The Advisory Committee on Immunization Practices (ACIP) recommends that children be
vaccinated against 14 potentially serious illnesses during the first 24 months of
life (
1
). CDC used data from the National Immunization Survey-Child (NIS-Child) to assess
vaccination coverage with the recommended number of doses of each vaccine at the national,
state, territorial, and selected local levels* among children born in 2015 and 2016.
Coverage by age 24 months was at least 90% nationally for ≥3 doses of poliovirus vaccine,
≥1 dose of measles, mumps, and rubella vaccine (MMR), ≥3 doses of hepatitis B vaccine
(HepB), and ≥1 dose of varicella vaccine, although MMR coverage was <90% in 20 states.
Children were least likely to be up to date by age 24 months with ≥2 doses of influenza
vaccine (56.6%). Only 1.3% of children born in 2015 and 2016 had received no vaccinations
by the second birthday. Coverage was lower for uninsured children and for children
insured by Medicaid than for those with private health insurance. Vaccination coverage
can be increased by improving access to vaccine providers and eliminating missed opportunities
to vaccinate children during health care visits. Increased use of local vaccination
coverage data is needed to identify communities at higher risk for outbreaks of measles
and other vaccine-preventable diseases.
The NIS-Child is a random-digit–dialed telephone survey
†
of parents or guardians of children aged 19–35 months. Respondents are asked to provide
contact information for all providers who administered vaccines to their children.
With parental consent, a survey is mailed to each identified provider, requesting
the child’s vaccination history. Multiple responses for an individual child are synthesized
into a comprehensive vaccination history which is used to estimate vaccination coverage.
To estimate coverage for the 25,059 children with adequate provider data
§
born in 2015 and 2016, NIS-Child data from 2016–2018 were combined; for survey year
2018, the Council of American Survey Research Organizations’ response rate was 24.6%,
and 54.0% of children with household interviews had adequate provider data.
¶
With this report, CDC has transitioned to reporting NIS-Child data by birth year rather
than survey year. Vaccination coverage by age 24 months was estimated using Kaplan-Meier
(time to event) analysis to account for children who were aged <24 months on the date
vaccination status was assessed. Coverage with ≥2 doses of hepatitis A vaccine (HepA)
was assessed at 35 months (the maximum age included in the survey), because the second
dose of HepA can be administered as late as age 41 months under the current schedule.
Previous NIS-Child weighting methods were modified to optimize estimation by birth
year and to reflect the shift from a dual landline and cellular telephone sample frame
to an exclusively cellular telephone sampling frame in 2018.** Differences in coverage
estimates were evaluated using t-tests on weighted data; p-values of <0.05 were considered
statistically significant. Analyses were performed using SAS (version 9.4; SAS institute)
and SUDAAN (version 11.0.1; Research Triangle Institute). No evidence for a change
in survey accuracy from the 2017 to 2018 survey year was detected (https://www.cdc.gov/vaccines/imz-managers/coverage/childvaxview/pubs-presentations/NIS-child-vac-coverage-estimates-2014-2018-tables.html#supp-table-01)
(
2
).
National Vaccination Coverage
Coverage by age 24 months was ≥90% for ≥3 doses of poliovirus vaccine (92.7%), ≥1
dose of MMR (90.4%), ≥3 doses of HepB (91.0%), and ≥1 dose of varicella vaccine (90.0%)
(Table 1). Compared with estimates for children born in 2013 and 2014, coverage for
children born during 2015–2016 increased for the HepB birth dose (3.2 percentage points),
≥1 dose of HepA (1.5 percentage points), and ≥2 doses of influenza vaccine (3.6 percentage
points). Coverage with ≥2 HepA doses by age 35 months increased from 74.0% for children
born during 2013–2014 to 76.6% for children born during 2015–2016. Children were least
likely to be up to date by age 24 months with ≥2 doses of influenza vaccine (56.6%)
and the combined 7-vaccine series
††
(68.5%).
