Vaccination Coverage by Age 24 Months Among Children Born During 2018–2019 — National Immunization Survey–Child, United States, 2019–2021

Millions of young children are vaccinated safely in the United States each year against a variety of potentially dangerous infectious diseases (1). The Advisory Committee on Immunization Practices (ACIP) recommends routine vaccination against 14 diseases during the first 24 months of life* (2). This report describes vaccination coverage by age 24 months using data from the National Immunization Survey-Child (NIS-Child).† Compared with coverage among children born during 2016-2017, coverage among children born during 2018-2019 increased for a majority of recommended vaccines. Coverage was >90% for ≥3 doses of poliovirus vaccine (93.4%), ≥3 doses of hepatitis B vaccine (HepB) (92.7%), ≥1 dose of measles, mumps, and rubella vaccine (MMR) (91.6%), and ≥1 dose of varicella vaccine (VAR) (91.1%); coverage was lowest for ≥2 doses of hepatitis A vaccine (HepA) (47.3%). Vaccination coverage overall was similar or higher among children reaching age 24 months during March 2020 or later (during the COVID-19 pandemic) than among those reaching age 24 months before March 2020 (prepandemic); however, coverage with the combined 7-vaccine series§ among children living below the federal poverty level or in rural areas decreased by 4-5 percentage points during the pandemic (3). Among children born during 2018-2019, coverage disparities were observed by race and ethnicity, poverty status, health insurance status, and Metropolitan Statistical Area (MSA) residence. Coverage was typically higher among privately insured children than among children with other insurance or no insurance. Persistent disparities by health insurance status indicate the need to improve access to vaccines through the Vaccines for Children (VFC) program.¶ Providers should review children's histories and recommend needed vaccinations during every clinical encounter and address parental hesitancy to help reduce disparities and ensure that all children are protected from vaccine-preventable diseases.

Persistent disparities by health insurance status indicate the need to improve access to vaccines through the Vaccines for Children (VFC) program. ¶ Providers should review children's histories and recommend needed vaccinations during every clinical encounter and address parental hesitancy to help reduce disparities and ensure that all children are protected from vaccine-preventable diseases.
NIS-Child is a random-digit-dialed survey of households that includes children aged 19-35 months. Parents or guardians complete a telephone survey,** and consent to contact the child's vaccination providers is requested. With parental or guardian consent, identified providers are mailed a questionnaire to obtain vaccination information, which is synthesized to create the child's comprehensive vaccination history. Children born during 2018-2019 were identified from data collected during 2019-2021, resulting in 29,598 children with adequate provider data † † for analysis. The 2021 household response rate § § was 22.9%, and adequate provider data were obtained from 51.5% of households with completed interviews. Vaccination coverage by age 24 months was estimated using Kaplan-Meier techniques, except for the birth dose of ¶ Eligible children include those aged ≤18 years who are Medicaid-eligible, uninsured, American Indian or Alaska Native, or insured by health plans that do not fully cover routine immunization (if vaccination is received at a Federally Qualified Health Center or a rural health clinic). https://www.cdc. gov/vaccines/programs/vfc/ ** NIS-Child used a landline-only sampling frame during 1995-2010. During 2011-2017, the survey was conducted using a dual-frame design, with both mobile and landline sampling frames included. During 2018, NIS-Child returned to a single-frame design, with all interviews conducted by mobile telephone. † † Children with at least one vaccination reported by a provider and those who had received no vaccinations were considered to have adequate provider data. "No vaccinations" indicates that the vaccination status is known because the parent or guardian indicated there were no vaccinations and the providers returned no immunization history forms or returned them indicating that no vaccinations had been administered. §    are not yet available). § Includes children who might have received diphtheria and tetanus toxoids vaccine or diphtheria, tetanus toxoids, and pertussis vaccine. Healthy People 2030 target for ≥4 doses of DTaP is 90%. https://health.gov/healthypeople/objectives-and-data/browse-objectives/vaccination ¶ Statistically significantly different from 0 at p<0.05. ** Includes children who might have received measles, mumps, rubella, and varicella combination vaccine. Healthy People 2030 target for ≥1 dose of MMR is 90.8%.
https://health.gov/healthypeople/objectives-and-data/browse-objectives/vaccination † † Hib primary series: receipt of ≥2 or ≥3 doses, depending on product type received; full series: primary series and booster dose, which includes receipt of ≥3 or ≥4 doses, depending on product type received. § § One dose HepB administered from birth through age 3 days. ¶ ¶ Before 2020, first dose of HepA was recommended at age 12-23 months, with second dose administered 6-18 months after the first, depending upon the product type received. During 2020, recommendation was revised to 2 doses between ages 12 and 23 months, ≥6 months apart. Because children in this analysis were vaccinated under both recommendations, coverage estimates for both <24 months and <35 months are provided. *** Includes ≥2 doses of Rotarix monovalent rotavirus vaccine or ≥3 doses of RotaTeq RV5. If any dose in the series is either RV5 or unknown, the default is a 3-dose series. The maximum age for the final rotavirus dose is age 8 months, 0 days. † † † Doses must be ≥24 days apart (4 weeks with a 4-day grace period); doses could have been received during two influenza seasons. § (Figure).

