Washington state lawmakers advanced a measure Friday that would remove parents' ability to claim a personal or philosophical exemption to vaccinating their school-age children for measles as the Pacific Northwest struggles with an outbreak of the contagious virus.

The House Health Care and Wellness Committee approved House Bill 1638 on a 10-5 vote. The full House could vote on it in the coming weeks.

The legislation comes amid an outbreak that has sickened more than 50 people in the Pacific Northwest and led Washington Gov. Jay Inslee to declare a state of emergency. Health officials have reported at least 54 known cases in Washington state and four in Oregon.

Washington is among 17 states, including Oregon, that allow some type of non-medical vaccine exemption for "personal, moral or other beliefs," according to the National Conference of State Legislatures.

Washington now allows vaccination exemptions for children at public or private schools or licensed day-care centers based on medical, religious and personal or philosophical beliefs. Unless an exemption is claimed, a child is required to be vaccinated against or show proof of acquired immunity for nearly a dozen diseases — including polio, whooping cough and mumps — before they can attend school or a child care center.

Hundreds of people who oppose ending the exemptions, including environmental activist Robert F. Kennedy Jr., showed up at a public hearing on the legislation last week.

A broader measure introduced in the state Senate, which would not allow personal or philosophical exemptions to be granted for any required school vaccinations, is scheduled for a public hearing next Wednesday.

Four percent of Washington secondary school students have non-medical vaccine exemptions, the state Department of Health said. Of those, 3.7 percent of the exemptions are personal, and the rest are religious.

In Clark County — an area just north of Portland, Oregon, where all but one of the Washington cases are concentrated — 6.7 percent of kindergartners had a non-medical exemption for the 2017-18 school year, health officials said.

California removed personal belief vaccine exemptions for children in both public and private schools in 2015 after a measles outbreak at Disneyland sickened 147 people and spread across the U.S. and into Canada. Vermont also abandoned its personal exemption in 2015.