TABLE 1
Estimated vaccination coverage by age 24 months* among children born during 2013–2016
for selected vaccines and doses — National Immunization Survey-Child, United States,
2014–2018
Vaccine/Dose
% (95% CI)
Birth years†
Difference (2013–2014) to (2015–2016)
2013–2014
2015–2016
DTaP§
≥3 doses
93.6 (93.0 to 94.2)
93.8 (93.1 to 94.5)
0.2 (−0.7 to 1.1)
≥4 doses
80.6 (79.7 to 81.6)
80.3 (79.0 to 81.5)
−0.4 (−1.9 to 1.2)
Poliovirus (≥3 doses)
91.7 (91.0 to 92.4)
92.7 (92.0 to 93.4)
1.0 (0.0 to 2.0)
MMR (≥1 dose)¶
90.0 (89.3 to 90.7)
90.4 (89.5 to 91.2)
0.3 (−0.8 to 1.5)
Hib**
Primary series
92.7 (92.1 to 93.3)
92.7 (91.8 to 93.5)
0.0 (−1.1 to 1.0)
Full series
80.2 (79.3 to 81.1)
79.6 (78.3 to 80.9)
−0.6 (−2.1 to 1.0)
HepB
Birth dose††
71.8 (70.7 to 72.8)
75.0 (73.7 to 76.2)
3.2 (1.6 to 4.9)§§
≥3 doses
90.9 (90.2 to 91.6)
91.0 (90.2 to 91.9)
0.1 (−1.0 to 1.2)
Varicella (≥1 dose)¶
89.3 (88.6 to 90.1)
90.0 (89.1 to 90.9)
0.7 (−0.5 to 1.8)
PCV
≥3 doses
91.9 (91.2 to 92.5)
92.0 (91.1 to 92.8)
0.1 (−1.0 to 1.2)
≥4 doses
81.5 (80.6 to 82.4)
81.0 (79.8 to 82.3)
−0.4 (−2.0 to 1.1)
HepA
≥1 dose
83.2 (82.4 to 84.1)
84.7 (83.6 to 85.8)
1.5 (0.1 to 2.9)§§
≥2 doses (by 35 months)
74.0 (72.8 to 75.3)
76.6 (74.7 to 78.4)
2.6 (0.4 to 4.8)§§
Rotavirus (by 8 months)¶¶
72.4 (71.3 to 73.4)
73.6 (72.2 to 74.9)
1.2 (−0.5 to 2.9)
Influenza (≥2 doses)***
53.0 (51.9 to 54.1)
56.6 (55.2 to 58.0)
3.6 (1.8 to 5.4)§§
Combined 7-vaccine series†††
68.4 (67.3 to 69.5)
68.5 (67.1 to 69.9)
0.1 (−1.7 to 1.9)
No vaccinations
1.1 (1.0 to 1.3)
1.3 (1.1 to 1.5)
0.1 (−0.2 to 0.4)
Abbreviations: CI = confidence interval; DTaP = diphtheria, tetanus toxoids, and acellular
pertussis vaccine; HepA = hepatitis A vaccine; HepB = hepatitis B vaccine; Hib = Haemophilus
influenzae type b conjugate vaccine; MMR = measles, mumps, and rubella vaccine; PCV = pneumococcal
conjugate vaccine.
* Includes vaccinations received by age 24 months (before the day the child turns
24 months), except for the HepB birth dose, rotavirus vaccination, and ≥2 HepA doses
by 35 months. For all vaccines, except the HepB birth dose and rotavirus vaccination,
the Kaplan-Meier method was used to estimate vaccination coverage to account for children
whose vaccination history was ascertained before age 24 months (35 months for ≥2 HepA
doses).
† Data for the 2013 birth year are from survey years 2014, 2015, and 2016; data for
the 2014 birth year are from survey years 2015, 2016, and 2017; data for the 2015
birth year are from survey years 2016, 2017, and 2018; data for the 2016 birth year
are considered preliminary and come from survey years 2017 and 2018 (data from survey
year 2019 are not yet available).
§ Includes children who might have received diphtheria and tetanus toxoids vaccine
or diphtheria, tetanus toxoids, and pertussis vaccine.
¶ Includes children who might have received measles, mumps, rubella, and varicella
combination vaccine.
** 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.
§§ Statistically significantly different from 0 at p<0.05.
¶¶ Includes ≥2 doses of Rotarix monovalent rotavirus vaccine, or ≥3 doses of RotaTeq
pentavalent rotavirus vaccine. The maximum age for the final rotavirus dose is 8 months,
0 days.
*** Doses must be at least 24 days apart (4 weeks with a 4-day grace period).
††† The combined 7-vaccine series (4:3:1:3*:3:1:4) includes ≥4 doses of DTaP, ≥3 doses
of poliovirus vaccine, ≥1 dose of measles-containing vaccine, the full series of Hib
(≥3 or ≥4 doses, depending on product type), ≥3 doses of HepB, ≥1 dose of varicella
vaccine, and ≥4 doses of PCV.
