As the measles outbreak that began in Vancouver, Wash. cracks 60 potential cases and spills over into Portland, Oregon Rep. Mitch Greenlick (D-Portland) is looking to put an end to personal exemptions to vaccine requirements.

His proposed bill, which has not yet been finalized, would eliminate all non-medical exemptions for vaccines the state requires for children attending schools and some childcare facilities. Under existing laws, Oregon residents can opt out of vaccinations for personal, philosophical or religious reasons.

Greenlick says that needs to come to an end so that children are not exposed to unnecessary risks from serious but preventable diseases.

"Those parents that have not vaccinated their kids and exposed them to measles should be ashamed," he says. "We're going to end up with more than 100 cases that have really put those kids in danger. There's no excuse for that. There's no need for that to happen."

The lawmaker's proposal would not force people to vaccinate their children, but it would bar those who choose to forego inoculations from attending schools. Those individuals without required vaccines would likely need to home-school.

"It would make perfect sense for a person to say 'I don't want to vaccinate my kid' if they could believe any other person their kid would meet would be vaccinated," Greenlick says. So-called "herd immunity" can protect the unvaccinated, particularly children who cannot get shots because of allergies or compromised immune systems. "But there's no way we can get to 100 percent [vaccination] without everybody getting in the game."

Greenlick spent his career working in public health, and a full decade as Chair of the Department of Public Health and Preventive Medicine at Oregon Health Sciences University. He says vaccines are one of the most important public health advances of the 20th century and a small number of people who deny the solid science supporting the widespread use of vaccines should not spoil the positive impacts for the rest of the state.

The World Health Organization declared "vaccine hesitancy" one of the top ten threats to public health this year.

"I think it's probably thanks to the internet," Greenlick says. "There's all kinds of junk science that comes off the internet."

According to data published by the National Conference of State Legislatures, only three states—California, Mississippi and West Virginia—do not allow either a religious or personal exemption to required vaccines. Eighteen states allow personal exemptions.

Greenlick says he started getting emails from people who oppose vaccinations even before he publicly announced the legislation in an interview with OPB last week.

"There's a growing number of people who believe vaccinations are harmful rather than the lifesavers they are," he says. "It's roughly the same number of people who believe the earth's flat."

Despite that pushback from a small group of anti-vaxxers, he says he hopes he'll see overwhelming support from his colleagues in the state legislature.