California lawmakers are hearing impassioned pleas from parents and doctors during their first hearing on a bill that would require schoolchildren to be vaccinated.

The Senate Health Committee on Wednesday is considering SB277 by Sen. Richard Pan, Democratic pediatrician from Sacramento.

Under the proposal, parents could no longer cite personal beliefs or religious reasons to send unvaccinated children to private and public schools unless a child's health is in danger.

Ariel Loop told lawmakers she shouldn't have had to fear for her infant son's life after he contracted measles at Disneyland.

But Karen Kain, whose daughter died as a result of injuries from a vaccine, pleaded for maintaining parental rights.

If passed, California would join Mississippi and West Virginia as the only other states with such strict vaccine rules.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

A bill requiring California schoolchildren to be vaccinated will receive its first public hearing Wednesday after similar efforts to limit exemptions in Washington and Oregon failed to advance.

The California Senate health committee will hear SB277 by Sen. Richard Pan, a Democratic pediatrician from Sacramento. Under the proposal by Pan and Democratic Sen. Ben Allen, a former Santa Monica school board member, parents could no longer cite personal beliefs or religious reasons to send unvaccinated children to private and public schools unless a child's health is in danger.

If passed, California would join Mississippi and West Virginia as the only other states with such strict vaccine rules.

Similar efforts to tighten rules for vaccine exemptions were proposed in other states after a measles outbreak in December that started at Disneyland and sickened more than 100 people across the U.S. and in Mexico. But the proposals have become an emotionally charged topic.

Opponents include Robert Kennedy Jr., the nephew of President John F. Kennedy and son of former U.S. Attorney General Robert Kennedy, who said at a Capitol rally head of Wednesday's legislative hearing that he supports using vaccines and had all six of his children vaccinated, but believes the pharmaceutical industry profits immensely when governments make vaccines mandatory.

"The checks and balances in our democratic system that are supposed stand between corporate power and our little children have been removed," Kennedy said. "And there's only one barrier left and that's the parents."

According to the National Conference of State Legislatures, California is among 20 states that allow for personal belief exemptions and 48 that allow for religious exemptions.

The push to limit exemptions was dealt two recent blows when bills in Oregon and Washington failed. Oregon's measure would have restricted vaccine exemptions for only medical reasons while Washington would have removed the personal belief allowance for an exemption.

Public health officials believe an immunization rate of at least 90 percent is critical to minimizing the potential for a disease outbreak. California's kindergarteners met that threshold at the start of this school year, according to state statistics: 2 percent were exempted because of their parents' personal beliefs and another half a percent were exempted because of their parents' religion.

Less than one-fifth of a percent of all California students — about 1,000 — had a medical vaccine exemption that would be preserved under the bill.