The Oregon House passed a bill Monday afternoon that would outlaw all religious and personal belief exemptions for vaccines, potentially forcing major changes on the state with the highest kindergarten vaccine exemption rate in the country amid a record measles outbreak.

The measure, which passed the House 35-25 and now goes to the state Senate for a vote, would prevent children without their required vaccinations from attending school after Aug. 1, 2020, unless they have a doctor-verified medical reason they can’t be immunized.

If passed, nonmedical objections to vaccines would no longer stand in Oregon, a state that medical professionals say exemplifies how easily parents may game the system. According to data gathered by the Oregon Health Authority, about 95% of the 31,500 nonmedical vaccine exemptions submitted in the state last year were done by parents who watched a video and printed out a “do-it-yourself” form.

Vocal objectors to mandatory vaccines often espouse beliefs that vaccines may be linked to autism, though there is no scientific evidence to support those claims. What is clear, the Centers for Disease Control and Prevention says, is that unvaccinated people threaten herd immunity and put sensitive groups at risk, such as young children and immunosuppressed people.

Rep. Sheri Schouten (D), a childhood cancer survivor who was not able to receive vaccines on schedule due to her suppressed immune system, spoke out in support of the bill during Monday’s nearly two-hour, heated hearing.

“I ask all my colleagues to consider children like myself who never had a choice,” she said, “children who can’t safely go to school, children who are unable to participate in community sports and activities, children who are kept from public spaces and families that are kept in constant fear that their child will catch a dangerous and yet preventable disease.”

Oregon could be the fourth state to implement a ban on all nonmedical exemptions if the bill reaches the desk of Gov. Kate Brown (D) and she signs it, as she said she would last month. The bill is largely opposed by state Republicans, though two Democrats also voted against it on Monday.

The bill comes amid one of the worst measles outbreaks in recent history. There have been at least 764 cases in 23 states reported this year, according to the CDC ― marking the biggest outbreak of the virus since vaccination efforts eradicated it nearly 20 years ago.