Vaccination Coverage for Selected Vaccines and Exemption Rates Among Children in Kindergarten — United States, 2017–18 School Year

Abstract

State and local school vaccination requirements exist to ensure that students are protected from vaccine-preventable diseases ( 1 ). This report summarizes vaccination coverage and exemption estimates collected by state and local immunization programs* for children in kindergarten (kindergartners) in 49 states and the District of Columbia (DC) and kindergartners provisionally enrolled (attending school without complete vaccination or exemption while completing a catch-up vaccination schedule) or in a grace period (a set interval during which a student may be enrolled and attend school without proof of complete vaccination or exemption) for 28 states. Median vaccination coverage † was 95.1% for the state-required number of doses of diphtheria and tetanus toxoids, and acellular pertussis vaccine (DTaP); 94.3% for 2 doses of measles, mumps, and rubella vaccine (MMR); and 93.8% for 2 doses of varicella vaccine. The median percentage of kindergartners with an exemption from at least one vaccine § was 2.2%, and the median percentage provisionally enrolled or attending school during a grace period was 1.8%. Vaccination coverage among kindergartners remained high; however, schools can improve coverage by following up with students who are provisionally enrolled, in a grace period, or lacking complete documentation of required vaccinations. Federally funded immunization programs collaborate with departments of education, school nurses, and other school personnel to assess vaccination coverage and exemption status of children enrolled in public and private kindergartens. ¶ In accordance with state and local school entry requirements, parents and guardians submit children’s vaccination records or exemption forms to schools, or schools obtain records from state immunization information systems. During the 2017–18 school year, 49 states and DC reported coverage for all state-required vaccines and exemption data among public school kindergartners; 48 states and DC reported on private school kindergartners.** Median vaccination coverage for the state-required number of doses of DTaP, 2 doses of MMR, and 2 doses of varicella vaccine are reported. Coverage with hepatitis B and poliovirus vaccines, which are required in most states but not included in this report, are presented on SchoolVaxView ( 2 ). Twenty-eight states reported data on kindergartners who, at the time of assessment, attended school under a grace period or provisional enrollment. Immunization programs in U.S. territories also receive public funding for immunization and report vaccination coverage and exemptions to CDC; however, national medians and summary measures reported here include only the U.S. states and DC. Vaccination coverage and exemption estimates were adjusted according to survey type and response rates. †† During the 2017–18 school year, vaccination coverage data were reported for approximately 3,988,127 kindergartners, exemption data for approximately 3,634,631, and grace period and provisional enrollment data for approximately 2,825,691. §§ Potentially achievable coverage for MMR was calculated for each state as the percentage of students vaccinated with 2 doses of MMR plus the percentage without 2 doses of MMR and no documented vaccination exemption. Nonexempt students included those provisionally enrolled, in a grace period, or otherwise without documentation of vaccination. During the 2017–18 school year, vaccination assessments varied by immunization program because of differences in states’ required vaccines