Vaccination Coverage Among Children in Kindergarten — United States, 2013–14 School Year

Ranee Seither, MPH1, Svetlana Masalovich, MS2, Cynthia L Knighton1, Jenelle Mellerson, MPH2, James A. Singleton, PhD1, Stacie M. Greby, DVM1 (Author affiliations at end of text)

State and local vaccination requirements for school entry are implemented to maintain high vaccination coverage and protect schoolchildren from vaccine-preventable diseases (1). Each year, to assess state and national vaccination coverage and exemption levels among kindergartners, CDC analyzes school vaccination data collected by federally funded state, local, and territorial immunization programs. This report describes vaccination coverage in 49 states and the District of Columbia (DC) and vaccination exemption rates in 46 states and DC for children enrolled in kindergarten during the 2013–14 school year. Median vaccination coverage was 94.7% for 2 doses of measles, mumps, and rubella (MMR) vaccine; 95.0% for varying local requirements for diphtheria, tetanus toxoid, and acellular pertussis (DTaP) vaccine; and 93.3% for 2 doses of varicella vaccine among those states with a 2-dose requirement. The median total exemption rate was 1.8%. High exemption levels and suboptimal vaccination coverage leave children vulnerable to vaccine-preventable diseases. Although vaccination coverage among kindergartners for the majority of reporting states was at or near the 95% national Healthy People 2020 targets for 4 doses of DTaP, 2 doses of MMR, and 2 doses of varicella vaccine (2), low vaccination coverage and high exemption levels can cluster within communities.* Immunization programs might have access to school vaccination coverage and exemption rates at a local level for counties, school districts, or schools that can identify areas where children are more vulnerable to vaccine-preventable diseases. Health promotion efforts in these local areas can be used to help parents understand the risks for vaccine-preventable diseases and the protection that vaccinations provide to their children.

Federally funded immunization programs assess vaccination coverage among children entering kindergarten each school year. Health departments, school nurses, or school personnel assess the vaccination and exemption status, as defined by state and local school requirements, of a census or sample of kindergartners enrolled in public and private schools. Among the 49 states and DC reporting vaccination coverage data, 42 used their immunization information system (IIS) as at least one source of data for their school assessment. The type of school survey varied among the 49 states and DC reporting either vaccination coverage or exemption: 38 reported using a census of kindergartners; nine a sample of schools, kindergartners, or both; one a voluntary response of schools; and two a mix of methods. Two states used a sample to collect vaccination coverage data and a census to collect exemption data. Four states changed their type of survey from the previous school year.† Data from the public and private school vaccination assessments were aggregated by state and DC immunization programs and sent to CDC.§ Vaccination coverage data were provided for 4,252,368 kindergartners included in reports from 49 states and DC, and exemption data were provided for 3,902,571 kindergartners included in reports from 46 states and DC.

All estimates of coverage and exemption rates were adjusted based on the type of survey conducted and response rates, using data aggregated at school or county level as appropriate and available, unless otherwise noted.¶ Vaccination requirements for school entry, as reported to CDC by the federally funded immunization programs, varied.** Kindergartners were considered up-to-date for any single vaccine if they had received all of the doses of that vaccine required for school entry in their jurisdiction. Nine states considered kindergartners up-to-date only if they had received all of the doses for all vaccines required for school entry in their jurisdiction.†† Of the 49 states and DC reporting vaccination coverage, 13 met CDC standards for school assessment methods in 2013–14.§§

Among the 49 states and DC that reported 2013–14 school vaccination coverage, median 2-dose MMR vaccination coverage was 94.7% (range = 81.7% in Colorado to ≥99.7% in Mississippi); 23 reported coverage ≥95% (Table 1), and eight reported coverage <90% (Table 1, Figure). Median local requirement for DTaP vaccination coverage was 95.0% (range = 80.9% in Colorado to ≥99.7% in Mississippi); 25 reported coverage ≥95%. Median 2-dose varicella vaccination coverage among the 36 states and DC requiring and reporting 2 doses was 93.3% (range = 81.7% in Colorado to ≥99.7% in Mississippi); nine reported coverage ≥95%.

