SACRAMENTO — Democratic-led efforts to ban vaccine exemptions in Oregon and Washington state toppled one after the other last month amid fervent opposition from parents and anti-vaccine groups who say the bills would have trampled their fundamental rights to decide how to care for their own children.

Now it’s California’s turn to try.

On Wednesday, a controversial bill proposed by three state lawmakers to abolish all vaccine exemptions in the Golden State — except for medical reasons — begins an uphill journey through the Legislature. And many observers wonder if it will encounter a similar fate.

Senate Bill 277, co-authored by Sen. Richard Pan, a pediatrician, 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.

The legislation would also require schools to notify parents of immunizations rates at their children’s schools.

The nine-member Senate Health Committee is only the first legislative panel required to vote on the bill. If it passes there, it must make its way in the coming weeks through the Senate education, judiciary and appropriations committees, then wind its way through committees in the state Assembly. Ultimately it must clear both Democratic-controlled chambers and be signed by Democratic Gov. Jerry Brown.

But on this issue, that’s no guarantee the bill will pass, said Bill Whalen, a top aide to former Republican Gov. Pete Wilson and now a fellow at Stanford’s Hoover Institution.

“People think this is about people who are anti-science and not trusting of the government when in fact if you look at a map of California as to where the vaccine rates are the lowest, they’re not in the Central Valley or Orange County, they’re in places like Marin County and Santa Monica,” both Democratic strongholds.

An informal survey of Senate Health Committee members by this newspaper found that three will vote yes, one is “leaning yes,” one will vote no and the other four are undecided.

The debate on the bill comes at a time when the controversial issue that erupted across the country after a December measles outbreak in Disneyland has all but disappeared from the headlines.

In the days leading up to Wednesday’s hearing, the chorus of opponents has been growing louder in the offices of the nine senators on the health committee. They say they are being flooded with emails, letters and calls appealing to them to kill the bill. Among the critics expected in Sacramento this week — Robert F. Kennedy Jr., whose crusade that questions the safety of vaccines helped doom legislative efforts in Oregon.

Pan, a Sacramento Democrat, is cautiously optimistic.

“I have confidence that when my colleagues are presented with the science and the truth about why we need to stop preventable diseases and protect every student’s right to a safe school, SB 277 will pass,” he said.

California is one of 20 states that allow exemptions based on parents’ personal beliefs. In Missouri, the personal belief exemption applies only to day care, preschool and nursery school. Pan convinced his colleagues to pass a law in 2012 that required parents to meet with a medical professional and attest that they had discussed the risks of not vaccinating their child before they could opt out.

But droves of parents are still taking advantage of California’s exemption. 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.

Fifty-seven of the 134 people who contracted measles in California during the recent outbreak were not vaccinated, while another 25 people had had at least one dose of the measles-mumps-rubella vaccine, state health officials reported. Records were unavailable for other vaccinations.

Health experts say such outbreaks endanger people who are either too young or unable to receive vaccines because of a health condition.

As of late March, 178 cases had been reported in the U.S. by the Centers for Disease Control and Prevention since Jan. 1. State health officials say if no new cases are reported by April 17, the outbreak will be considered over.

Critics of Pan’s bill say it’s important to put the outbreak into perspective.

“We ought not let a handful of measles cases at Disneyland turn into a full-scale assault on civil and human rights in America,” Brian Stenzler, president of the California Chiropractic Association, wrote in a letter to senators on the health committee.

Stenzler’s group is one of many opponents, from individual parents to groups like the California-based Million Mamas Movement, lining up against the legislation.

Last month, Stenzler said his members met with 112 of the state’s 120 legislators or their staff to discuss their opposition to SB 277. He emphasized that his group is not anti-vaccine — some members, he said, have vaccinated their children. But, he added, the association does not believe vaccines are 100 percent safe, so “if there is risk, there must be choices.”

His arguments will be bolstered when Kennedy brings his skepticism about vaccines to a Commonwealth Club event Tuesday in San Francisco and then the state Capitol on Wednesday. Kennedy co-wrote a book about the dangers of thimerosal, a mercury-containing preservative in some vaccines, which he alleges was linked to autism, a belief that has been widely discredited by the CDC and multiple scientific studies. But as a precaution, the Food and Drug Administration in 1999 recommended removing thimerosal from vaccines routinely given to infants.

Dorit Reiss, a professor and vaccine law expert at UC San Francisco’s Hastings College of the Law — and a mother who supports the bill — said courts have established the right of a state to compel individuals to receive a vaccination. They have also upheld local government mandates that require vaccinations as a prerequisite for enrolling in school.

And unlike Oregon and Washington, where legislation failed, Reiss believes one major factor is different here:

“California was the place where the measles outbreak started.”

Contact Tracy Seipel at tseipel@mercurynews.com or 408 920-5343 and follow her at Twitter.com/taseipel.