Vaccination Coverage by Selected Characteristics and Geographic Location
For most of the vaccines assessed, uninsured children, and children with Medicaid
or other nonprivate insurance, had lower coverage than did privately insured children
(Table 2). Compared with privately insured children, coverage disparities were largest
among uninsured children, ranging from 7.8 percentage points for the HepB birth dose
to 33.8 percentage points for ≥2 doses of influenza vaccine. The proportion of children
who received no vaccinations was higher among uninsured children (7.4%) than among
those with private insurance (0.8%). Disparities were also observed for race/ethnicity
(Supplementary Table 1, https://stacks.cdc.gov/view/cdc/81681), poverty level (Supplementary
Table 2, https://stacks.cdc.gov/view/cdc/81682), and metropolitan statistical area
§§
(MSA) (Supplementary Table 2, https://stacks.cdc.gov/view/cdc/81682) but tended to
be smaller than those seen with health insurance status. Coverage varied widely by
state/local area for many vaccines (Supplementary Table 3, https://stacks.cdc.gov/view/cdc/81683).
Coverage with ≥1 dose of MMR was <90% in 20 states; only six states had coverage of
94% or higher (Figure).
TABLE 2
Estimated vaccination coverage by age 24 months* among children born during 2015–2016,
†
by selected vaccines and doses and health insurance status
§
— National Immunization Survey-Child, United States, 2016–2018
Vaccine/Dose
Health insurance status, % (95% CI)
Private only (referent) (n = 12,702)
Any Medicaid (n = 9,442)
Other insurance (n = 2,141)
Uninsured (n = 774)
DTaP¶
≥3 doses
96.9 (96.3–97.5)
91.8 (90.5–93.1)**
93.9 (92.2–95.3)**
80.6 (75.2–85.5)**
≥4 doses
87.1 (85.7–88.5)
75.8 (73.6–77.9)**
78.8 (75.4–82.0)**
59.8 (53.8–65.9)**
Poliovirus (≥3 doses)
96.1 (95.4–96.7)
90.7 (89.3–92.0)**
92.3 (90.4–94.0)**
79.3 (73.9–84.3)**
MMR (≥1 dose)††
93.7 (92.8–94.5)
88.6 (87.0–90.1)**
89.8 (87.6–91.8)**
73.2 (67.4–78.7)**
Hib§§
Primary series
95.7 (94.5–96.8)
90.7 (89.3–92.1)**
93.7 (91.9–95.1)
78.4 (72.8–83.5)**
Full series
85.5 (83.7–87.1)
75.9 (73.8–78.0)**
79.1 (75.8–82.1)**
58.1 (52.1–64.2)**
HepB
Birth dose¶¶
75.6 (73.9–77.2)
76.1 (74.0–78.1)
68.2 (64.3–71.9)**
67.8 (61.9–73.2)**
≥3 doses
93.0 (91.8–94.0)
90.0 (88.5–91.4)**
91.9 (89.9–93.6)
78.6 (73.3–83.5)**
Varicella (≥1 dose)††
93.2 (92.3–94.0)
88.6 (86.9–90.1)**
89.1 (86.8–91.2)**
70.3 (64.5–75.9)**
PCV
≥3 doses
94.9 (93.5–96.0)
90.3 (88.9–91.7)**
92.0 (90.1–93.7)**
77.2 (71.7–82.4)**
≥4 doses
87.3 (85.6–88.8)
76.8 (74.7–78.9)**
80.9 (77.7–83.9)**
62.5 (56.7–68.3)**
HepA
≥1 dose
87.5 (85.9–89.0)
83.7 (81.9–85.4)**
84.0 (81.2–86.6)**
65.5 (59.7–71.3)**
≥2 doses (by 35 months)
80.5 (77.9–83.1)
75.2 (72.2–78.0)**
76.8 (71.3–81.9)
48.2 (41.0–56.0)**
Rotavirus (by 8 months)***
83.5 (81.9–85.0)
65.9 (63.5–68.1)**
72.4 (68.5–76.0)**
59.8 (53.8–65.5)**
Influenza (≥2 doses)†††
68.5 (66.6–70.4)
48.2 (45.9–50.5)**
52.7 (48.6–56.9)**
34.7 (29.4–40.7)**
Combined 7-vaccine series§§§
75.4 (73.5–77.2)
64.3 (62.0–66.6)**
65.9 (62.1–69.6)**
46.7 (40.9–52.9)**
No vaccinations
0.8 (0.6–1.0)
1.2 (0.9–1.6)
1.8 (1.2–2.6)**
7.4 (4.7–10.7)**
Abbreviations: CI = confidence interval; DTaP = diphtheria, tetanus toxoids, and acellular
pertussis vaccine; HepA = hepatitis A vaccine; HepB = hepatitis B vaccine; Hib = Haemophilus
influenzae type b conjugate vaccine; MMR = measles, mumps, and rubella vaccine; PCV = pneumococcal
conjugate vaccine.
