SACRAMENTO — A controversial bill to require vaccinations for all California school children ran into trouble Wednesday, when its author delayed a key Senate committee vote after enraged parents opposed to the legislation demanded lawmakers answer a central question: Don’t all kids — whether they are vaccinated or not — have a right to a public education?

With bill co-author Sen. Richard Pan facing similar questions from fellow committee members, the Sacramento Democrat put the brakes on a scheduled vote in the Senate Education Committee, promising to return with answers in a week for another hearing.

The unexpected retreat seemed a promising turn of events for hundreds of opponents who again showed up in Sacramento to challenge lawmakers and insist the bill would deprive them of their right to choose not to vaccinate their children.

“It shows that legislators realize it’s a bad bill,” said Jean Munoz Keese, a spokeswoman for California Coalition for Health Choice, a group of parents and others who are fighting the bill. “They started looking closely at this bill and realized it is not what Sen. Pan wants people to believe. It essentially will deny children the right to access public education and there are no answers in the current bill to address that.”

Senate Bill 277, which passed its first test a week ago in the Senate Health Committee, needs five votes to proceed out of the Senate Education Committee and then must pass through the Senate Judiciary Committee before heading to the Assembly and then to Gov. Jerry Brown’s desk.

But it was clear the bill would not have had enough votes on Wednesday.

“This is the legislative process at work and if there are changes that will make the bill better, we should take time to consider them,” Pan said in a statement after the hearing.

SB 277 would repeal the state’s personal belief exemption and require that only children who have been immunized for diseases such as measles and whooping cough be admitted to a school in California. It would also require schools to notify parents of immunization rates at their children’s schools. The legislation would make California one of three states that offers only medical exemptions for parents to opt out of vaccinating their children.

It would not apply to any children being home-schooled, and many opponents warned the committee that they will be forced to remove their children from public schools and place their children in home schools if the bill passes.

Yet, many parents have said, schooling their children at home would be unaffordable or impossible for them to do. Even some committee members agreed.

“I have a real concerns about the education piece,” said Sen. Connie Leyva, D-Chino, who recalled that she and her husband were so busy working that they would not have had time nor likely been the best ones to home-school their kids.

“I feel we don’t have a good answer for the education route … that’s a big concern for me as well as not having a religious exemption,” said Leyva. “I feel that is a problem as well.”

Loni Hancock, D-Oakland, and Bob Huff, R-Diamond Bar, also said they could not support the bill.

Hancock said she believed in vaccines but was looking for the “compelling state interest here in doing something as draconian as” force parents who choose not to vaccinate their children to “personally home-school them with nobody but their family members in the home schools.”

For his part, Huff said that he was mostly wrestling with the fact that the bill “would take personal freedoms and subject them to government mandates.”

Even early supporter Marty Block, D-San Diego, wanted to see “a less restrictive education solution” than what the bill proposed.

“I am concerned,” he said, “that we will basically throw kids out of public school and if the person (parent) cannot home-school them, they (still) have a right to an education.”

Bill proponents, such as Redwood City grandmother Liz Ditz, took the delay in stride, saying at least the bill wasn’t voted down.

“I wouldn’t describe it as stalling as much as going back and retrofitting, refining and retooling,” Ditz said.

She too said she had wondered about a question committee chair Carol Liu, D-La Cañada Flintridge, had posed to Pan and co-author Sen. Ben Allen, D-Santa Monica. If passed, the law would take effect on Jan. 1, 2016.

But it wasn’t clear what would happen to children who had not been vaccinated by the deadline. Would they be removed from school?

“That needs to be addressed,” Ditz said.

Barbara O’Connor, director emeritus of the Institute for the Study of Politics and Media at Sacramento State, said the delay is not the death knell of the bill.

“This is the kind of bill that, no matter what happens, it’s good that it’s getting a full airing through these various committees,” she said. In the end, “it may not be on a fast track — it may turn over into a two-year bill.”

The bill was introduced in February in the aftermath of the California measles outbreak in December traced to a case in Disneyland, infecting 134 Californians since and dozens more across the country.

Pan and other health experts believe the rising number of parents taking advantage of California’s personal belief exemption that allows them to forgo their children’s vaccines was a factor in the outbreak. In 2000, fewer than 0.77 percent of California kindergartners had vaccination exemptions. By 2014, the rate had more than tripled to 2.5 percent, or 1 in every 40 children.

Contact Tracy Seipel at 408 920-5343, and follow her at Twitter.com/taseipel.