A Bay Area mother formed a Facebook page where parents could arrange play dates for their children with other vaccinated youngsters. Another mom advocates socially isolating the unvaccinated by asking parents if their child is inoculated before accepting a birthday invitation, or even using the swings at the playground. And an Eagle Rock mom says she now asks about vaccine records when she buys used baby clothing.

The fierce debate over childhood vaccines is prompting some parents to take extreme measures to make sure their children are segregated from the unvaccinated.

"If you can’t keep your kids healthy, then what’s the point?" said Heather Peterson, who applied to a new preschool after learning that the second-language French and Spanish immersion school her daughter attends had a worrisome vaccine record.

The current measles outbreak has heightened the concern.

Pasadena mother Ariel Loop took all the precautions she felt necessary to protect her newborn son, getting shots during her pregnancy and keeping him housebound until he was about 2 months old.

Loop and her husband waited until their son Mobius received the vaccine for diphtheria, pertussis and tetanus before finally taking him to Disneyland, she said.

But two weeks after a January visit to the theme park, a red rash appeared on their son.

"There’s just no way," Loop said she thought. "No way."

Mobius’ fever hovered below 102 degrees. Loop, a nurse, gave him Tylenol and a cool bath, but his temperature raged. So they went to the emergency room that afternoon, calling ahead to ensure they could bypass the waiting area.

Days later they received the diagnosis: measles.

The fear of having a child contract a contagious childhood disease has grown in recent years, prompting some parents to rethink choices and activities that once seemed innocuous.

"It’s still scary bringing him out, but there’s only so paranoid you can be," Loop said of her now 5-month-old son. "What am I going to do, not take him to the market?"

Bay Area mother Jocelyn Hybiske helped form a Facebook group called "No Mumps Meet ups," where parents could easily arrange play dates with other vaccinated children.

"You want to feel safe taking your kids out to play," said Hybiske, who has since moved to Seattle and started a similar group there.

Eagle Rock mother Rachel Deutsch said she now asks about vaccination before buying or accepting used baby clothing or gear from other parents and balks at taking her infant son to events where there could be a crowd — though she couldn’t resist taking him recently to a new playground that opened nearby.

"You can’t totally live in a bubble," Deutsch said. "I don’t want to be a paranoid, crazy person."

Deutsch has supported pending state legislation that would restrict vaccine exemptions to medical needs and views tougher laws as a way to keep children out of harm’s way.

Leah Russin, a Palo Alto mother, said she’s also jumped aboard the movement to tighten laws on vaccine exemptions.

"I see this as hand in hand with raising my son," said Russin, who spoke from the perspective of a worried parent at the news conference introducing the proposed legal changes.

Jenna Karvunidis, a mother of three who recently moved to L.A. and writes about feminism and social issues, urged other parents to ask about vaccination rates before paying tuition and agreeing to do even mundane things that might put a child at risk, such as sharing swings, attending parties or holding elevator doors.

It’s unfair, she said, for parents to be pushed into isolation because others refuse or are slow to have their children vaccinated.

"We shouldn’t be skipping birthday parties," she said. "We shouldn’t be afraid to go to school."

Some parents have found refuge at private institutions with stricter vaccine policies such as Toddle Tunes, a music enrichment program for infants and children.

The West Los Angeles business announced last month that only vaccinated children, or those with medical reasons for not being vaccinated, would be permitted in class.

"We feel it’s our duty to protect them as much as we can," said Lisa Mueller, Toddle Tunes owner and chief financial officer.

When the measles outbreak began, some of the youngest students stopped coming to class. But after the policy change, parents of most of their 700 students praised the decision, sent in vaccination records and breathed "huge sighs of relief," Mueller said.

One mother, Beth Wegner, joined dozens of others in expressing thanks on the company’s Facebook page: "Toddle Tunes is now officially the first public place I feel safe bringing my family," she wrote.

Wegner and her husband had delayed some shots during their son’s first year because of health reasons.

After months of keeping him mostly at home and avoiding mommy-and-me groups and even trips to the grocery store, Wegner enrolled him in Toddle Tunes, thankful for a clean space, a strict sick policy and a program that made his face light up with excitement.

There is a "happy medium" between sealing kids in their rooms and endangering them, said David Ziring, a Toddle Tunes parent and associate professor of pediatrics at UCLA’s David Geffen School of Medicine.

Ziring and his wife pulled their daughter out of a preschool after another child contracted whooping cough. They plan to keep her in a private school program where vaccines are required.

And as a pediatric gastroenterologist, Ziring sometimes wears a mask when seeing an unvaccinated patient. The next child he sees could be a transplant patient who may not have been able to stay up to date on vaccines. Plus, his 2-year-old is not yet old enough to be fully immunized.

Every time he walks into a room with an unvaccinated child, Ziring says, his responsibility to protect his daughter comes to mind.

"It’s not necessarily about personal liberty as much as it is about public health."