386 - Pre-Kindergarten Access and Exemption Policies Shape Childhood MMR Vaccination in the United States

Publication Number: 2375.386

Eric G. Zhou, Icahn School of Medicine at Mount Sinai, New York, NY, United States; Benjamin Rader, Boston Children's Hospital, Boston, MA, United States

Background: Routine childhood vaccination declined substantially during the COVID-19 pandemic in the United States, yet the policy factors shaping this decline remain poorly understood. Despite kindergarten immunization mandates, vaccination varies significantly across populations and places. Examining coverage before and at school entry is critical for understanding the policy mechanisms driving these differences.

Objective: To assess how state pre-kindergarten (pre-K) program enrollment and vaccine exemption laws jointly relate to MMR uptake among preschool-aged children and to changes in kindergarten MMR coverage from before to after the pandemic.

Design/Methods: We linked child-level MMR vaccination data from the 2023 OutbreaksNearMe (ONM) national survey (n = 22,062) and county-level kindergarten MMR records from 2019–2023 to state prekindergarten (pre-K) enrollment from the National Institute for Early Education Research (NIEER) and state vaccine exemption laws. Analyses tested whether greater pre-K enrollment was associated with higher vaccination coverage and smaller post-pandemic declines, and whether these associations differed between states permitting nonmedical exemptions and those prohibiting them. Models adjusted for parental demographics and community socioeconomic characteristics.

Results: Across both preschool and kindergarten-entry samples, higher state pre-K enrollment was consistently associated with greater MMR coverage (0.7 percentage points per 10-point higher pre-K enrollment; 95% CI, 0.1 to 1.5; and 0.4 points; 95% CI, 0.2 to 0.7, respectively). Among preschool children under 5 years, this association reversed in lenient-exemption states (–1.0 points; 95% CI, –1.8 to –0.4), while states combining universal pre-K access with strict exemption laws showed the highest predicted coverage (0.48 points; 95% CI, 0.07 to 0.89). Kindergarten-entry data showed a 3.6-point average decline in MMR coverage between 2019 and 2023; each 10-point higher pre-K enrollment corresponded to a 0.4-point smaller decline (95% CI, 0.2 to 0.7), an effect nullified in lenient-exemption states (–0.4 points; 95% CI, –0.6 to –0.2).

Conclusion(s): Expanded pre-K access is associated with higher early MMR vaccination and reduced pandemic-related declines at school entry, but these benefits depend on strict exemption policies that prohibit nonmedical opt-outs. Embedding robust immunization requirements within early education systems could strengthen vaccine completion before kindergarten, narrow state-level disparities, and reinforce herd immunity.