SALEM — With the nation's highest rate of parents refusing vaccinations for their kindergartners, Oregon has become ground zero for the contentious debate over whether children should be vaccinated.

SALEM — With the nation's highest rate of parents refusing vaccinations for their kindergartners, Oregon has become ground zero for the contentious debate over whether children should be vaccinated.

A growing number of parents are declining some or all vaccines for their children out of fear of harmful side effects, alarming doctors and public health officials who fear the trend will create a resurgence of preventable diseases.

The state Senate is scheduled to vote this week on a bill that would require parents to be educated about vaccines before they can exempt their children from them.

State data released last week show 6.4 percent of Oregon kindergartners this school year had a nonmedical exemption from vaccination for at least one disease, up from 5.8 percent last year.

"This is a public safety disaster waiting to happen," said Sen. Elizabeth Steiner Hayward, a family physician and sponsor of the Senate measure.

The bill would require parents enrolling unvaccinated children in school to prove they consulted a physician for information, or show a certificate verifying they have watched an online educational video about the risks and benefits of immunization. The educational material would be consistent with information provided by the Centers for Disease Control and Prevention.

Opponents say the measure could infringe on religious rights, as well as parents' right to choose what's best for their child.

"The bill as constructed really does eliminate religious freedom," said Sen. Tim Knopp, a bend Republican and an opponent of the bill. "You're forcing someone to go to a doctor, or you're requiring them to get educated about something that they aren't going to do."

Current state law requires all children in public and private schools, preschools and certified child care facilities to be immunized, but parents can seek exemptions for medical or religious reasons.

Parents still would be able to opt out of immunizations under the bill, but Steiner Hayward hopes it will educate them about the risks and inform them about vaccine-preventable diseases and community immunity.

In Oregon, it's easy to decline vaccines for religious reasons: Parents simply sign a form, and their children can go to school without one or more vaccines.

For purposes of the law, the state says a religion can be any system of beliefs, practices or ethical values. And parents don't have to show evidence of their religious or philosophical beliefs to opt out.

Dr. Jay Rosenbloom, a spokesman for Oregonians for Healthy Children, said declining a vaccination doesn't just affect the individual. Oregonians for Healthy Children is led by the Oregon Pediatric Society, which is promoting the bill.

"The more people you have that are unvaccinated, the more likely you are to have those diseases spread," Rosenbloom said.

Although it's difficult to pinpoint the origin of the immunization opt-out trend, Rosenbloom said the percentage of Oregon parents signing personal-beliefs vaccine exemptions has been rising steadily since 2001.

Similar legislation was passed in Washington in 2011. The following school year, the rate of religious immunization exemptions for kindergartners fell by almost 25 percent, according to CDC data.

Rosenbloom noted it's frustrating as a physician to have to compete for credence against actress Jenny McCarthy and other celebrities who have lent their voice to the anti-vaccine movement.

"I don't get the publicity of a Playboy centerfold," he said.

McCarthy is credited with spotlighting the issue after claiming a connection exists between vaccines and autism. Several studies have found no association between vaccines and autism, and the CDC has discredited the idea that autism is linked to immunization.

Jennifer Margulis, an Ashland author and mother of four, said American children are over-vaccinated.

"Why are we giving a vaccine for a sexually transmitted disease at birth?" she said, referring to the required hepatitis B shot.

Margulis selectively vaccinated her children, exempting them from the hepatitis B vaccine. She rejects the notion that parents who refuse immunizations are uninformed.

"People who choose not to vaccinate according to the CDC (recommendations) are really making a thoughtful, careful decision," she said. Still, Margulis said she thinks the legislation is a good idea because parents should be as informed as possible when making such an important decision.

"It's the most educated people who are choosing to do things a little differently," she said.