Childhood vaccinations protect kids against a host of diseases, everything from measles to polio to tetanus.
"A lot of the things, threats that parents had to worry about, are gone. Immunization has made that possible," said Dr. Ed Marcuse, Associate Medical Director at Seattle Children's.
But fear of vaccine injuries, and suspected links to autism, have led a number of parents to reject vaccines for their children.
"There's mounting science-based evidence that there is no relationship between autism and vaccines," said Dr. Marcuse.
He said when parents opt their children out of vaccinations it puts whole communities at risk of outbreaks.
"No one wants to immunize anybody against their parent's will. What we want to make sure is that parents have access to good information," he said.
Dr. Marcuse favors new legislation that would add a step when parents opt their child out of required vaccinations for daycare and school.
Today all parents must do to opt out is sign an exemption. The new bill requires a signed form from a health care practitioner showing parents received information about vaccine risks and benefits.
Vashon Island resident March Twisdale, mother of two, objects to the approach.
"I don't love vaccines. They make me nervous on a number of levels. And I have a problem with the whole theory," Twisdale explained.
Both her sons have had whooping cough. She said they're now more immune to getting it again. And she said breast-feeding both of them as infants, and making sure they get plenty of sleep, boosts their immune systems against illness.
Twisdale raises her own chickens and gathers vegetables from her own garden. She said a nutritious organic diet helps her family's immune systems too.
Still, after careful research, she immunized her sons against some diseases, including diphtheria and tetanus. She opted out of other vaccines.
"It is just like so safe to get chickenpox. Are we designed to respond to tetanus? No. From my understanding, usually you die," she said, explaining her thinking on vaccine selection.
Dr. Marcuse doesn't expect a new law to change all parents' minds about vaccines, saying instead, he hopes it will spark discussion.
"Doctors like parents absolutely want to do what's best for a child."
The governor is expected to sign the new bill into law. It would then affect all families enrolling new kids in childcare or school. The law would go into affect 90 days after the governor signed the bill.