and doses, vaccines assessed, assessment methods, and data reported. Among the 49 states and DC reporting kindergarten vaccination data, 36 used a census; nine used a sample; three used a voluntary school response; and two used a mix of sampling methods. ¶¶ All states used the same methods to collect both vaccination coverage and exemption data except Alaska, Kansas, Virginia, and Wisconsin, where a sample was used for vaccination coverage data and a census for exemption data. Kindergartners were considered up to date and included in the coverage estimate for a given vaccine if they received all doses required for school entry,*** except in seven states ††† that considered kindergartners up to date only if they received all doses of all vaccines required for school entry. Reporting of varicella vaccination status among kindergartners with a history of varicella disease varied within and among states; some were reported as vaccinated against varicella and others as medically exempt. Among the 49 states and DC included in this analysis, median 2-dose MMR coverage was 94.3% (range = 81.3% [DC] to ≥99.4% [Mississippi]), 23 states reported coverage ≥95%, and three states and DC reported coverage <90% (Table 1). Median DTaP coverage was 95.1% (range = 79.7% [DC] to ≥99.4% [Mississippi]), 25 states reported coverage ≥95%, and three states and DC reported coverage <90%. Among the 41 states and DC that required and reported 2 doses of varicella vaccine, median coverage was 93.8% (range = 80.5% [DC] to ≥99.4% [Mississippi]), 17 states reported coverage ≥95%, and four states and DC reported coverage <90%. TABLE 1 Estimated vaccination coverage* for MMR, DTaP, and varicella vaccines among children enrolled in kindergarten, by vaccine and immunization program — United States and territories, 2017–18 school year Immunization program Kindergarten population† No. (%) surveyed Type of survey conducted§ Local data available online¶ MMR** DTaP†† Varicella 2 doses (%) 4 or 5 doses (%) 1 dose (%) 2 doses (%) Median§§ 94.3 95.1 96.2 93.8 Alabama¶¶ 57,245 57,245 (100.0) Census Yes ≥92.7 ≥92.7 ≥92.7 NReq Alaska***,††† 9,692 707 (7.3) Stratified 2-stage cluster sample No 91.6 91.1 NA 91.3 Arizona¶¶ 81,710 81,710 (100.0) Census Yes 93.4 93.5 96.2 NReq Arkansas§§§ 39,630 38,242 (96.5) Census (public), voluntary response (private) No 91.9 91.3 NA 91.6 California§§§ 574,702 564,121 (98.2) Census Yes 96.9 96.4 98.2 NReq Colorado¶¶ 65,718 65,718 (100.0) Census Yes 88.7 88.6 NA 87.7 Connecticut¶¶ 39,174 39,174 (100.0) Census No 96.5 96.5 NA 96.3 Delaware 10,988 1,053 (9.6) Stratified 2-stage cluster sample No 96.7 96.9 NA 96.7 District of Columbia¶¶ 8,205 8,205 (100.0) Census No 81.3 79.7 NA 80.5 Florida¶¶,*** 222,397 222,397 (100.0) Census Yes ≥93.7 ≥93.7 NA ≥93.7 Georgia¶¶ 131,459 131,459 (100.0) Census No ≥93.4 ≥93.4 NA ≥93.4 Hawaii 16,325 1,040 (6.4) Stratified 2-stage cluster sample No 95.6 95.4 96.2 NReq Idaho 22,553 22,458 (99.6) Census Yes 89.5 89.3 NA 88.6 Illinois¶¶ 144,858 144,858 (100.0) Census Yes 95.2 95.3 NA 94.8 Indiana 84,296 70,857 (84.1) Voluntary response Yes 90.4 94.3 NA 90.2 Iowa¶¶ 39,632 39,632 (100.0) Census Yes ≥93.0 ≥93.0 NA ≥93.0 Kansas***,†††,§§§ 38,484 8,728 (22.7) Stratified 2-stage cluster sample Yes 89.1 89.5 NA 88.3 Kentucky***,§§§ 55,152 50,538 (91.6) Census Yes 92.6 93.7 NA 91.7 Louisiana¶¶ 58,277 58,277 (100.0) Census Yes 96.1 97.7 NA 95.6 Maine 13,255 12,527 (94.5) Census Yes 94.3 95.3 96.5 NReq Maryland§§§ 68,528 67,747 (98.9) Census No 98.6 99.0 NA 98.6 Massachusetts¶¶,§§§ 63,377 63,377 (100.0) Census Yes 96.3 96.4 NA 96.0 Michigan¶¶ 119,028 119,028 (100.0) Census Yes 95.0 95.3 NA 94.7 Minnesota*** 69,807 