A measles outbreak in southwest Washington has added urgency for Oregon lawmakers as they consider tightening the state’s school vaccination requirements, which are considered some of the most relaxed in the country.

Under the bill, children would have to receive vaccinations in order to attend school, unless they have a doctor’s note seeking an exemption for medical reasons. Parents would no longer be able to claim vaccine exemptions for religious, personal or philosophical reasons. Washington state lawmakers are considering a similar measure this year.

Only three states – California, Mississippi and West Virginia – prohibit nearly all exemptions.