Among the 46 states plus DC reporting 2013–14 school vaccination exemption data, the percentage of kindergartners with an exemption was <1% for eight states and ≥4% for 11 states (range = <0.1% in Mississippi to 7.1% in Oregon), with a median of 1.8% (Figure; Table 2). Two states reported increases over the previous school year of ≥1.0 percentage point: Kansas (1.5 percentage points) and Maine (1.2 percentage points). One state reported a decrease of ≥1.0 percentage points: West Virginia (1.0 percentage point). Where reported separately, the median rate of medical exemptions was 0.2% (range = <0.1% in eight states [Alabama, Arkansas, Colorado, Delaware, Georgia, Hawaii, Mississippi, and Nevada] to 1.2% [Alaska and Washington]). Where allowed and reported separately, the median rate of nonmedical exemptions was 1.7% (range = 0.4% in Virginia and DC to 7.0% in Oregon).

Discussion

Most federally funded immunization programs continued to report high vaccination coverage and stable exemption rates among kindergartners during the 2013–14 school year compared with the 2012–13 school year, although 26 states and DC did not report meeting the Healthy People 2020 target of 95% coverage for 2 doses of MMR vaccine. Although high levels of vaccination coverage by state are reassuring, vaccination exemptions have been shown to cluster geographically (3,4), so vaccine-preventable disease outbreaks can still occur where unvaccinated persons cluster in schools and communities (5).

School vaccination coverage assessment is used to assess state or local-level school vaccination requirements. Eighteen states provide local-level data online, helping to strengthen immunization programs, guide vaccination policies, and inform the public.¶¶ Local-level school vaccination and exemption data can be used by health departments and schools to focus vaccine-specific interventions and health communication efforts in a school or local area with documented low vaccination coverage or high exemption rates. Where expanded health communication strategies or other interventions are implemented, continued assessment and reporting can be used to facilitate program improvement.

To be most effective, accurate and reliable estimates of vaccination coverage and exemptions are needed. Use of appropriate sampling and survey methods can improve the usefulness of data for local use and comparability of estimates across school, local area, state, and national levels to accurately assess vaccination coverage and track progress toward Healthy People 2020 targets.

School vaccination coverage reporting can be labor intensive, involving education systems at the start of the school year, when they are busiest. School vaccination assessment systems can be linked to an IIS, allowing schools to review the vaccination status of individual children. During the 2013–14 school year, 36 of the 50 states and DC reported that they allowed schools to obtain provider-reported vaccination data from their IIS, and 14 reported using an IIS algorithm to determine vaccination status for at least some of the students in their school vaccination assessment. An example of how an IIS can be used to simplify school vaccination assessment is Tennessee's Immunization Certificate Validation Tool, which compares a child's record in the state IIS against Tennessee vaccination requirements for pre-school or school attendance, allowing vaccination providers and school nurses to quickly assess a schoolchild's vaccination status. It produces an official Tennessee Immunization Certificate or a detailed failure report. Tools linking school vaccination assessment systems to IIS data provide access to provider-reported information, reduce the documentation burden on parents and vaccination providers, and lessen the workload required by the assessment process on schools and health departments.

The findings in this report are subject to at least six limitations. First, not every state reported vaccination and exemption data. Second, vaccination and exemption status reflected the child's status at the time of assessment. Reports might not be updated when parents submit amended school vaccination records after the required vaccines are received or an exemption is claimed. Third, a child with an exemption is not necessarily unvaccinated. More than 99% of the 2008–2009 birth cohorts who became kindergartners in 2013–14 received at least one vaccine in early childhood (6). An exemption might be provided for all vaccines even if a child missed a single vaccine dose or vaccine, or different exemptions might be provided for different vaccinations. A parent or guardian might choose to complete the required exemption paperwork if that is more convenient than having a child vaccinated or documenting a kindergartner's vaccination history at school enrollment, which might be the reason for up to 25% of nonmedical exemptions (7–9).*** Fourth, methodology varied by reporting program or between school years for the same program. Methods and times for data collection differed, as did requirements for vaccinations and exemptions. Fifth, some programs (Delaware, Houston, Virginia, and Puerto Rico) were unable to provide detailed information needed to weight and analyze their data in the most statistically appropriate way, limiting the validity of their reported estimates. Finally, in adjusting data collected using school or student census methods to account for nonresponse, it was assumed that nonresponders and responders of the same school type had similar vaccination coverage and exemption rates.