67,372 (96.5) Census Yes 92.5 92.8 NA 92.2 Mississippi¶¶ 39,284 39,284 (100.0) Census Yes ≥99.4 ≥99.4 NA ≥99.4 Missouri¶¶ 73,113 73,113 (100.0) Census No 95.2 95.3 NA 95.0 Montana¶¶ 12,188 12,188 (100.0) Census No 93.2 92.6 NA 91.6 Nebraska§§§ 26,313 25,796 (98.0) Census No 96.2 96.7 NA 95.5 Nevada 37,178 1,769 (4.8) Stratified 2-stage cluster sample No 93.0 92.6 NA 92.6 New Hampshire 12,165 11,939 (98.1) Census No ≥92.4 ≥92.4 NA ≥92.4 New Jersey¶¶ 107,630 107,630 (100.0) Census Yes ≥96.1 ≥96.1 ≥96.1 NReq New Mexico 26,896 1,256 (4.7) Stratified 2-stage cluster sample No 94.8 94.9 NA 94.5 New York (including New York City)¶¶ 226,456 226,456 (100.0) Census Yes 97.2 96.9 NA 96.9 New York City¶¶ 100,466 100,466 (100.0) Census No 97.8 97.3 NA 97.4 North Carolina***,§§§ 127,197 120,827 (95.0) Census No 97.0 96.8 NA 96.8 North Dakota 10,365 10,293 (99.3) Census Yes 94.2 94.1 NA 93.9 Ohio 138,753 132,763 (95.7) Census No 92.1 92.1 NA 91.5 Oklahoma*** 53,898 48,481 (89.9) Census (public), voluntary response (private) No 92.6 93.9 96.8 NReq Oregon¶¶,§§§ 45,818 45,818 (100.0) Census Yes 93.2 92.4 94.4 NReq Pennsylvania 141,571 123,377 (87.1) Voluntary response Yes 96.7 97.0 NA 97.0 Rhode Island¶¶,***,§§§ 11,025 11,025 (100.0) Census Yes 96.4 96.2 NA 96.0 South Carolina 58,458 16,174 (27.7) Stratified 1-stage cluster sample No 96.3 96.6 NA 96.1 South Dakota 12,125 12,112 (99.9) Census Yes 96.6 95.9 NA 95.8 Tennessee¶¶,*** 78,743 78,743 (100.0) Census Yes 96.9 96.7 NA 96.8 Texas (including Houston)***,§§§ 387,981 378,008 (97.4) Census Yes 96.9 96.8 NA 96.4 Houston***,§§§ 43,340 38,343 (88.5) Voluntary response (public), Census (private) No 95.1 95.2 NA 94.7 Utah¶¶ 48,827 48,827 (100.0) Census Yes 93.4 93.2 NA 93.7 Vermont¶¶ 6,255 6,255 (100.0) Census Yes 94.1 94.0 NA 93.2 Virginia††† 100,581 4,224 (4.2) Stratified 2-stage cluster sample Yes 95.5 98.2 NA 93.3 Washington*** 85,118 79,977 (94.0) Census Yes 90.6 90.7 NA 89.4 West Virginia**** 19,519 15,120 (77.5) Voluntary response Yes 98.4 98.0 NA 98.1 Wisconsin***,†††,§§§ 66,178 1,223 (1.8) Stratified 2-stage cluster sample No 91.8 96.5 NA 91.2 Wyoming NA NA Not conducted No NA NA NA NA Territories and associated states American Samoa¶¶,**** 758 758 (100.0) Census No 90.9 81.8 NReq NReq Federated States of Micronesia¶¶ 1,886 1,886 (100.0) Census No 94.0 75.8 NReq NReq Guam 2,625 700 (26.7) Stratified 2-stage cluster sample No 85.0 92.0 NReq NReq Marshall Islands¶¶ 1,086 1,086 (100.0) Census No 96.6 67.7 NReq NReq Northern Mariana Islands¶¶ 876 876 (100.0) Census No 92.8 75.6 NA 92.6 Palau¶¶,¶¶¶ 313 313 (100.0) Census No 100.0 100.0 NReq NReq Puerto Rico†††† NA NA Not conducted No NA NA NA NA U.S. Virgin Islands†††† NA NA Not conducted No NA NA NA NA Abbreviations: DTaP/DT = diphtheria and tetanus toxoids (DT) and acellular pertussis vaccine; MMR = measles, mumps, and rubella vaccine; NA = not available; NReq = not required for school entry. * Estimates are adjusted for nonresponse and weighted for sampling where appropriate. Estimates based on a completed vaccine series (i.e., not vaccine-specific) use the “≥” symbol. Coverage might include history of disease or laboratory evidence of immunity. † The kindergarten population is an approximation provided by each program. § Sample designs varied by state or area: census = program attempted to include all schools (public and private) and all children within schools in the assessment and had a student response rate of ≥90%; 1-stage or 2-stage cluster sample = schools were randomly selected, and all children in the selected schools were assessed (1-stage), or a random sample of children within the schools was selected (2-stage); voluntary