Vaccination by Selected Sociodemographic Characteristics and Geographic Locations
Among children born during 2018-2019, coverage among those who were uninsured and those insured by Medicaid or other insurance ¶ ¶ ¶ was lower than that among privately insured children for all vaccines except the HepB birth dose, which was lower among uninsured children only ( Table 2). The proportion of children who were unvaccinated by age 24 months was eight times higher for uninsured compared with privately insured children. Compared with non-Hispanic White children, coverage with a majority of vaccines was lower among non-Hispanic Black or African American (Black) children, and coverage with ≥1 MMR dose, ≥1 VAR dose, rotavirus vaccine, ¶ ¶ ¶ "Other insurance" includes the Children's Health Insurance Program, military insurance, coverage via the Indian Health Service, and any other type of health insurance not mentioned elsewhere.

Summary
What is already known about this topic?
The Advisory Committee on Immunization Practices recommends routine vaccination against 14 diseases during the first 24 months of life.
What is added by this report?
Vaccination coverage among young children has remained high and stable for most vaccines, although disparities persist. The National Immunization Survey-Child identified no decline overall in routine vaccination coverage associated with the COVID-19 pandemic among children born during 2018-2019, although declines were observed among children living below the federal poverty level and in rural areas.
What are the implications for public health practice?
Additional efforts, such as providers reviewing children's immunization histories during every clinical encounter, recommending needed vaccinations, and addressing parental hesitancy, are warranted to reduce disparities so that all children can be protected from vaccine-preventable diseases.

Discussion
U.S. coverage with most recommended childhood vaccines has remained high and stable for many years. Increases in coverage by age 24 months were observed for most vaccines when This report did not identify any overall decline in vaccination coverage associated with the COVID-19 pandemic among all children. The youngest children were born in 2019. These children reached age 12 months in 2020 and 24 months in 2021; therefore, many of these children had vaccine doses recommended after the pandemic was declared in March 2020. In a more detailed analysis, coverage with the combined 7-vaccine series by age 24 months decreased 4-5 percentage points among children living below the federal poverty level or in rural areas (3). In addition, MMR coverage was 10 percentage points lower for children reaching age 13 months during April-May 2020 compared with those reaching age 13 months before and after this time frame, but coverage reached prepandemic levels by age 19 months (3). Similar decreases in coverage were observed in other data sources (4). The 2022 NIS-Child will include more children born shortly before or during the † † † † https://health.gov/healthypeople/objectives-and-data/browse-objectives/ vaccination pandemic, providing a more complete assessment of trends in vaccination coverage during the pandemic. Vaccination coverage declined for children living below the federal poverty level or in rural areas during the pandemic, and substantial variation in coverage by sociodemographic characteristics persists. As observed elsewhere (4), estimated coverage was highest among Asian children and lowest among Black children. Lower coverage was found among children living below the federal poverty level, without private health insurance, and in rural (non-MSA) areas.
If equity is to be achieved in the national childhood vaccination program, a number of obstacles must be overcome. Parents and other caregivers must have the willingness and the means to get children vaccinated. A recent report estimated that 6.5%-31.3% of nonvaccination among children could be attributed to parental hesitancy, depending upon the vaccine (5). CDC has developed a Vaccinate with Confidence strategy for identifying activities designed to bolster vaccine confidence and prevent outbreaks of vaccine-preventable diseases (6). Several additional evidence-based approaches to increasing vaccination coverage include strong health care provider recommendations, advocating for vaccines at every health care encounter, use of reminder and recall notices and standing orders, and the presence of state and local immunization information systems to provide consolidated immunization histories (7).
Logistical and financial barriers also must be addressed. The VFC program covers the cost of all recommended vaccines for eligible children; it is imperative that this program retain an adequate supply of participating vaccination providers and that families in need are aware of how to access it. Establishment of alternative vaccination settings such as pharmacies, emergency departments, hospitals, and outpatient subspecialty clinics might help address accessibility issues for underserved communities (8).
The findings in this report are subject to at least three limitations. First, the possibility of selection bias exists because of the low household interview response rate (ranging from 21%-26% during survey years 2017-2021) and the availability of adequate provider data for 49%-54% of those who completed interviews in survey years 2017-2021. Second, although the data were weighted to account for nonresponse and households without telephones, some bias could remain. Finally, coverage estimates could be incorrect if some vaccination providers did not return questionnaires or if administered vaccines were not documented accurately. Total survey error (9) for the 2021 survey year data was assessed and demonstrated that coverage was underestimated by 3.1 percentage points for ≥1 dose of MMR, 4.4 percentage points for the HepB birth dose, and 8.7 percentage points for the combined -vaccine series. An analysis of change in bias of vaccination coverage estimates from 2020 to 2021 determined that a meaningful change was unlikely. § § § § At the national level, coverage with most routine childhood vaccines is high; however, this high coverage is not distributed uniformly: coverage is lower among Black and Hispanic children, those of lower socioeconomic status, and those living in rural areas. Recent measles outbreaks ¶ ¶ ¶ ¶ and the diagnosis of a case of polio (10) serve as reminders that pockets of susceptibility can and do exist, even in a largely well-vaccinated society. Parents and providers must remain vigilant to ensure that all children are up to date with their routine vaccinations to protect them from vaccine-preventable diseases.