Healthy People 2020 target of 70% for annual vaccination of adults against seasonal influenza. Vaccination coverage among HCP with and without direct patient care also remained far below the Healthy People 2020 target for HCP of 90%. Previous studies of influenza illnesses and hospitalizations that could be averted by vaccination have indicated that higher vaccination rates could have resulted in prevention of a substantial number of influenza cases and hospitalizations (11,12). More effort is needed to reach the Healthy People 2020 targets to benefit more fully from influenza vaccines. Ensuring that all persons who visit a health care provider during the influenza season receive a vaccination recommendation and offer from their provider and use of vaccination information systems could increase influenza vaccination rates (13,14). Implementing interventions shown effective in increasing uptake of influenza vaccination among HCP including access to vaccination at the workplace at no cost for >1 day could improve coverage in this population (15–17).

Pneumococcal Vaccination

The proportion of pneumococcal vaccination by type of vaccine (PCV13 or PPSV23) was not measured in the 2015 NHIS. The overall pneumococcal vaccination estimates in this report include respondents who received PCV13 and/or PPSV23. Ascertaining type-specific pneumococcal vaccination via self-report through survey questions presents challenges, particularly because current information indicates that physicians do not routinely advise their patients about the types of vaccines they use (5) and the complexity of the pneumococcal vaccination recommendations (different for adults with no previous pneumococcal vaccination, those who might have received PCV13 previously, and PCV13-naïve adults previously vaccinated with PPSV23) (18–20). Pneumococcal vaccination of persons aged 19–64 years at increased risk and vaccination of persons aged ≥65 years increased during the 6 years covered in this report; however, both remain well below Healthy People 2020 targets of 60% for persons aged 18–64 years at increased risk and 90% for adults aged ≥65 years. Among persons aged ≥65 years, using PCV13 in series with PPSV23 could prevent an estimated 230 cases of invasive pneumococcal disease and approximately 12,000 cases of community-acquired pneumonia over the lifetime of a single cohort of persons currently aged 65 years through life expectancy (18). Achieving higher pneumococcal vaccination levels could improve these benefits.

Tetanus Toxoid-Containing Vaccination

A single dose of Tdap is recommended for all adults aged ≥19 years who have not yet received a dose, including those aged ≥65 years, and should be administered regardless of interval since the most recent Td (21). Although there were modest increases in Tdap vaccination of adults from 2010 to 2015, coverage has remained low for all age groups and among adults living with an infant aged <1 year. Recent studies have shown that Tdap vaccination is highly effective at preventing pertussis among adolescents in the short-term; however, there is rapid waning of immunity in the years following Tdap receipt (22–28). Evidence indicates that the duration of protection wanes more quickly from acellular pertussis-containing vaccines than immunity derived from whole-cell pertussis vaccine formulations, and that the type of priming dose received (i.e., acellular pertussis vaccine or whole-cell pertussis vaccine) influences the durability of immunity (22–24,29,30). There is evidence that receiving at least a single dose of whole-cell pertussis vaccine, especially as the first dose of a pertussis-containing vaccine series, provides greater and longer-lived protection, irrespective of the type of subsequent doses (22–24,29,30). In the United States, booster doses with acellular pertussis-containing vaccines for infants and children (the fourth and fifth doses of the childhood series administered at ages 15–18 months and 4–6 years, respectively) were first recommended to replace whole-cell pertussis vaccine formulations in 1992 and primary doses administered at ages 2, 4, and 6 months were recommended in 1997 (22–24). Given the timing of the transition, many young and older adults would have been primed with whole-cell pertussis vaccine and might have more durable immunity (22,24,26). Despite the observed limitations of Tdap, current vaccination strategies remain the best approach to reducing the burden of pertussis among adolescents and adults (24). Health care providers should not miss an opportunity to vaccinate adults aged ≥19 years who have not received Tdap previously. Pregnant women are recommended to receive a dose of Tdap during every pregnancy, optimally between 27 and 36 weeks gestation, to provide protection to young infants through maternal antibody transfer (31).