* Includes vaccinations received by age 24 months (before the day the child turns
24 months), except for the HepB birth dose, rotavirus vaccination, and ≥2 HepA doses
by 35 months. For all vaccines, except the HepB birth dose and rotavirus vaccination,
the Kaplan-Meier method was used to estimate vaccination coverage to account for children
whose vaccination history was ascertained before age 24 months (35 months for ≥2 HepA
doses).
† Data for the 2015 birth year are from survey years 2016, 2017, and 2018; data for
the 2016 birth year are considered preliminary and come from survey years 2017 and
2018 (data from survey year 2019 are not yet available).
§ Children’s health insurance status was reported by parent or guardian. “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.
¶ Includes children who might have received diphtheria and tetanus toxoids vaccine
or diphtheria, tetanus toxoids, and pertussis vaccine.
** Statistically significant (p<0.05) difference compared with the referent group.
†† Includes children who might have received measles, mumps, rubella, and varicella
combination vaccine.
§§ 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.
*** Includes ≥2 doses of Rotarix monovalent rotavirus vaccine (RV1), or ≥3 doses of
RotaTeq pentavalent rotavirus vaccine (RV5). The maximum age for the final rotavirus
dose is 8 months, 0 days.
††† Doses must be at least 24 days apart (4 weeks with a 4-day grace period).
§§§ The combined 7-vaccine series (4:3:1:3*:3:1:4) includes ≥4 doses of DTaP, ≥3 doses
of poliovirus vaccine, ≥1 dose of measles-containing vaccine, the full series of Hib
(≥3 or ≥4 doses, depending on product type), ≥3 doses of HepB, ≥1 dose of varicella
vaccine, and ≥4 doses of PCV.
FIGURE
Estimated coverage with ≥1 dose of MMR by age 24 months among children born 2015–2016*
— National Immunization Survey-Child, United States, 2016–2018
Abbreviations: DC = District of Columbia; MMR = measles, mumps, and rubella vaccine.
* Data for the 2015 birth year are from survey years 2016, 2017, and 2018; data for
the 2016 birth year are considered preliminary and come from survey years 2017 and
2018 (data from survey year 2019 are not yet available).
The figure is a map of the United States showing the estimated coverage with ≥1 dose
of MMR by age 24 months among children born 2015–2016, using data from the National
Immunization Survey-Child from 2016 to 2018.
Trends in Vaccination Coverage
Vaccination coverage was stable by single birth year from 2011 through 2016 (https://www.cdc.gov/vaccines/imz-managers/coverage/childvaxview/pubs-presentations/NIS-child-vac-coverage-estimates-2014-2018-tables.html#supp-figure-01),
except for an increase in ≥2 doses of HepA by age 35 months from 71.1% (2011) to 76.6%
(2016). The proportion of children that received no vaccinations by age 24 months
increased slightly across birth years 2011 through 2016, with an estimated change
per year of 0.09 percentage points (https://www.cdc.gov/vaccines/imz-managers/coverage/childvaxview/pubs-presentations/NIS-child-vac-coverage-estimates-2014-2018-tables.html#supp-figure-02).
Only 1.3% of children born in 2015 and 2016 received no vaccinations (Table 1).
Discussion
Vaccination coverage by the second birthday among children born during 2015–2016 remained
high, with small increases in coverage with hepatitis A and B and influenza vaccines;
only 1.3% of children received no vaccinations. However, several opportunities for
improvement were apparent. Coverage was lower for children without private health
insurance, especially those with no insurance, as well as those living below the poverty
level and in more rural areas. Vaccination coverage also varied by state, with 20
states having MMR coverage <90%. Coverage with ≥2 doses of influenza vaccine was the
lowest among all recommended childhood vaccines.
