Maine could end non-medical exemptions for routine childhood vaccines required by schools and certain health care facilities.
The Legislature's Education and Cultural Affairs Committee is set to hold a work session on the bill Wednesday.
Multiple studies have debunked claims that measles, mumps and rubella vaccinations increase the risk for autism. Maine has one of the nation's highest rates of pertussis, also known as whooping cough.
But opponents say argued Maine parents should remain able to opt-out on religious or philosophical grounds.
Meanwhile, a Republican's bill would leave medical exemptions at the "sole discretion" of anyone authorized to administer vaccines.
Federal data shows Maine had among the highest rates of non-medical vaccine exemptions in 2017-2018.
Oregon and Washington are also considering bills to end non-medical exemptions for childhood vaccines.