State and local school vaccination assessments might detect local areas of undervaccination where disease transmission is more likely to occur. These data are most useful when the assessment is accurate and reliable. Use of statistically appropriate sampling methods and access to provider-reported vaccination data in an IIS can streamline the data collection process while providing accurate local-level data, allowing health departments to appropriately direct vaccination efforts during outbreaks of vaccine-preventable disease and identify schools and communities potentially at higher risk for vaccine-preventable disease transmission. Accurate local-level data can also be used by health departments and schools to focus health communication and other interventions that protect children and the community at large against vaccine-preventable diseases.

Acknowledgments

Seth A. Meador, Leidos; Amanda R. Bryant, Immunization Services Division, National Center for Immunization and Respiratory Diseases, CDC.

References

Orenstein W, Hinman A. The immunization system in the United States: the role of school immunization laws. Vaccine 1999;17(Suppl 3):S19–24. US Department of Health and Human Services. Healthy people 2020: immunization and infectious diseases. Washington, DC: US Department of Health and Human Services; 2010. Available at http://www.healthypeople.gov/2020/topicsobjectives2020/overview.aspx?topicid=23. Sugerman D, Barskey AE, Delea MG, et al. Measles outbreak in a highly vaccinated population, San Diego, 2008: role of the intentionally undervaccinated. Pediatrics 2010;125:747–55. Omer SB, Enger KS, Moulton LH, Halsey NA, Stokley S, Salmon DA. Geographic clustering of nonmedical exemptions to school immunization requirements and associations with geographic clustering of pertussis. Am J Epidemiol 2008;168:1389–96. Gay N. The theory of measles elimination: implications for the design of elimination strategies. J Infect Dis 2004;189(Suppl 1):S27–35. CDC. National, state, and local area vaccination coverage among children aged 19–35 months—United States, 2012. MMWR 2013;62:733–40. Rota JS, Salmon DA, Rodewald LE, Chen RT, Hibbs BF, Gangarosa EJ. Processes for obtaining nonmedical exemptions to state immunization laws. Am J Public Health 2001;91:645–8. Blank N, Caplan A, Constable C. Exempting schoolchildren from immunizations: states with few barriers had highest rates of nonmedical exemptions. Health Aff 2013;32:1282–90. Luthy KE, Beskstrand RL, Callister LC, Cahoon S. Reasons parents exempt children from receiving immunizations. J Sch Nurs 2012;28:153–60.

What is already known on this topic? To protect school children from vaccine-preventable disease, annual school vaccination assessments indicate vaccination coverage and exemptions from state vaccination requirements. Although state vaccination coverage is high and exemptions are low, undervaccination and exemptions cluster at a local level, where vaccine-preventable diseases might be easily transmitted. What is added by this report? In 49 states and the District of Columbia (DC), median vaccination coverage for three vaccines was 94.7% for the measles, mumps, and rubella vaccine, 95.0% for varying local requirements for the diphtheria, tetanus toxoid, and acellular pertussis vaccine, and 93.3% for varicella vaccine among states with a 2-dose requirement. Of the 49 states and DC reporting vaccination coverage estimates, 27 did not report meeting the Healthy People 2020 target of 95% coverage for 2 doses of measles, mumps, and rubella vaccine. Median exemption levels continue to be low overall (1.8%). What are the implications for public health practice? Local data are essential to controlling the spread of vaccine-preventable disease. Accurate and reliable school vaccination assessments can provide a unique opportunity for school and health departments to identify local areas of undervaccination, even at a school or classroom level, where the potential for disease transmission is higher. Health departments can use these data to identify schools and communities at higher risk for outbreaks and provide health communication interventions to protect school children and the community at large against vaccine-preventable diseases.