response = a census with a student response rate of <90% (does not imply that participation was optional). ¶ Some programs publish kindergarten vaccination data online that are more detailed than the state-level estimates in this table. Examples of more detailed data include county, parish, school district, and school-level estimates. ** Most states require 2 doses of MMR; Alaska, New Jersey, and Oregon require 2 doses of measles, 1 dose of mumps, and 1 dose of rubella vaccines. Georgia, New York, New York City, North Carolina, and Virginia require 2 doses of measles and mumps and 1 dose of rubella vaccines. Iowa requires 2 doses of measles and 2 doses of rubella vaccines. †† Pertussis vaccination coverage might include some diphtheria, tetanus toxoids, and pertussis vaccine (DTP) vaccinations if administered in another country or by a vaccination provider who continued to use DTP after 2000. Most states require 5 doses of DTaP for school entry, or 4 doses if the fourth dose was received on or after the fourth birthday; Illinois, Maryland, Virginia, and Wisconsin require 4 doses; Nebraska requires 3 doses. The reported coverage estimates represent the percentage of kindergartners with the state-required number of DTaP doses, except for Kentucky, which requires ≥5 but reports ≥4 doses of DTaP. §§ Medians calculated from data from 49 states and the District of Columbia (i.e., does not include Wyoming, Houston, New York City, American Samoa, Federated States of Micronesia, Guam, Marshall Islands, Northern Mariana Islands, Palau, Puerto Rico, or U.S. Virgin Islands). Coverage data were reported for 3,988,127 kindergartners. ¶¶ The percentage surveyed likely was <100%, but is reported as 100% based on incomplete information about the actual current enrollment. *** Did not include some types of schools, such as online schools or those located on military bases or in correctional facilities. ††† Kindergarten vaccination coverage data were collected from a sample, and exemption data were collected from a census of kindergartners. §§§ Counted some or all vaccine doses received regardless of Advisory Committee on Immunization Practices recommended age and time interval; vaccination coverage rates reported might be higher than those for valid doses. ¶¶¶ For Palau, estimates represent coverage among children in first grade. **** Reported public school data only. †††† Puerto Rico and U.S. Virgin Islands did not report data for the 2017–18 school year because of widespread logistical issues caused by Hurricane Maria. The median percentage of kindergartners with an exemption from one or more required vaccines (not limited to MMR, DTaP, and varicella vaccines) was 2.2% (range = 0.1% [Mississippi] to 7.6% [Oregon]), compared with 2.0% during the 2016–17 school year (Table 2). The median percentage of medical exemptions was 0.2% (range = <0.1% [Hawaii] to 0.8% [Alaska]); the median percentage of nonmedical exemptions was 2.0% (range = <0.1% [California] to 7.5% [Oregon]). Among the 29 states and DC with an increase in exemptions in 2017–18, vaccination coverage was ≥95% in 15 states for MMR, 16 states for DTaP, and 11 states for 2 doses of varicella. TABLE 2 Estimated number and percentage* of children enrolled in kindergarten with reported type of exemption from vaccination, and grace period/provisional enrollment, by immunization program † — United States and territories, 2017–18 school year Immunization program Medical exemptions, no. (%) Nonmedical exemptions Any exemption Grace period or provisional enrollment§ no. (%) Religious no. Philosophical
no. Total
 no. (%) 2017–18, no. 2017–18
% 2016–17 