Hepatitis A Vaccination

Hepatitis A vaccination is recommended for persons traveling to or working in countries that have high or intermediate endemicity of hepatitis A, if some risk factor is present (e.g., on the basis of lifestyle, occupation, or medical condition) or for any person seeking protection from hepatitis A virus infection (6). Information was available only for those with foreign travel to areas of high or intermediate endemicity and those with chronic liver disease. Although hepatitis A vaccination of adults who had traveled outside the United States to a country in which hepatitis A is of high or intermediate endemicity was higher in 2015 and preceding years than among adults who did not travel outside the United States or had traveled only to countries in which the disease is of low endemicity, overall hepatitis A vaccination among travelers and persons with chronic liver disease has remained low. Health care providers are encouraged to assess the needs of their patients for hepatitis A vaccine and offer it whenever appropriate.

Hepatitis B Vaccination

Hepatitis B vaccination coverage in 2015 among persons with diabetes showed no improvement over estimates obtained before this recommendation, which underscores the need to improve awareness of increased risk for contracting acute hepatitis B among persons with diabetes and to increase hepatitis B vaccination in this population. Similar to hepatitis A vaccination, overall hepatitis B vaccination among travelers and persons with chronic liver disease has remained low, although hepatitis B vaccination of persons who had traveled outside the United States to a country in which hepatitis B is of high or intermediate endemicity was higher in 2015 and preceding years than among respondents who did not travel outside the United States or had traveled only to countries in which the disease is of low endemicity. During 2010–2015, estimates of hepatitis B vaccination among HCP have not improved, ranging from 61%–65%, well below the Healthy People 2020 target of 90%.

Herpes Zoster Vaccination

Herpes zoster vaccination coverage for adults aged ≥60 years was 30.6% in 2015, a 2.7 percentage point increase compared with 2014, and 0.6 percentage points above the Healthy People 2020 target of 30%. Although the Healthy People 2020 target was achieved, approximately 70% of adults recommended to receive this vaccine remain unprotected. Although shortages of herpes zoster vaccine that likely contributed to low uptake during the first years after licensure were resolved, other barriers persist, particularly the high cost for providers to purchase a supply, challenges to stocking the vaccine (which requires freezer storage), coverage for the vaccine under Medicare Part D, which results in billing challenges for medical providers other than pharmacist vaccine providers, and out-of-pocket payments for some Medicare Part D beneficiaries depending on their specific plan (32,33). Although health care provider recommendations for vaccination are strongly associated with a patient’s receipt of vaccines (9,13,14), individual awareness of vaccine-preventable disease consequences can also influence vaccination behavior. For example, rates of herpes zoster vaccination were increased among persons who witnessed friends or family members experience herpes zoster (34), particularly if the herpes zoster was severe (CDC, Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, unpublished data, 2016). In one study (34), blacks had a lower rate of self-reported prevalence of herpes zoster and of witnessing friends or family members with herpes zoster compared with whites. These factors might have influenced perceived risk for herpes zoster among blacks in that study, their interest in herpes zoster vaccination, and contributed to the lower vaccination levels among blacks observed in this study population (34). Vaccination with the current live-attenuated herpes zoster vaccine is contraindicated in immunocompromised persons (35). Studies and clinical trials of other herpes zoster vaccines have been conducted to identify immunizing agents that could protect more population groups, including selected populations of immunocompromised patients considered at increased risk for herpes zoster infection and complications (36–42) and older adults (40–42).

HPV Vaccination

ACIP has recommended routine vaccination at age 11 or 12 years for girls since 2006 and for boys since 2011. ACIP also recommends vaccination for females aged 13–26 years and for males aged 13–21 years who have not been vaccinated previously or who have not completed the 3-dose series; males aged 22–26 years may be vaccinated (43,44). Although vaccination coverage has increased since a licensed HPV vaccine has been available and recommended by ACIP, many adolescent and young adult females and males remain unvaccinated and vulnerable to develop cancers that safe, effective HPV vaccines can prevent (5,43,45).

