IN WASHINGTON state this spring, a woman died of measles — the first confirmed death of the disease in the United States since 2003. And in April, Massachusetts had its first case of measles this year (a second one was a misdiagnosis ). While an outbreak of the once-rare disease here is unlikely, thanks to relatively high rates of student immunization in Massachusetts schools , legislators are considering a misguided bill that would allow more parents to refuse vaccinations for their children by adding a “personal beliefs” exemption to the state law requiring all children to be vaccinated before they can be admitted to school. Currently, parents can only cite a religious belief or a medical reason to avoid vaccines. But even with the current limited exemptions, some schools have exemption rates over 10 percent, as the graphic below shows. That’s why expanding exemptions would be a step backward in preventing a major outbreak. Indeed, the rise in vaccine rejection — that rare phenomenon where the right meets the left — is a public health issue. Allowing personal beliefs to inform parents’ immunizations decisions creates a slippery slope that will only endanger whole communities. That’s why states like California are headed in the opposite direction, narrowing vaccine exemptions. The more people who are immunized, the more effective the vaccines. The Massachusetts proposal , filed by state Senator Joan Lovely, should be rejected.