A legislative committee is expected to vote Friday on a bill that would make it more difficult for parents to opt out of the vaccinations required to attend public school in Maine.

The measure, which drew scores of supporters and opponents to a State House hearing last week, will likely win a recommendation from the Health and Human Services Committee. However, it faces an uncertain future because of opposition from Gov. Paul LePage, and proponents may not be able to muster enough support on the floor of the Legislature for the two-thirds margin needed to overturn a veto.

The bill by Rep. Linda Sanborn, D-Gorham, would require parents seeking a philosophic exemption from vaccines to consult with a medical professional and obtain a signature before opting out. Maine has one of the highest rates in the United States of voluntary opt-outs for children entering kindergarten – 5.2 percent in 2013-14 and 3.9 percent in 2014-15. In at least 60 schools, voluntary opt-out rates exceed 10 percent.

While Maine allows parents to obtain non-medical exemptions on philosophic and religious grounds, almost all of the opt-outs in Maine are for philosophic reasons, according to the Maine Center for Disease Control data.

Rep. Richard Malaby, R-Hancock, said he’s against Sanborn’s bill, L.D. 471, and in favor of parental choice, although he had his own children vaccinated.

“I’m all for informed consent, but I don’t think it’s an appropriate role for the state to script this conversation,” Malaby said.

Dr. Dora Anne Mills, a former Maine CDC director and the vice president of clinical affairs at the University of New England, compared vaccines to the debate over second-hand smoke. It took several sessions before lawmakers agreed to ban smoking in indoor public places in separate laws approved in the mid- to late-2000s. While Mills said there always will be a minority who are skeptical of vaccine safety, or who falsely believe debunked claims that vaccines cause autism, general awareness that unvaccinated students pose a public health risk will help the bill become law, if not this year than in the near future.

“The culture has to change, where it’s no longer socially acceptable to send an unvaccinated child to school,” Mills said.

Scientific research overwhelmingly supports that vaccines work, and that immunization rates need to be as high as possible to reach “herd immunity,” which protects those who are not old enough to be vaccinated or those who are immune-compromised from an illness, such as leukemia. Herd immunity starts waning for some diseases when less than 95 percent of the population is vaccinated.

Several states have tightened vaccination requirements in recent years, and a measles outbreak that originated at Disneyland in California this winter put a spotlight on areas with low childhood vaccination rates.

California and Vermont are poised to eliminate philosophic exemptions, with governors in both states indicating they would sign bills making their way through state legislatures. In Vermont, Democratic Vermont Gov. Peter Shumlin reversed his stance from 2012, when he vetoed a similar bill.