Photo: Photos By Rich Pedroncelli / Associated Press Photo: Rich Pedroncelli / Associated Press Photo: Rich Pedroncelli / Associated Press

SACRAMENTO — A state senator’s move to scale back a bill giving California officials more say over thousands of medical exemptions for childhood vaccinations did little to dispel opponents’ anger, as hundreds of people packed a Thursday hearing where lawmakers advanced the measure toward passage.

State Sen. Richard Pan, D-Sacramento, amended his SB276 this week to give the state Department of Public Health the power to revoke medical exemptions at schools with large numbers of unvaccinated children — including against measles and rubella — and also exemptions issued by doctors who grant more than five a year.

That won over Gov. Gavin Newsom, who had said he was concerned that Pan’s original proposal — giving the state the power to review all such exemptions — went too far.

It also won over the Assembly Health Committee, which voted 9-2 on Thursday to send the bill toward passage after hearing nearly five hours of emotional testimony from hundreds of people, most of them parents who fear their children could suffer debilitating side-effects from the vaccines. Thousands of protesters filled the halls outside the hearing room and stood outside the Capitol.

“I’m here fighting for our medical freedoms,” said Vanessa Madrid, 34, a mother of two who drove nearly three hours from Salinas to attend the hearing. “We need to wake up and rise up. The government is overreaching.”

After the committee voted, opponents in the room yelled and sobbed. Others sang “Amazing Grace” under the Capitol rotunda.

Pan said SB276 is needed to crack down on unethical doctors issuing exemptions for children in no medical danger from the vaccines. He said concentrations of unvaccinated public school children could be “the tinder for a disease wildfire.”

“This protection is being undermined by a handful of unscrupulous physicians who are profiting from putting children at risk and making our schools less safe,” said Pan, a pediatrician whose 2015 bill eliminated parents’ right to exempt their children for personal reasons.

Photo: Rich Pedroncelli / Associated Press

Medical exemptions for kindergarten students have quadrupled in California since that law took effect. Pan’s bill would give the state Department of Public Health authority to revoke new exemptions, under limited circumstances. It would also allow the public health officials to review and possibly void tens of thousands of existing student exemptions.

SB276 now faces a vote in the full Assembly. The Senate has already approved Pan’s original measure, and would have to vote again on the amended bill if the Assembly approves it.

California requires children attending public schools, including charter schools, to be inoculated against infectious diseases including measles, mumps, chicken pox, tetanus, whooping cough and rubella. If they are not exempted for medical reasons, they must be schooled at home.

Opponents of Pan’s bill lined up hours before the hearing. Some pushed babies in strollers. Others carried signs that labeled Pan a “liar” or likened vaccines to historic atrocities.

Tara Shakeshaft, 44, a math teacher from Oakland, carried her 10-month-old son as she picketed outside the Capitol. She said the child’s primary care physician wouldn’t issue him an exemption to attend day care without immunizations, so she found an “independent” doctor who granted the waiver.

She said the doctor had done a blood test that determined her son could be susceptible to adverse vaccine reactions. Shakeshaft said she agrees with theories that ingredients in vaccines hurt children.

“I have a lot of pressure from society to vaccinate,” she said. “I worry more about how I drive down the highway.”

Pan said California vaccination rates have stalled, a setback after the state made strides to increase immunity following a 2014 measles outbreak that was traced to visitors at Disneyland.

There have been 1,044 confirmed cases of measles in the United States this year — the most since the potentially fatal disease was declared eliminated in 1992. Fifty-three cases have been reported in California.

Assemblyman Jim Wood, D-Healdsburg, the Health Committee chair, said the problem could get much worse than measles outbreaks if the number of exemptions continues to surge. “I fear we’ll go backwards, that we’ll bring polio back to the U.S.,” he said before the vote.

Pan’s original proposal would have required state approval for every request for a medical exemption. Even with his amendments, tens of thousands of existing student exemptions could be subject to state review.

SB276 would require state public health officials to to review new exemptions in two circumstances:

• When a public school has an immunization rate of less than 95%, the threshold for “community immunity” — the level at which enough of a population is protected against a disease to prevent it from spreading.

• When a physician grants more than five exemptions in a calendar year, which supporters of the bill said suggests the doctor could be issuing phony exemptions.

The state could revoke exemptions that it finds are fraudulent or inconsistent with medical guidelines — criteria outlined by the federal Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices or the American Academy of Pediatrics.

Newsom has said he plans to sign the revamped bill if it passes the Legislature with the changes intact. On Tuesday, he told reporters that the new proposal “addresses some of my bureaucratic anxieties.”

Opponents of mandatory childhood vaccines said the amendments do nothing to alleviate their concerns, and they criminalize doctors who know their patients better than bureaucrats do.

Leigh Dundas, an attorney with Advocates for Physicians’ Rights, a group opposed to the bill, said the measure gives the state “unprecedented” power to overturn a doctor’s decision. She said that’s troubling because public health officials would be legally protected from being sued for damages if they incorrectly revoke an exemption.

“It’s not if the state gets it wrong, it’s when the state gets it wrong,” Dundas told lawmakers. “Once we go down this road, it is a slippery slope.”

Under the bill, a parent or guardian would have the right to appeal an exemption denial, and a panel of doctors would review the appeal. The state Health and Human Services secretary would make the final decision.

“Any physician who’s writing appropriate, legitimate medical exemptions has nothing to fear,” Pan said.

Dustin Gardiner is a San Francisco Chronicle staff writer. Email: dustin.gardiner@sfchronicle.com Twitter: @dustingardiner