% Percentage point difference (2016–17 to 2017–18) Median¶ (0.2) — — (2.0) — 2.2 2.0 0.2 (1.8) Alabama 59 (0.1) 460 —** 460 (0.8) 519 0.9 0.7 0.2 None Alaska 75 (0.8) 549 —** 549 (6.1) 624 7.0 6.8 0.2 NR Arizona 400 (0.5) —†† 4,336 4,336 (5.3) 4,736 5.8 5.1 0.7 NR Arkansas 14 (0.1) 213 428 641 (1.6) 655 1.7 1.4 0.3 3,379 (8.5) California 4,190 (0.7) —§§ —§§ 5 (<0.1) 4,195 0.7 1.1 -0.4 10,568 (1.8) Colorado —¶¶ —¶¶ —¶¶ —¶¶ —¶¶ —¶¶ —¶¶ —¶¶ NR Connecticut 126 (0.3) 764 —** 764 (2.0) 890 2.3 2.1 0.2 None Delaware 3 (0.1) 148 —** 148 (1.3) 151 1.4 1.2 0.2 NR District of Columbia 58 (0.7) 352 —** 352 (4.3) 410 5.0 1.1 3.9 NR Florida 1,051 (0.5) 5,394 —** 5,394 (2.4) 6,445 2.9 2.5 0.4 7,349 (3.3) Georgia 102 (0.1) 3,480 —** 3,480 (2.6) 3,582 2.7 2.8 -0.1 287 (0.2) Hawaii 4 (<0.1) 514 —** 514 (3.1) 518 3.1 2.8 0.3 37 (0.2) Idaho 93 (0.4) —§§ —§§ 1,504 (6.7) 1,597 7.1 6.5 0.6 408 (1.8) Illinois —¶¶ —¶¶ —¶¶ —¶¶ —¶¶ —¶¶ —¶¶ —¶¶ NR Indiana 156 (0.2) 579 —** 579 (0.7) 735 0.9 1.0 -0.1 NR Iowa 93 (0.2) 694 —** 694 (1.8) 787 2.0 1.8 0.2 1,356 (3.4) Kansas 125 (0.3) 544 —** 544 (1.4) 669 1.7 1.8 -0.1 NR Kentucky 174 (0.3) 623 —** 623 (1.1) 797 1.4 1.1 0.3 NR Louisiana 61 (0.1) 49 552 601 (1.0) 662 1.1 0.8 0.3 NA Maine 34 (0.3) 58 608 666 (5.0) 700 5.3 5.0 0.3 186 (1.4) Maryland 390 (0.6) 614 —** 614 (0.9) 1,005 1.5 1.4 0.1 NR Massachusetts 166 (0.3) 687 —** 687 (1.1) 853 1.3 1.3 0.0 None Michigan 251 (0.2) 1,095 3,658 4,753 (4.0) 5,004 4.2 3.7 0.5 719 (0.6) Minnesota —¶¶ —¶¶ —¶¶ —¶¶ —¶¶ —¶¶ —¶¶ —¶¶ NR Mississippi 38 (0.1) —†† ** —**,†† 38 0.1 0.1 0.0 165 (0.4) Missouri —¶¶ —¶¶ —¶¶ —¶¶ —¶¶ —¶¶ —¶¶ —¶¶ NR Montana 48 (0.4) 478 —** 478 (3.9) 526 4.3 3.7 0.6 211 (1.7) Nebraska 192 (0.7) 394 —** 394 (1.5) 586 2.2 2.0 0.2 463 (1.8) Nevada 26 (0.1) 1,170 —** 1,170 (3.1) 1,196 3.2 4.4 -1.2 600 (1.6) New Hampshire 22 (0.2) 334 —** 334 (2.7) 357 2.9 3.2 -0.3 573 (4.7) New Jersey 171 (0.2) 2,148 —** 2,148 (2.0) 2,319 2.2 1.9 0.3 991 (0.9) New Mexico 51 (0.2) 394 —** 394 (1.5) 445 1.7 2.3 -0.6 679 (2.5) New York (incl. New York City) 349 (0.2) 2,199 —** 2,199 (1.0) 2,548 1.1 1.0 0.1 4,170 (1.8) New York City 85 (0.1) 581 —** 581 (0.6) 666 0.7 0.6 0.1 1,173 (1.2) North Carolina 284 (0.2) 2,323 —** 2,323 (1.8) 2,607 2.0 1.8 0.2 2,248 (1.8) North Dakota 31 (0.3) 74 244 318 (3.1) 350 3.4 3.4 0.0 NR Ohio 336 (0.2) —§§ —§§ 3,207 (2.3) 3,543 2.6 2.4 0.2 7,367 (5.3) Oklahoma 91 (0.2) 333 657 991 (1.8) 1,182 2.2 1.9 0.3 NR Oregon 62 (0.1) —§§ —§§ 3,427 (7.5) 3,489 7.6 6.7 0.9 NR Pennsylvania 638 (0.5) 1,600 1,779 3,379 (2.4) 4,017 2.8 2.3 0.5 3,124 (2.2) Rhode Island 10 (0.1) 110 —** 110 (1.0) 120 1.1 1.2 -0.1 NR South Carolina 119 (0.2) 1,028 —** 1,028 (1.8) 1,147 2.0 2.0 0.0 328 (0.6) South Dakota 23 (0.2) 238 —** 238 (2.0) 261 2.2 2.0 0.2 NR Tennessee 114 (0.1) 1,085 —** 1,085 (1.4) 1,199 1.5 1.3 0.2 1,124 (1.4) Texas (incl. Houston) 780 (0.2) —§§ —§§ 7,044 (1.8) 7,825 2.0 1.8 0.2 6,811 (1.8) Houston 66 (0.2) —§§ —§§ 459 (1.1) 525 1.2 1.0 0.2 NR Utah 80 (0.2) 19 2,507 2,526 (5.2) 2,606 5.3 5.1 0.2 1,039 (2.1) Vermont 13 (0.2) 227 —** 227 (3.6) 240 3.8 3.9 -0.1 321 (5.1) Virginia 384 (0.4) 1,125 —** 1,125 (1.1) 1,508 1.5 1.2 0.3 NR Washington 621 (0.7) 202 3,142 3,344 (3.9) 3,966 4.7 4.8 -0.1 1,396 (1.6) West Virginia*** 32 (0.2) —†† —** —**,†† 32 0.2 0.3 -0.1 809 (4.1) Wisconsin 164 (0.2) 291 3,122 3,413 (5.2) 3,577 5.4 5.5 -0.1 1,907 (2.9) Wyoming NA NA NA NA NA NA NA NA NA Territories and associated states American Samoa 0 (0.0) 0 —** 0 (0.0) 0 0 0 0 None Federated States of Micronesia 0 (0.0) 0 0 0 (0.0) 0 0 0 0.0 NR Guam 0 (<0.1) 10 —** 10 (0.4) 10 0.4 0.2 0.2 NR Marshall Islands 0 (0.0) —†† —** 0 (0.0) 0 0 0 0.0 NR Northern Mariana Islands 0 (0.0) 0 0 0 (0.0) 0 0 0 0.0 NR