Lauren Gambino / The Associated Press

SALEM — A new law signed by Gov. John Kitzhaber on Wednesday will make it more difficult for parents to enroll unvaccinated children in school.

Parents who decline vaccines for their kids will have to visit a doctor or prove they watched an educational video before sending the children to school or daycare, under the new requirement that goes into effect immediately. Previously, parents could seek nonmedical exceptions by signing a form and citing a religion or system of beliefs.

The law was crafted in response to a growing trend among Oregon parents to refuse some or all vaccines for their children out of fear of harmful side effects.

The state has the nation’s highest rate of kindergartners with nonmedical vaccine exemptions, which alarms doctors and public health officials who fear the trend will create a resurgence of communicable diseases.

Supporters hope the new law will bring the rate down.

“This is a huge step forward for public health in Oregon,” said Sen. Elizabeth Steiner Hayward, a Beaverton Democrat who helped push the bill through. “It’s a triumph of science over fear-mongering.”

Steiner Hayward, a physician, said the requirement will ensure parents have access to accurate information before making an important decision about their children’s health.

Opponents say the measure tramples on the religious rights of minorities who don’t believe in vaccines.

“It’s inappropriate and unconstitutional to force a religious minority to seek a doctor’s permission for something they don’t believe in,” said Sen. Tim Knopp, a Bend Republican. Knopp proposed an alternative measure that would have carved out an exception for parents exempting their children from vaccines for religious reasons.

Kitzhaber, a physician, said, “It is always a good idea for parents to be educated about the impacts their decisions have on children’s health.”