Introduction

State and local school vaccination requirements serve to protect students against vaccine-preventable diseases.^[1] This report summarizes data collected for the 2020–21 school year by state and local immunization programs* on vaccination coverage among children in kindergarten in 47 states and the District of Columbia (DC), exemptions for kindergartners in 48 states and DC, and provisional enrollment or grace period status for kindergartners in 28 states. Vaccination coverage^† nationally was 93.9% for 2 doses of measles, mumps, and rubella vaccine (MMR); 93.6% for the state-required number of doses of diphtheria, tetanus, and acellular pertussis vaccine (DTaP); and 93.6% for the state-required doses of varicella vaccine. Compared with the 2019–20 school year, vaccination coverage decreased by approximately one percentage point for all vaccines. Although 2.2% of kindergartners had an exemption from at least one vaccine,^§ an additional 3.9% who did not have a vaccine exemption were not up to date for MMR. The COVID-19 pandemic affected schools' vaccination requirement and provisional enrollment policies, documentation, and assessment activities. As schools continue to return to in-person learning, enforcement of vaccination policies and follow-up with undervaccinated students are important to improve vaccination coverage.

To meet state and local school entry requirements, parents submit children's vaccination or exemption documentation to schools, or schools obtain records from state immunization information systems. Federally funded immunization programs work with departments of education, school nurses, and other school personnel to assess vaccination and exemption status of children enrolled in public and private kindergartens and to report unweighted counts, aggregated by school type, to CDC via a web-based questionnaire in the Secure Access Management System, a federal, web-based system that gives authorized personnel secure access to public health applications operated by CDC. CDC uses these counts to produce state-level and national-level estimates of vaccination coverage. During the 2020–21 school year, 47 states and DC reported coverage for all state-required vaccines among public and private school kindergartners;^¶ 48 states and DC reported exemption data on public school kindergartners and 47 states and DC on private school kindergartners. Overall national and median vaccination coverage for the state-required number of doses of DTaP, MMR, and varicella vaccine are reported. Hepatitis B and poliovirus vaccination coverage, not included in this report, are available at SchoolVaxView.^[2] Twenty-eight states reported the number of kindergartners who were attending school under a grace period (attendance without proof of complete vaccination or exemption during a set interval) or provisional enrollment (school attendance while completing a catch-up vaccination schedule). Thirty states and DC reported the number of kindergartners who had no documentation of any vaccinations or exemptions. Seventeen states reported the number of kindergartners who were out of compliance; these kindergartners did not have complete documentation of having received all required vaccinations but were not eligible for provisional enrollment and did not have documented exemptions for the missing vaccinations. This measure includes those with no documentation at all. All counts were current as of the time of the assessment.** National estimates, medians, and summary measures include only U.S. states and DC. This activity was reviewed by CDC and was conducted consistent with applicable federal law and CDC policy.^††

Vaccination coverage and exemption estimates were adjusted according to survey type and response rate.^§§ National estimates measure coverage and exemptions among all kindergartners, whereas medians measure the midpoint of state-level coverage regardless of population size. During the 2020–21 school year, 3,520,205 children in 48 states and DC were reported by immunization programs as enrolled in kindergarten.^¶¶ Reported estimates are based on 3,187,569 of these kindergartners who were surveyed for vaccination coverage; 3,337,916 for exemptions; 2,467,326 for grace period and provisional enrollment; 1,799,190 for documentation; and 1,049,075 for compliance. Kindergarten enrollment reported by the 48 states and DC was approximately 10% lower than that reported for the 2019–20 school year by 48 states. Potentially achievable coverage with MMR, defined as the sum of the percentage of children who were up to date with 2 doses of MMR and those with no documented vaccination exemption but not up to date, was calculated for each state. Nonexempt students include those who were provisionally enrolled in kindergarten, in a grace period, or otherwise without documentation of complete vaccination. SAS software (version 9.4; SAS Institute) was used for all analyses.

Vaccination assessments varied by state because of differences in required vaccines and doses, vaccines assessed, methods of data collection, and data reported (Supplementary Table 1, https://stacks.cdc.gov/view/cdc/116354). Kindergartners were considered up to date for a given vaccine if they received all doses of that vaccine required for school entry,*** except in nine states^††† that reported kindergartners as up to date for any given vaccine only if they received all doses of all vaccines required for school entry. States were asked to report any COVID-19–related impact on kindergarten vaccination measurement and coverage.

Nationally, 2-dose MMR coverage was 93.9% (median = 93.7%; range = 78.9% [DC] to ≥98.9% [Mississippi]). Coverage ≥95% was reported by 16 states and <90% by 7 states and DC (Table). DTaP coverage was 93.6% (range = 78.5% [DC] to ≥98.9% [Mississippi]). Coverage ≥95% was reported by 16 states, and coverage <90% by eight states and DC. Varicella vaccine coverage nationally was 93.6% (range = 78.0% [DC] to ≥98.9% [Mississippi]), with 17 states reporting coverage ≥95% and nine states and DC reporting <90% coverage.

The percentage of kindergartners with an exemption for ≥1 required vaccines (not limited to MMR, DTaP, and varicella vaccines) was 2.2% in 2020–21 (range = 0.1% [Mississippi and New York] to 8.2% [Idaho]), similar to the 2.5% reported during the 2019–20 school year (Table). Nationally, 0.2% of kindergartners had a medical exemption and 1.9% had a nonmedical exemption (Supplementary Table 2, https://stacks.cdc.gov/view/cdc/116355). The percentage of kindergartners provisionally enrolled in kindergarten or within a grace period among the 28 states reporting these data was 2.0% (range = 0.1% [Hawaii] to 10.0% [Arkansas]) (Table).