The importance of achieving and sustaining high vaccination coverage across all communities
is illustrated by the 22 measles outbreaks occurring in the United States in 2019,
with 1,249 measles cases identified during January 1–October 1, 2019 (
3
). Most cases have been among persons who were not vaccinated against measles. Pockets
of low vaccination coverage, because of lack of access to vaccination services or
to hesitancy resulting from the spread of inaccurate information about vaccines, increase
the likelihood of a measles outbreak. Strategies are needed to increase access to
vaccination services, identify communities at risk, and implement initiatives to counter
inaccurate vaccine information (
4
).
Lower vaccination coverage among children who are uninsured, insured by Medicaid or
other nonprivate insurance, living below the poverty level, and living in rural areas
suggests challenges with access to affordable vaccinations or optimal vaccination
services. Uninsured children are eligible for vaccine at no cost through the Vaccines
for Children
¶¶
program, but efforts to promote the program might not be reaching this population
and therefore might need to be modified. Targeted programs to address logistical issues
such as expanded office hours and transportation to vaccination appointments could
facilitate access to vaccination services, regardless of the child’s type of insurance.
Providers need to use every patient encounter to screen for and offer vaccinations.
An analysis of NIS-Child data for children born during 2005–2015 found that disparities
in coverage with ≥4 doses of diphtheria, tetanus toxoids, and acellular pertussis
vaccine (DTaP) for those with Medicaid compared with those with private health insurance
could have been reduced by 42% had opportunities for receipt of the fourth DTaP dose
not been missed during visits when other vaccinations were received (
5
).
The transition to reporting by birth year rather than by survey year more directly
assesses recent changes in vaccination coverage and provides more interpretable estimates
and more accurate comparisons to evaluate immunization information systems (
2
,
6
,
7
). With a standard age at assessment (e.g., 24 months), estimates by birth year might
be slightly lower for some vaccines than were estimates by survey year, which on average,
assessed vaccination by age 27.5 months. Trends in vaccination coverage by birth year
and survey year are similar (
8
). Other changes include addition of assessment of ≥2 HepA doses by age 35 months
to better reflect current ACIP recommendations and the addition of vaccination with
2 doses of influenza vaccine by age 24 months.***
The findings in this report are subject to at least two limitations. First, as with
previous NIS-Child estimates by survey year, vaccination coverage estimates by birth
year might be biased because of an incomplete sample frame, nonresponse, and underascertainment
of vaccination (
6
). No evidence for change in survey accuracy from 2017 to 2018 was detected. Second,
starting in 2018, the NIS-Child sample was drawn only from cellular telephone numbers.
Vaccination coverage trends should thus be viewed with caution, although the effect
of dropping the landline sample is likely small.
Improvements in childhood vaccination coverage will require that parents and other
caregivers have access to vaccination providers and believe in the safety and effectiveness
of vaccines. Increased opportunity for vaccination can be facilitated through expanded
access to health insurance, greater promotion of available vaccines through the Vaccines
for Children program, and solutions to logistical challenges such as transportation,
child care, and time off from work. Providers can improve vaccination coverage overall
and reduce disparities by administering all recommended vaccines during office visits.
Compelling and accessible educational materials, combined with effective techniques
for providers to use when discussing vaccination, can be used to counter inaccurate
claims and communicate the value of vaccines in protecting the health of children
(
9
). In addition, actionable data at a local level are needed so that interventions
can be targeted to areas at risk for outbreaks of measles and other vaccine-preventable
diseases. More immunization information systems will contribute to this effort because
they streamline their data collection processes and improve data quality (
10
).
†††
Given low survey response rates, CDC is working to better assess accuracy of NIS-Child
vaccination coverage estimates, evaluate new survey approaches (e.g., switching to
an address-based sample frame), and integrate data from immunization information systems
and, potentially, other data sources (
7
).
Summary
What is already known about this topic?
The Advisory Committee on Immunization Practices recommends that children be vaccinated
against 14 potentially serious illnesses before age 24 months.
What is added by this report?
Among children born in 2015 and 2016, coverage was high and stable for most vaccines.
There were sociodemographic disparities in coverage, especially by health insurance
status. The proportion of completely unvaccinated children remained small.
What are the implications for public health practice?
Coverage can be improved with increased access to providers and health insurance,
administration of all recommended vaccines during office visits, and more effective
patient education about vaccine safety and efficacy. Actionable local level data are
a priority for creating targeted interventions to prevent outbreaks of measles and
other vaccine-preventable diseases.