FIGURE. Estimated percentage of children enrolled in kindergarten who have been exempted from receiving one or more vaccines* and with <90% coverage with 2 doses of measles, mumps, and rubella (MMR) vaccine — United States, 2013–14 school year Alternate Text: The figure above is a map of the United States showing the estimated percentage of children enrolled in kindergarten who have been exempted from receiving one or more vaccines and with <90% coverage with 2 doses of measles, mumps, and rubella (MMR) vaccine in the United States during the 2013–14 school year. Among the 49 states and DC that reported 2013–14 school vaccination coverage, median 2-dose MMR vaccination coverage was 94.7% (range = 81.7% in Colorado to ≥99.7% in Mississippi); 23 reported coverage ≥95%, and eight reported coverage <90%. The percentage of kindergartners with an exemption was <1% for eight states and ≥4% for 11 states (range = <0.1% in Mississippi to 7.1% in Oregon), with a median of 1.8%.

TABLE 1. Estimated vaccination coverage,* by state/area and vaccination among children enrolled in kindergarten — United States, 2013–14 school year State/Area Kindergarten population† Total surveyed Proportion surveyed (%) Type of survey conducted§ MMR¶ DTaP** Varicella 1 dose 2 doses (%) (%) (%) (%) Alabama†† 76,927 76,927 100.0 Census ≥92.0 ≥92.0 ≥92.0 NReq Alaska§§ 10,222 946 9.3 Stratified 2-stage cluster sample 94.4 96.0 92.5 Arizona 89,606 85,861 95.8 Census 93.9 94.3 96.4 NReq Arkansas 42,649 41,068 96.3 Census 86.5 83.3 85.4 California¶¶ 548,606 533,680 97.3 Census 92.3 92.2 95.3 NReq Colorado 69,904 350 0.5 Random sample 81.7 80.9 81.7 Connecticut†† 40,978 40,978 100.0 Census 96.9 97.0 96.7 Delaware 11,997 1458 12.2 Stratified 2-stage cluster sample ≥96.4 ≥96.4 ≥96.4 District of Columbia†† 7,856 7,856 100.0 Census 89.0 88.7 88.8 Florida††*** 233,797 233,797 100.0 Census ≥93.2 ≥93.2 ≥93.2 Georgia†† 143,988 143,988 100.0 Census ≥94.0 ≥94.0 ≥94.0 Hawaii 20,056 1,074 5.4 Stratified 2-stage cluster sample 98.7 99.0 99.2 NReq Idaho†† 23,934 23,934 100.0 Census 88.2 88.0 86.5 Illinois†† 163,316 163,316 100.0 Census 94.7 95.0 96.6 NReq Indiana†† 87,193 61,336 70.3 Census 92.9 81.8 90.2 Iowa 43,728 41,349 94.6 Census ≥91.0 ≥91.0 ≥91.0 Kansas§§¶¶ 41,107 11,931 29.0 Stratified 1-stage sample (Public), Census (Private) 86.9 87.6 85.5 Kentucky†† 57,857 57,857 100.0 Census 92.6 93.9 91.9 Louisiana†† 63,976 63,976 100.0 Census 96.8 98.3 96.1 Maine 15,441 12,716 82.4 Census 89.9 94.4 93.8 NReq Maryland¶¶ 75,659 73,349 96.9 Census 97.6 99.0 99.0 NReq Massachusetts 79,894 78,188 97.9 Census 95.1 93.0 93.9 Michigan†† 120,297 120,297 100.0 Census 97.5 94.8 93.0 Minnesota¶¶ 72,087 70,972 98.5 Census 93.4 96.6 92.6 Mississippi†† 45,719 45,719 100.0 Census ≥99.7 ≥99.7 ≥99.7 Missouri†† 78,140 78,140 100.0 Census 95.5 96.0 94.6 Montana 12,855 12,259 95.4 Census 93.7 94.8 NReq Nebraska¶¶ 27,000 26,282 97.3 Census 96.6 96.8 94.9 Nevada 35,782 1,114 3.1 Stratified 2-stage cluster sample 95.6 94.4 93.6 New Hampshire†† 13,240 13,240 100.0 Census ≥94.7 ≥94.7 ≥94.7 New Jersey 123,085 117,477 95.4 Census ≥96.8 ≥96.8 ≥96.8 NReq New Mexico¶¶ 30,725 830 2.7 Stratified 2-stage cluster sample 95.9 97.4 93.4 New York¶¶ 240,318 240,318 100.0 Census 96.8 98.1 98.2 NReq North Carolina 126,084 123,192 97.7 Census 98.8 98.7 99.7 NReq North Dakota 9,780 9,397 96.1 Census (public)

