SACRAMENTO — A bill to prevent parents from opting their children out of school-required vaccinations could be headed for a major rewrite after lawmakers heard impassioned testimony from hundreds of parents who threatened to take their kids out of school.

The controversial bill stalled in the Senate Education Committee on Wednesday after committee Chairwoman Carol Liu, D-La Cañada Flintridge (Los Angeles County), cautioned bill author Sen. Richard Pan, D-Sacramento, that a vote Wednesday would likely kill the bill.

A one-week delay will give Pan, a pediatrician, time to amend SB277 so that he can get support from committee lawmakers, some of whom echoed the concerns raised by parents. Adding a religious exemption, which 46 other states currently allow, was urged by committee member Sen. Connie M. Leyva, D-Chino (San Bernardino County), but it was unclear whether Pan would incorporate the suggestion.

“Not having a religious exemption is problematic,” Leyva said.

Several lawmakers raised concerns about limiting personal freedom and questioned what’s best for public health. Some lawmakers were concerned that the bill would deprive unvaccinated kids of a constitutionally required education by barring them from schools.

“The trade-off of giving up personal freedoms, even if your child gets sick because of that personal freedom, personal choice, I think that’s a threshold that should be very carefully evaluated before handing it over to a government mandate, and I don’t think we’ve reached that threshold yet,” said Bob Huff, R-Diamond Bar (Los Angeles County), who is on the Education Committee.

Consider amending bill

Pan said later he will think about amending the bill.

“After hearing comments from committee members, we chose to put the vote off until next week to allow a chance to review and consider any changes,” Pan said in a prepared statement issued later in the day. “This is the legislative process at work and if there are changes that will make the bill better, we should take the time to consider them.”

In its current form, SB277 would require children at public and private schools to be vaccinated unless a doctor determines they should be exempt for medical reasons. The bill was a response to a multistate breakout of measles cases that were traced back to an outbreak in December at Disneyland. Many of the children who became ill had not been fully vaccinated.

California allows parents to send their children to school without the required vaccinations if they seek exemptions for personal beliefs, which include religious objections. There were 13,592 personal belief exceptions filed this school year in the state for kindergartners, or 2.5 percent of the total population, according to the California Department of Public Health. Some children are given conditional entry when a vaccine is not due yet, making the total vaccination rate 90.4 percent of the 535,332 students enrolled in kindergartens across the state.

Public health officials say immunization rates need to be at least 90 percent to protect those who can’t receive vaccines because of age or illness.

'Children are at risk’

“Our community immunity is dropping too low and children are at risk,” Pan said.

The halls of the state Capitol were crammed with people who traveled across the state to speak in opposition to the bill.

If the bill passes in a “vote-only” hearing next week, it will head to the Senate Judiciary Committee before going to the full Senate for a vote.

The bill’s co-authors — Pan, and Sen. Ben Allen, a Democrat from Santa Monica who was a school board member — said the bill is needed to protect those who cannot be vaccinated because of medical conditions.

The bill has prompted fiery reactions among some opponents, and Pan received added security in recent days after he received threatening messages on his social media pages and at his office.

A hearing last week in the Senate Health Committee was delayed several times due to opponents’ interruptions, and at least one person was removed from the audience. Wednesday’s hearing moved along more smoothly, and hundreds more people attended to voice their concerns.

“It’s about taking a choice away,” said Leslie Li of San Francisco, who attended the hearing. “I am against vaccinations. I think there are dangerous chemicals in them.”

Many parents opposed to the bill said forcing them to vaccinate their children will leave them no choice but to pull their children out of school.

“I would leave the state” if the bill passes, said Stefanie Jenzeh, an Oakland mother of four. “This is about informed consent. We should be able to make our own decisions.”

Some lawmakers said the way the bill is written, children who are homeschooled would be barred from group learning with other homeschooling families. Allen and Pan said they are willing to work on the language of the bill to ensure that homeschooling families can work together as they often do now.

Other lawmakers questioned whether vaccination rates are already high enough to meet the public interest.

Bill called 'draconian’

“I’m looking for the compelling state interest in doing something this draconian,” said Sen. Loni Hancock, D-Berkeley. “As I read this bill, there is nothing you can do if you chose not to vaccinate your child except personally homeschool them with no one but other family members.”

Carl Krawitt, a father from Corte Madera whose 7-year-old son battled leukemia and could not be vaccinated, said the compelling interest is in ensuring those who can’t be immunized are protected. In the wake of the Disneyland measles outbreak, Krawitt said, he was told that if there was a case at his son’s school, his son would have to stay home for 21 days.

“It was frustrating, infuriating really, to think that Rhett might have to miss more school because of a vaccine-preventable illness because other families were choosing not to immunize,” Krawitt said during testimony in support of the bill. “So, was the idea that our family might have to bear the weight and financial hardship of such a quarantine? My family has already faced the strain that comes along when your kid gets cancer.”

Melody Gutierrez is a San Francisco Chronicle staff writer. E-mail mgutierrez@sfchronicle.com

Twitter: @MelodyGutierrez