Average school-level MMR2 coverage rate experienced by kindergarteners with 0, 1, or 2 doses of measles-containing vaccine, and by school type (random or high-PBE sample). Coverage estimates are provided from observed data in the KRS, and from minimum and maximum coverage imputation scenarios. Imputations are conducted with the missForest procedure. 95% confidence intervals are shown for each estimate. The herd immunity threshold of 88–95% is shown in the horizontal gray bar. MMR2 second dose of measles, mumps, rubella vaccine; KRS 2009 California Department of Public Health Kindergarten Retrospective Survey; Min Imputation and risk estimate under the minimum scenario where exempted children are as vaccinated as the least vaccinated kindergartener at their school; Max Imputation and risk estimate under the maximum scenario where exempted children are as vaccinated as the most vaccinated kindergartener at their school.