A California bill mandating full vaccination for schoolchildren now awaits an Assembly floor vote after passing the Assembly Health Committee on a 12-6 vote Tuesday.

Senate Bill 277 would end the “personal belief exemption” that allows parents to enroll kids in school without having the full slate of vaccines. It allows for medical exemptions, with a recent amendment seeking to make it easier for physicians to sign off on those opt-outs, though bill opponents insisted the exemptions would remain out of reach for many.

The measure has galvanized constituents like few other bills. Parents from around the state have journeyed to Sacramento to condemn SB 277 at each hearing. They again packed two floors of the Assembly’s spacious Room 4202 on Tuesday, hissing at testimony they disputed and interrupting with derisive laughter when Sen. Richard Pan, D-Sacramento, said his bill was “about freedom” from diseases. One woman was removed after screaming over lawmakers, shouting about seeing her son “on the floor, seizing.”

Shortly before voting, Pan agreed to an amendment allowing doctors to consider family medical history in awarding medical exemptions. Witnesses testified about being fearful of vaccinating their children after an older sibling had an adverse reaction. Another amendment clarified that children who already have personal belief exemptions could keep them until entering kindergarten or seventh grade.

“I do think this bill will leave this committee stronger, as a stronger policy statement now that it does provide extra protection for families,” said Assemblyman Susan Bonilla, D-Concord.

Pan echoed the arguments of other advocates warning of the re-emergence of preventable diseases. He called a measles outbreak at Disneyland evidence that “overuse of the personal belief exemption” has endangered public health, particularly for Californians too young or ill to be vaccinated.

“There are children who have died, there are children who are dying from these diseases, and we don’t want to see them return,” Pan said.

Because no vaccines are 100 percent effective, public health officials call widespread inoculation a bulwark against infection.

“It’s important to have as many in the population immunized as possible,” Dr. Dean Blumberg of the American Academy of Pediatrics testified, “so if an infectious disease does emerge, transmission is limited.”

But opponents questioned the justification for the bill, arguing that California’s overall vaccine rate is sufficiently high to prevent serious outbreaks.

“Our current measles vaccination rate is easily high enough to prevent school spread” of diseases, testified Dr. Jay Gordon, a Santa Monica pediatrician.

Critics distrustful of the medical establishment are unmoved by assurances that vaccines are safe and effective. They relate stories of their “vaccine-injured” children and many see SB 277 as evidence that medical officials and policymakers are in thrall to a profit-obsessed pharmaceutical industry.

“Merck won,” one opponent shouted after the vote.

One Glendale man testified about his son reacting to shots with an increasingly severe cascade of seizures, describing the frightening onset of a condition called severe intractable epilepsy.

“That episode was the last time I heard my son’s voice for three years,” said George Fatheree, adding that he plans to home-school his daughter, currently enrolled in public school with a personal belief exemption, if SB 277 becomes law. “It comes at a tremendous cost to the rights of students to receive education,” he said.

Exchanges became increasingly heated as the hearing stretched into its third hour. A bill supporter, Assemblywoman Lorena Gonzalez, D-San Diego, complained that there is “a bunch of misinformation out there” that is “beyond belief to me.” She sparred with Gordon over whether immigrant children have immunization records.

“How many outbreaks do we need for you to feel there is an issue here?” Assemblyman James Wood, D-Healdsburg, asked opponents.

Before the hearing, hundreds of opponents gathered for a rally on the Capitol steps and cheered raucously for a group of Republican lawmakers urging them on. It was the most public instance yet of legislators joining advocates to speak against the measure.

“This bill, in my opinion, is not vaccines,” Assemblyman Devon Mathis, R-Visalia, told attendees. “It is about combating an overreaching government that is infringing on our constitutional rights.”

Assemblyman Jim Patterson, R-Fresno, invoked “concentration camps” and “internment camps” in suggesting non-vaccinated children would be set apart by not being allowed to attend school. Assemblywoman Shannon Grove, R-Bakersfield, encouraged attendees to broadcast their views, not just at the hearing, but at the ballot box.

“Sacramento politicians, some of them up here, they don’t trust you as parents. They assume you’re ignorant or stupid,” Grove said, “because they’ve forgotten who they work for ... your voter registration will make difference.”