SACRAMENTO (AP) — A California lawmaker who is proposing to limit the number of schoolchildren who are exempt from being vaccinated said Tuesday that he’s optimistic the bill will advance after a vote was delayed one week.

Sen. Richard Pan, a Democratic pediatrician from Sacramento, said he and Democratic Sen. Ben Allen, a former school board member, have made changes after members of the Senate Education Committee worried it would deprive unvaccinated children from receiving an adequate education.

The amendments allow families that opt out of vaccines to homeschool their children together and let students seek independent study.

“I believe” the amendments “will satisfy many concerns of my colleagues,” Pan said, standing with polio survivors in front of iron lung ventilators, in a video statement. “I’m optimistic that we’re going to get the bill out tomorrow.”

The proposal would eliminate California’s personal belief and religious exemptions so unvaccinated children would not be able to send attend public or private schools. Medical waivers would only be available for children with health problems.

Although the measure has broad support from medical, education and public health groups, opponents have flooded the Capitol to testify at recent hearings and prompted extra security for lawmakers.

The committee is scheduled to vote Wednesday, after one lawmaker was replaced and another was added in recent days.

Democratic leadership removed Republican Minority Leader Bob Huff, an opponent of the bill, and replaced him with Sen. Sharon Runner, R-Lancaster. Runner said she has not decided how she will vote.

The majority party also appointed Sen. Bill Monning, D-Carmel, who had voted for the bill when it was heard in the health committee.

Opponents criticized the moves as outright rigging. “How is that good government?” asked Sylvia Pimentel, a member of the California Coalition for Health Choice, which wants to protect parental rights.

The proposal was among several drafted across the nation in the wake of a measles outbreak that started at Disneyland in December, sickening more than 100 people in the U.S. and Mexico.

The plan faces many legislative hurdles, but if it becomes law, California would join Mississippi and West Virginia as the only states with such strict vaccine rules.

Pan said recent outbreaks of whooping cough and measles serve as a reminder of California’s need to maintain high vaccination rates, particularly in schools where some children cannot be immunized due to medical conditions.

“We need to protect our children, not only our own but other children in the community as well,” Pan said.

Many opposing parents, however, argue SB277 will not protect children with weak immune systems. They say vaccines have been linked to autism and other developmental diseases, even as the medical community says such claims have been disproved.