In 2015 among women and men aged 19–26 years, 6.2% and 6.9% reported receiving the first dose of HPV vaccine at age 11–12 years, respectively, with most (91.8% of females and 88.8% of males) reporting receipt at age ≥13 years, consistent with the fact that female respondents aged ≥22 years and all male respondents would have been aged >13 years at the time HPV vaccination was first recommended. In 2015, approximately 12% of females and 3% of males aged 19–26 years not vaccinated at age ≤18 years reported receiving the first dose of HPV vaccine as catch-up at age 19–26 years. Since HPV vaccine licensure, multiple cohorts of unvaccinated adolescents and young adults have accumulated. Based on 2015 data alone, as many as 9.1 million women and approximately 13.9 million men aged 19–26 years were unvaccinated and might benefit from HPV vaccination assuming no contraindications to vaccination. Until HPV vaccination increases among adolescents, a high proportion of unprotected young women and men eligible for HPV vaccination will be expected. For example, in the 2015 National Immunization Survey – Teen (45), provider-reported vaccination histories indicated that among females and males aged 17 years, 29.4% (582,947) and 49.6% (980,637), respectively, were unvaccinated (having not received at least one HPV vaccine dose) (45). These estimates reflect the current pool of females and males who could benefit from catch-up vaccination and the number of unprotected older adolescents adding to that pool annually. Studies have found that although HPV infection increases with increasing age after sexual debut, most women have not been infected with all the high risk HPV types targeted by the vaccines (46,47), supporting implementation of ACIP-recommended catch-up vaccination, because vaccination can protect against HPV types for which vaccination candidates have not been infected. Results from modeling and studies of the cost-effectiveness of HPV vaccination of young women and men suggest that catch-up vaccination could reduce the amount of time needed to achieve population level impacts of vaccination on infections with HPV vaccine types and sequelae such as cancer (48–55). Findings from initial studies of vaccine impact in settings in which catch-up vaccination programs were successful in achieving high coverage rates among young women are consistent with these models (56–59). Although cost-effectiveness studies indicate that catch-up vaccination might become less favorable over time, a long-term strategy of HPV vaccination of young adult females through age 18–26 years could be considered cost-effective and, when combined with an adolescent vaccination program, appears to represent an effective strategy (49,50,54,55,60–67). Data for the years 2008–2012 from population-based cancer registries (that participate in CDC’s National Program of Cancer Registries and the National Cancer Institute’s Surveillance, Epidemiology, and End Results program) indicated that of the average of 38,793 HPV-associated cancers diagnosed annually (11.7 per 100,000 persons; including 23,000 [13.5] among females and 15,793 [9.7] among males), 30,700 (79%) were estimated to be attributable to HPV based on polymerase chain reaction genotyping studies (68). Among these HPV-associated cancers, 24,600 (80%) were attributable to HPV types 16 and 18, which can be prevented by HPV vaccines (bivalent, quadrivalent and 9-valent vaccines), and 3,800 (12%) were attributable to the five additional HPV types which can be prevented by the 9-valent vaccine (HPV types 31, 33, 45, 52, 58). Although these findings represented an overall increase in HPV-associated cancer incidence from 10.8 per 100,000 persons to 11.7 per 100,000 persons, compared with a previous analysis which reported cases diagnosed annually during 2004–2008 (69), impact of vaccination activities on HPV-attributable cancers will not be observed for decades after vaccine introduction. However, impact of HPV vaccination programs already has been observed on HPV prevalence, genital warts and cervical precancers (70–78). Increasing HPV vaccination coverage could lead to greater decreases in HPV attributable diseases in the United States. Continued efforts are needed to improve coverage among members of the primary target group for HPV vaccine, girls and boys aged 11–12 years (79), and among all racial and ethnic groups. To reduce the amount of time needed to achieve population level impacts of vaccination such as reduction in HPV-associated cancer incidence, efforts also are needed to improve catch-up vaccination among those who have not started or completed their vaccination.

Racial and Ethnic Differences in Vaccination

Compared with 2014, racial/ethnic differences in vaccination coverage persisted for all seven vaccines in this report. Generally higher coverage was observed for whites compared with most other groups. These differences widened for pneumococcal and herpes zoster vaccination (due primarily to increases among whites). Blacks, Hispanics, and Asians had lower vaccination coverage than that of whites for all of the vaccines routinely recommended for adults, with just a few exceptions. Among HCP, there were differences for influenza, Tdap, and hepatitis B vaccination, with white HCP generally having higher vaccination coverage compared with black and Hispanic HCP.