Stratified 2-stage cluster sample (private) 90.0 90.2 89.4 Ohio 150,000 138,820 92.5 Census 96.2 96.1 95.7 Oklahoma 57,377 40,929 71.3 Voluntary response 96.4 96.1 98.0 Oregon†† 47,649 47,649 100.0 Census 93.2 93.3 94.3 NReq Pennsylvania††¶¶ 151,253 151,253 100.0 Census 85.3 NReq††† 84.0 Rhode Island 11,521 11,421 99.1 Census 95.1 96.0 94.7 South Carolina 61,661 6,771 11.0 1-stage stratified sample 96.8 97.3 94.4 NReq South Dakota†† 12,566 12,566 100.0 Census 96.6 96.7 95.3 Tennessee 80,212 80,079 99.8 Census ≥94.9 ≥94.9 ≥94.9 Texas§§ (including Houston) 409,255 397,262 97.1 Census 97.5 97.2 97.2 Houston, Texas 36,254 1,856 5.1 2-stage cluster sample, nonrandom schools selection 91.9 90.4 90.4

TABLE 1. (Continued) Estimated vaccination coverage,* by state/area and vaccination among children enrolled in kindergarten — United States, 2013–14 school year State/Area Kindergarten population† Total surveyed Proportion surveyed (%) Type of survey conducted§ MMR¶ DTaP** Varicella 1 dose 2 doses (%) (%) (%) (%) Utah†† 54,779 54,779 100.0 Census 98.5 98.1 99.6 NReq Vermont†† 6,771 6,771 100.0 Census 91.2 92.0 89.4 Virginia 105,692 4,287 4.1 2-stage cluster sample 93.1 98.3 91.3 Washington 89,165 78,924 88.5 Census 89.7 90.3 88.4 West Virginia 22,814 19,313 84.7 Census 96.1 96.5 95.5 Wisconsin¶¶ 71,363 1,990 2.8 Stratified 2-stage cluster sample 92.6 96.3 91.2 Wyoming NA NA NA Not conducted Median§§§ 94.7 95.0 96.6 93.3 American Samoa NA NA NA Not conducted Guam 2,935 1,235 42.1 Stratified 2-stage cluster sample 88.4 92.8 NReq Marshall Islands NA NA NA Not conducted Micronesia NA NA NA Not conducted N. Mariana Islands 725 725 100.0 Census 96.0 94.3 92.3 Palau 402 NA NA Not conducted NReq Puerto Rico 39,170 6,789 17.3 Stratified 2-stage cluster sample 94.3 91.3 91.4 U.S. Virgin Islands 1,612 731 45.3 Stratified 2-stage cluster sample 90.5 91.0 87.9