Palau††† 0 (0.0) —§§ —§§ 0 (0.0) 0 0 0 0.0 NR Puerto Rico§§§ NA NA NA NA NA NA NA NA NA U.S. Virgin Islands§§§ NA NA NA NA NA NA NA NA NA Abbreviations: NA = not available (i.e., not collected); None = state does not allow grace period or provisional enrollment; NR = not reported to CDC. * Estimates are adjusted for nonresponse and weighted for sampling where appropriate. † Medical exemptions, nonmedical exemptions, and grace period or provisional enrollment status might not be mutually exclusive. Some children might have both medical and nonmedical exemptions, and some enrolled under a grace period or provisional enrollment might be exempt from one or more vaccinations. § A grace period is a set number of days during which a student can be enrolled and attend school without proof of complete vaccination or exemption. Provisional enrollment allows a student without complete vaccination or exemption to attend school while completing a catch-up vaccination schedule. In states with one or both of these policies, the estimates represent the number of kindergartners within a grace period, provisionally enrolled, or some combination of these categories. ¶ Medians calculated from data from 45 states and District of Columbia; states excluded were Colorado, Illinois, Minnesota, Missouri, and Wyoming. Houston, New York City, American Samoa, Federated States of Micronesia, Guam, Marshall Islands, Northern Mariana Islands, Palau, Puerto Rico, and U.S. Virgin Islands also were excluded. Exemption data were reported for 3,634,631 kindergartners. Grace period or provisional enrollment median was calculated from data from 28 states; data were reported for 2,825,691 kindergartners. ** Philosophical exemptions were not allowed. †† Religious exemptions were not allowed. §§ Religious and philosophical exemptions were not reported separately. ¶¶ Program did not report the number of children with exemptions, but instead reported the number of exemptions for each vaccine, which could count some children more than once. Lower bounds of the percentage of children with any exemptions estimated using the individual vaccines with the highest number of exemptions are for Colorado, 0.2% with medical exemptions, 0.3% with religious exemptions, 4.2% with philosophical exemptions, and 4.7% with any exemptions; for Illinois, 0.2% with medical exemptions, 1.4% with religious exemptions, and 1.6% with any exemptions; for Minnesota, 0.2% with medical exemptions, 3.4% with nonmedical exemptions, and 3.5% with any exemptions; and for Missouri, 0.2% with medical exemptions, 2.1% with religious exemptions, and 2.3% with any exemptions. *** Reported public school data only. ††† For Palau, estimates represent exemptions among children in first grade. §§§ Puerto Rico and U.S. Virgin Islands did not report data for the 2017–18 school year because of widespread logistical issues caused by Hurricane Maria. The median reported percentage of kindergartners attending school during a grace period or provisionally enrolled was 1.8% (range = 0.2% [Georgia and Hawaii] to 8.5% [Arkansas]) (Table 2). In 11 of 28 states reporting for the 2017–18 school year, the percentage of children provisionally enrolled or within a grace period at the time of the assessment exceeded the percentage of children with exemptions from ≥1 vaccines. Among the 26 states and DC with MMR coverage <95%, 20 could potentially achieve ≥95% coverage if all nonexempt students who were provisionally enrolled, in a grace period, or otherwise without evidence of complete vaccination were vaccinated (Figure). FIGURE Estimated percentage of kindergartners with documented up-to-date vaccination for