Among states that reported data for both 2019–20 and 2020–21, MMR coverage and exemptions for ≥1 vaccines decreased in approximately 75% of states; grace period or provisional enrollment increased in 18 of the 28 states reporting this measure (Figure 1).

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FIGURE 1. Change in measles, mumps, and rubella vaccine coverage, any exemption, grace period or provisional enrollment, and no documentation* among kindergartners, by state — 47 states,† 2019–20 to 2020–21 school year

The proportion of students who were not fully vaccinated and not exempt increased in a majority of states. Among states reporting these measures in 2020–21, the proportion of kindergartners attending school with no documentation of required vaccinations or exemptions ranged from 0.1% (Pennsylvania and Virginia) to 8.3% (Maryland); the proportion out of compliance with school requirements ranged from 0.2% (Florida) to 16.6% (Indiana) (Table). Among the 33 states and DC with MMR coverage <95%, all but two could potentially achieve ≥95% MMR coverage if all nonexempt kindergartners who were within a grace period, provisionally enrolled, or out of compliance received vaccination (Figure 2).

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FIGURE 2. Potentially achievable coverage*,† with measles, mumps, and rubella vaccine 
among kindergartners, by state — 47 states§ and District of Columbia, 2020–21 school year

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*Federally funded immunization programs are located in 50 states and DC, five cities, and eight U.S territories and freely associated states (territories). Two cities reported data to CDC, which were also included in data submitted by their state. State-level data were used to calculate national estimates and medians. Immunization programs in territories reported vaccination coverage and exemptions; however, these data were not included in national calculations.
^†National and median vaccination coverage was determined using estimates for 47 states and DC; Alaska, Illinois, and West Virginia did not report school coverage data because of the impact of COVID-19 on data collection. Data from cities were included with their state data. Data from territories were not included in national and median calculations.
^§National and median exemption rates were determined using estimates for 48 states and DC; Colorado, Minnesota, and Missouri did not collect information on the number of kindergartners with an exemption but instead reported the number of exemptions for each vaccine, which could count some children more than once. For these states, the percentage of kindergartners exempt from the vaccine with the highest number of exemptions (the lower bound of the potential range of exemptions) was included in the national and median exemption rates. Washington was unable to deduplicate students with both religious and philosophical exemptions, so the nonmedical exemption type with the highest number of kindergartners (the lower bound of the potential range of nonmedical exemptions) was included in the national and median exemption rates for nonmedical exemptions. Illinois and West Virginia did not report school vaccine exemption data because of the impact of COVID-19 on data collection. Data from cities were included with their state data. Data from territories were not included in national estimates.
^¶Nine states reported coverage and exemption data for at least some homeschooled kindergartners. Alaska and North Dakota reported some homeschool data separately. California included data for students who attend virtual, partial, or full charter schools with some or all online instruction and students receiving individualized education program services who are medically unable to attend school in public school data. California also included data for homeschools with six or more students in private school data. Montana reported homeschooled students in public school data if the students also attend classes or extracurricular activities at a public school. New Mexico and Pennsylvania included all homeschooled students in public school data. Oregon reported data for students enrolled in exclusively online homeschool programs separately; online students of otherwise traditional public schools were included in public school data. South Carolina and Wisconsin include homeschooled students in their public and private school data if the students also attend classes, extracurricular activities, or have other contact with a school.
**Assessment date varied by state and area. Four states were assessed on the first day of school; 13 states were assessed by December 31; 17 states and DC were assessed by some other date, ranging from 30 days after admission to June 23, 2021; and 16 states were assessed on a rolling basis. Maryland ended data collection early because of COVID-19 response activities.
^††45 C.F.R. part 46.102(l)(2), 21 C.F.R. part 56; 42 U.S.C. Sect. 241(d); 5 U.S.C. Sect. 552a; 44 U.S.C. Sect. 3501 et seq.
^§§A majority of immunization programs that used census or voluntary response provided CDC with data aggregated at the state or local (city or territory) level. Coverage and exemption data based on a census or voluntary response were adjusted for nonresponse using the inverse of the response rate, stratified by school type (public, private, and homeschool, where available). Programs that used complex sample surveys provided CDC with deidentified data aggregated at the school or county level for weighted analysis. Weights were calculated to account for sample design and adjusted for nonresponse for data collected through complex sample design wherever possible.
^¶¶These totals are the summations of the kindergartners surveyed among programs reporting data for coverage, exemptions, grace periods, and provisional enrollment. Data from cities and territories were not included in these totals.
***All states required 2 doses of a measles-containing vaccine. Six states (Georgia, New Jersey, New York, North Carolina, Oregon, and Virginia) require only 1 dose of rubella vaccine. New Jersey and Oregon require only 1 dose of mumps vaccine, and mumps vaccine is not required in Iowa. Local DTaP requirements varied. Nebraska required 3 doses of DTaP, two states (Maryland and Wisconsin) required 4 doses, and all other states required 5 doses, unless dose 4 was administered on or after the fourth birthday. The reported coverage estimates represent the percentage of kindergartners with the state-required number of DTaP doses, except for Kentucky, which required 5 doses of DTaP by age 5 years but reported 4-dose coverage for kindergartners. Two states (Maryland and Nebraska) require only 3 doses of polio vaccine, all other states require 4 doses unless the last dose was given on or after the fourth birthday. Six states required 1 dose of varicella vaccine; 44 states and DC required 2 doses.
^†††Alabama, Florida, Georgia, Iowa, Mississippi, New Hampshire, New Jersey, Wisconsin, and Wyoming considered kindergartners up to date only if they had received all doses of all vaccines required for school entry.