Characteristics Associated With Measles, Mumps, and Rubella Coverage and Exemptions After a School Immunization Law Change in Washington, 2019-2020

BACKGROUND

We aimed to better understand the impact of statewide legislation removing personal belief exemptions (PBEs) for the measles, mumps, and rubella (MMR) school immunization requirement and factors associated with resulting health-seeking behaviors.

METHODS

We used chi-squared tests and logistic regression models to determine individual- and school-level characteristics associated with holding a MMR PBE and with post-law MMR immunization status among students linked to the Washington State Immunization Information System.

RESULTS

Of students with a MMR PBE pre-law change, 43.0% completed the MMR vaccine series and 40.4% sought another exemption type. Religious exemptions made up most new MMR exemptions signed (71.8%), followed by medical exemptions (18.5%), and religious membership exemptions (9.7%). Students were more likely to complete the vaccine series post-law change if they attended a school with a low school-level MMR exemption rate, a public school, or held a lower number of school-required immunization exemptions.

CONCLUSIONS

This study confirms previous concerns that parents might replace their PBE with another exemption type; however, nearly half the students in the cohort completed the MMR vaccine series. Our findings suggest that targeted immunization policies can increase MMR coverage 1-year post-law change but must account for a replacement effect when exemption categories are eliminated.