California’s state Assembly approved legislation Tuesday designed to crack down on doctors who sell fraudulent medical exemptions for vaccinations. But Gov. Gavin Newsom’s office said immediately after the vote that he will seek additional amendments affecting one of this legislative session’s most hotly debated issues.

The bill by Democratic Sen. Richard Pan of Sacramento would allow state public health officials to investigate doctors who grant more than five medical exemptions in a year and schools with vaccination rates of less than 95%.

The debate has drawn hundreds of advocates to the state Capitol in emotional support or opposition. A vaccination opponent faces a misdemeanor assault charge after forcefully shoving Pan earlier this month, a confrontation that the activist filmed and shared on social media. Opponents also disrupted a committee hearing Friday even after lawmakers advanced the measure to the full Assembly.

Newsom “appreciates the work the Legislature has done,” his office said in a statement after the Assembly approved the measure on a 47-17 vote. However “there are a few pending technical – but important – changes to the bill that clarify the exemption and appeal process that have broad support.”

Supporters said lower vaccination rates erode the “community immunity” that limits measles outbreaks like those that reached their highest level in decades this year, while opponents said the measure improperly interferes with doctor-patient relationships.

“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 Democratic Assemblywoman Lorena Gonzalez of San Diego, a principal co-author of the bill.

But even some lawmakers who said they support vaccinations objected that the measure goes too far or sets up an expensive, unwieldy bureaucracy.

“We want to promote and support legitimate medical exemptions so that children don’t get hurt,” said Assemblyman Al Muratsuchi, a Democrat from Torrance. “It’s going to have a chilling impact on legitimate medical exemptions and I fear that that would be bad public policy that may lead to some children being injured.”

The Democratic governor, a father of four, earlier expressed his own reservations and negotiated changes with Pan after it initially passed the Senate.

As amended, it would bar doctors from charging fees to fill out medical exemption forms or conducting related medical examinations. They would have to sign the forms under penalty of perjury.

State public health doctors or registered nurses would review exemptions issued by local medical providers who issue five or more a year or at schools with high exemption rates.

The state public health officer, who is a doctor, could revoke any exemptions that don’t meet national guidelines. Parents could appeal to an independent panel of doctors.

Officials could consider families’ medical histories in allowing exemptions in addition to immunization guidelines issued by federal medical authorities.

The debate has received national attention, with actress Jessica Biel joining prominent vaccination critic Robert F. Kennedy Jr. at the Capitol in June to lobby against the bill. Biel later said she supports children being vaccinated but also backs giving families the “right to make educated medical decisions.”