The findings provided in this report are consistent with those from a study on racial and ethnic disparities in vaccination coverage among adults using 2012 NHIS data (80). Five vaccines were included in this study (influenza, pneumococcal [both PPSV23 and PCV13], tetanus (Td), herpes zoster, and HPV). There were vaccination disparities for most other groups compared with whites for 17 of the 24 comparisons by vaccine and age/target groups, even after adjusting for demographic and access-to-care characteristics. In most of the logistic models, whites reported receipt of vaccinations more often than blacks, Hispanics, and Asians after controlling for other demographic and access-to-care characteristics. Factors that were independently associated with receipt of most of the examined vaccines included race and ethnicity, age, sex, education, health insurance, and having a usual place for health care. The number of physician visits in the past 12 months was independently associated with receipt of all the vaccinations assessed in this study. Results from this study indicated that racial and ethnic differences in vaccination levels narrow when adjusting for socioeconomic factors analyzed in this survey, but are not eliminated, suggesting that other factors that are associated with vaccination disparities are not measured by the NHIS and could also contribute to the differences in coverage.

Previous research has indicated a variety of factors that contribute to racial/ethnic differences in adult vaccination rates, including patient, provider, and system factors (81–84). Standardized offering of vaccines reduces these differences (85,86). Using a combination of patient tracking, vaccination reminders for providers and patients, and patient outreach and assistance also reduces racial/ethnic vaccination differences (87). Incorporating standards for adult vaccination practices, which include routinely assessing vaccination needs during clinical encounters, providing a strong recommendation for vaccination to patients with indications, and then offering vaccination at the visit (14), can reduce vaccination disparities.

Improving Adult Vaccination Coverage

Adult vaccination coverage remains low for most routinely recommended vaccines. Racial/ethnic differences in coverage persisted for all seven vaccines in this report with higher coverage, generally, for whites compared with most other groups. Factors that contribute to low adult vaccination rates (including patient- and provider-level barriers and systems-related factors) have been described (5,88–96) and effective, evidence-based strategies to improve vaccine use have been reported (13,88). The National Vaccine Advisory Committee published updated standards for adult immunization practice in 2014 with the intent of improving adult vaccination coverage of ACIP-recommended vaccines. This guidance calls on health care providers, including those who do not stock vaccines, to 1) assess the vaccination status of patients at every clinical encounter; 2) recommend needed vaccines for patients; 3) offer recommended vaccines or, for providers who do not stock a needed vaccine, refer patients to a vaccine provider; and 4) document vaccines administered, including in immunization information systems when available for use among adult patients (14). Nationwide adoption of electronic health records (EHRs), electronic patient portals, and patient-directed clinical decision support delivered via patient portals offer opportunities for innovative approaches to improving adult vaccination rates. For example, to improve influenza vaccination among eligible adult patients, a protocol is being evaluated in a large multispecialty group practice. The protocol uses patient-directed clinical decision support involving EHR patient portal messages and interactive voice recognition calls to promote influenza vaccination and obtain patient self-report of vaccines received outside the practice as well as information on barriers to vaccination (97). To improve administration and documentation of receipt of Tdap, consensus-based teams of clinicians, nurses, medical assistants, and other support staff have used an automated clinical reminder system to provide patient-specific vaccination recommendations to clinicians at the point of care (98). Seven large medical groups participating in an adult immunization best practices collaborative in six states have used a clinical data repository comprised of claims data, billing data, and data from electronic clinical systems to increase influenza vaccination in adults aged ≥18 years and pneumococcal vaccination successfully among groups at increased risk for invasive pneumococcal disease (99,100). Various strategies have been evaluated for increasing influenza, Tdap, and HPV vaccination in select populations such as pregnant women and women in the general population, including interventions to overcome provider and system barriers (e.g., physician education and reminders) (101), interventions to increase demand for vaccination (e.g., text messaging encouraging vaccination in an ambulatory obstetric population) (102), and interventions to enhance vaccine access (103–107). The expanded availability of vaccine services in pharmacies and other retail settings has also improved vaccine accessibility (108–110). To increase targeted vaccination coverage, the Task Force on Community Preventive Services recommends a combination of strategies that include selected interventions from two or three categories: increasing community demand for vaccinations, enhancing access to vaccination services, and provider- or system-based interventions (13,111).