measles, mumps, and rubella vaccine (MMR)*; exempt from one or more vaccines † , § ; and not up to date with MMR and not exempt ¶ — selected states and District of Columbia,** 2017–18 school year * Estimates are based on completed vaccine series and are not MMR-specific for Alabama, Florida, Georgia, Iowa, and New Hampshire. Up-to-date coverage reported here is the lower bound of possible MMR coverage. † Most states report the number of kindergartners with an exemption from one or more vaccines. Estimates reported here might include exemptions from vaccines other than MMR, except in Colorado and Minnesota, where MMR-specific exemptions are reported. § Coverage estimates are based on a sample of kindergartners, and exemption estimates are based on a census for Alaska, Kansas, and Wisconsin. ¶ Includes nonexempt students provisionally enrolled, in a grace period, or otherwise without documentation of complete MMR vaccination. ** Figure includes all states with reported MMR coverage for the 2017–18 school year of <95%, the Healthy People 2020 target for MMR vaccination coverage among kindergartners. https://www.healthypeople.gov/. The figure shows the estimated percentage of kindergartners with documented up-to-date vaccination for measles, mumps, and rubella vaccine (MMR); exempt from one or more vaccines; and not up to date with MMR and not exempt in selected states and District of Columbia during the 2017–18 school year. Discussion During the 2017–18 school year, median kindergarten vaccination coverage was close to 95% for MMR, DTaP, and varicella vaccine. The number of states with coverage ≥95% increased from 20 to 23 (MMR), 23 to 25 (DTaP), and 15 to 17 (2 varicella vaccine doses) since the 2016–17 school year ( 2 , 3 ). Coverage increases in selected states might result from modifications to state programs. For example, Pennsylvania reduced its provisional enrollment period from 240 days to 5 days with a medical certificate indicating the scheduling of missing vaccine doses. The Indiana State Department of Health initiated report cards for schools displaying kindergarten vaccination coverage rates and built a bidirectional interface that increased the amount of data in their immunization information system. Kentucky removed the provider signature requirement when printing a certificate of immunization status, allowing school nurses to use the immunization information system certificate to document vaccination history. In Virginia, the number of local health departments participating in back-to-school immunization clinics for children entering school increased, with most local health departments following up with parents about missing vaccinations before the clinics (J Mellerson, CDC, unpublished data, 2018). Although the overall percentage of children with an exemption was low, this was the third consecutive school year that a slight increase was observed ( 2 ). Reasons for the increase cannot be determined from the data reported to CDC but could include the ease of the procedure for obtaining exemptions ( 4 ) or parental vaccine hesitancy ( 5 ). Reported exemptions do not distinguish between exemptions for one vaccine versus all vaccines. Previous studies indicate that most children with exemptions have received at least some vaccines ( 6 – 8 ). Recent data from the National Immunization Survey indicate the percentage of children reaching age 2 years without having received any vaccinations has increased gradually, from 0.9% for children born in 2011 to 1.3% for children born in 2015 ( 9 ). Two of the 10 states with <90% coverage for ≥1 dose of MMR among children aged 19–35 months in the 2014 National Immunization Survey ( 10 ) (the approximate cohort of children entering kindergarten in the 2017–18 school year) also had <90% coverage for ≥2 doses of MMR among kindergartners in 2017–18; in eight states, coverage with ≥2 doses of MMR was <95%, indicating that some children who were undervaccinated in early childhood do not catch up before kindergarten entry. This highlights the importance of school entry vaccination requirements to ensure catch-up vaccination of unvaccinated and undervaccinated children. In 11 of the 28 states reporting 2017–18 grace period or provisional enrollment data, the percentage of kindergartners in these groups at the time of assessment exceeded the percentage with an exemption from one or more vaccines, representing a group of children who could be fully vaccinated with appropriate follow-up. CDC encourages programs to collect and use these data to identify populations of undervaccinated students. Almost all states could achieve ≥95% vaccination coverage if undervaccinated nonexempt children were vaccinated in accordance with local and state vaccination policies. The findings in this report are subject to at least five limitations. First, comparability is limited because of variation in states’ requirements, data collection methods, and definitions of grace period and provisional enrollment. Second, representativeness might be negatively affected because of data collection methodologies that miss some schools or students or assess vaccination status at different times. Third, actual vaccination coverage, exemption rates, or both might be underestimated or overestimated because of inaccurate or absent documentation. Fourth, median coverage estimates include only 49 of 50 states and DC, median exemption estimates include only 45 states and DC, and the median grace period or provisional enrollment estimate includes only 28 states for the 2017–18 school year. Finally, because most states do not report vaccine-specific exemptions, estimates of potentially achievable MMR coverage are approximations. However, if reported exemptions were for a vaccine or vaccines other than MMR, estimates of potentially achievable MMR coverage would be higher than those presented. Kindergarten vaccination requirements help ensure that students are fully vaccinated with age-appropriate vaccines upon school entry. Although overall vaccination coverage is high, coverage could be improved in many states. CDC works with immunization programs to collect and report data on school vaccination coverage, exemption rates, and grace period and provisional enrollment each year. Immunization programs can use these data to understand and address undervaccination among kindergartners and to identify schools and communities where focused interventions could improve coverage with required vaccines. Summary What is already known about this topic? Immunization programs conduct annual kindergarten vaccination assessments to monitor school-entry vaccination coverage for all state-required vaccines. What is added by this report? Median vaccination coverage was 94.3% for 2 doses of measles, mumps, and rubella vaccine; 95.1% for the state-required number of doses of diphtheria and tetanus toxoids and acellular pertussis vaccine; and 93.8% for 2 doses of varicella vaccine. Although the median exemption rate gradually increased for the third year in a row to 2.2%, most undervaccinated children did not have exemptions. What are the implications for public health practice? School assessment allows immunization programs to target interventions to schools with undervaccinated kindergartners to increase compliance with state and local vaccination requirements.