TABLE 2. Estimated number and percentage* of children enrolled in kindergarten with exemption(s) from vaccination, by state/area and type of exemption — United States, 2013–14 school year State/Area Medical exemptions† Nonmedical exemptions† Total exemptions† No. of religious exemptions No. of philosophic exemptions Total

no. % Total

no. 2013–14

(%) 2012–13

(%) Percentage point difference No. % Alabama 70 <0.1 447 § 447 0.6 517 0.7 0.7 0.0 Alaska 119 1.2 421 § 421 4.1 539 5.3 5.6 -0.3 Arizona 175 0.2 ¶ 4,195 4,195 4.7 4,370 4.9 4.2 0.7 Arkansas 24 <0.1 135 333 468 1.1 493 1.2 1.1 0.1 California 1017 0.2 †† 17,253 17,253 3.1 18,270 3.3 3.0 0.3 Colorado 0 <0.1 195 3,097 3,292 4.6 3,291 4.6 4.3 0.3 Connecticut 128 0.3 670 § 670 1.6 725 1.9 1.7 0.2 Delaware 9 <0.1 83 § 83 0.7 92 0.8 0.7 0.1 District of Columbia 85 1.1 33 § 33 0.4 118 1.5 1.6 -0.1 Florida 772 0.3 3,991 § 3,991 1.7 4,763 2.0 1.8 0.2 Georgia 143 <0.1 2,420 § 2,420 1.7 2,563 1.8 2.3 -0.5 Hawaii 0 <0.1 634 § 634 3.2 634 3.2 2.5 0.7 Idaho 89 0.4 147 1,304 1,451 6.1 1,540 6.4 5.9 0.5 Illinois** NA NA NA NA 6.1 NA Indiana 348 0.4 727 § 727 0.8 1,075 1.2 1.3 -0.1 Iowa 205 0.5 521 § 521 1.2 726 1.7 1.7 0.0 Kansas 213 0.8 527 § 527 1.9 739 2.6 1.1 1.5 Kentucky 148 0.3 357 § 357 0.6 505 0.9 0.7 0.2 Louisiana 83 0.1 28 394 422 0.7 505 0.8 0.7 0.1 Maine 56 0.4 30 766 796 5.2 852 5.5 4.3 1.2 Maryland 244 0.3 513 § 513 0.7 758 1.0 1.0 0.0 Massachusetts 332 0.4 860 § 860 1.1 1,192 1.5 1.5 0.0 Michigan 573 0.5 1,250 5,226 6,476 5.4 7,049 5.9 5.9 0.0 Minnesota** NA NA NA NA 1.6 NA Mississippi 17 <0.1 ¶ § NA 17 <0.1 <0.1 0.0 Missouri** NA NA NA NA 1.8 NA Montana 36 0.3 426 § 426 3.3 463 3.6 3.5 0.1 Nebraska 158 0.6 307 § 307 1.1 465 1.7 1.7 0.0 Nevada 7 <0.1 724 § 724 2.0 731 2.0 2.5 -0.5 New Hampshire 49 0.4 328 § 328 2.5 377 2.8 2.5 0.3 New Jersey 262 0.2 1,741 § 1,741 1.4 2,003 1.6 1.4 0.2 New Mexico 72 0.2 277 § 277 0.9 349 1.1 0.4 0.7 New York 302 0.1 1,547 § 1,547 0.6 1,849 0.8 0.7 0.1 North Carolina 161 0.1 1,105 § 1,105 0.9 1,266 1.0 0.8 0.2 North Dakota 32 0.3 45 185 230 2.3 262 2.7 1.8 0.9 Ohio 369 0.2 †† †† 2,681 1.8 3,050 2.0 2.0 0.0 Oklahoma 73 0.1 221 586 808 1.4 880 1.5 1.3 0.2 Oregon 62 0.1 3,331 †† 3,331 7.0 3,393 7.1 6.5 0.6 Pennsylvania 510 0.3 1,133 1,419 2,552 1.7 3,062 2.0 2.0 0.0 Rhode Island 33 0.3 81 § 81 0.7 114 1.0 1.1 -0.1 South Carolina§§ 83 0.1 772 § 772 1.2 855 1.4 NA NA South Dakota§§ 21 0.2 199 § 199 1.6 220 1.8 1.8 0.0 Tennessee 132 0.2 773 § 773 1.0 906 1.1 1.2 -0.1 Texas (including Houston) 2,266 0.6 †† †† 5,536 1.4 7,803 1.9 1.7 0.2 Houston 979 0.3 NA NA NA 979 0.3 0.9 -0.6