Parents who choose not to immunize their children may cite medical or religious reasons to health authorities. In some states, they hardly need to explain themselves at all. But immunization advocates claim many of these parents are relying on "herd immunity" to protect their kids. Those who are vaccinated, after all, can protect those who are not.
Unless, of course, they don't.
"I think some parents see it as a personal choice, like homeschooling," 36-year-old Jennifer Simon of Oakland, Calif. said. "But when you choose not to vaccinate, you're putting other children at risk. You're relying on others to vaccinate their kids but you're not taking on your social responsibility to protect others. You're putting your child above other people's children."
Earlier this month, Simon and her husband, Dave, took their 6-month-old daughter, Livia, to the doctor. Both Jennifer Simon and her infant were battling runny noses, so she wanted to be a "good parent" and get their child checked out. It was just a common cold but, just two days later, the couple got a call from the doctor's office that made them afraid it could turn into something much worse.
Simon said they were told that a child who had not been vaccinated came into the doctor's office with the measles — and their daughter might have been exposed.
"Then we got a call from the county asking us to quarantine her for 28 days — keep her at home, away from anyone who hasn't had the vaccine and booster," she said.
The current measles outbreak is particularly scary for babies. Like Livia, children in their first year of life cannot get the measles, mumps and rubella vaccine (MMR), meaning the health of their immune systems is dependent on everyone else.
Especially in young children, the measles virus can have some serious consequences — pneumonia, brain damage, hearing loss and even death. In California, where the virus most rampant, 30 babies exposed to measles have been placed under in-home isolation.
The Simons' infant is still symptom-free. And, if all goes well, she'll be removed from quarantine today. Still, it's something her parents say shouldn't have happened.
Some parents who choose not to vaccinate their children may be against orthodox medical interventions. Some may have watched their children experience an adverse episode and linked it to their immunizations.
Others may just be scared. After "The View" co-host Jenny McCarthy's son was diagnosed with autism — and she started speaking out about discredited connections between the syndrome and the nation's fast-paced vaccine schedule — it was concerning.
This anti-vaccine movement, which has been around for years, got a big boost from a 1998 study purporting to show a link between vaccination and autism. The paper was later discredited and retracted, and it's author, Andrew Wakefield, was disciplined. But his message still resonates with the anti-vaccine movement.
All states permit parents to choose not to vaccinate their public school children for legitimate medical reasons, such as anaphylactic allergic response, a life-threatening allergic reaction. All but two states, Mississippi and West Virginia, allow religious exemptions. And 19 states let parents opt-out for philosophical reasons, according to data from the National Conference of State Legislatures.
But some claim the opt-out process in some states is too easy, encouraging the anti-vaccine movement. In New Jersey, for example, parents are required only to sign a note claiming the vaccination would violate their "free exercise of the pupil's religious rights," USA Today reported in a strongly worded editorial titled "Anti-vaccine parents boost measles comeback."
Indeed, a 2012 Emory University study found that nine "easy" states require only a form.
Of 19 states that allow philosophical exemptions, fewer than a third require parents to reapply each year, state their case in writing or obtain a notarized letter from a doctor, Mother Jones reported.
Non-medical vaccine exemptions are risky because they threaten those who cannot be immunized — babies, children too young to finish their boosters, those who have medical reasons such as pregnancy, immune system issues or life-threatening allergies. Those who are not vaccinated can help spread disease during an outbreak.
California public health officials said nearly half of the state's infected residents weren't vaccinated. The state has been in the spotlight since someone infected with the measles virus visited Disneyland in California. Now, the disease has spread to nearly a hundred people among eight states. Although vaccination is no guarantee against disease, research shows one dose of the measles vaccine is 95 percent effective and two doses provide 99 percent protection. And adverse reactions are rare.
Jennifer Simon said she has been concerned, upset and scared over the past month. She and her husband took time off work to stay home with their quarantined baby. Her mother flew in from Texas to help. But, she said, mostly she has been angry that another parent chose not to vaccinate and put her daughter at risk. She said she started posting her story on mommy blogs and social media.
"A Kaiser doctor said it was a child that could have been vaccinated but wasn't. She said they chose not to vaccinate the child," she said. "I go into planning mode when I feel things are out of control, so I think I went to a place where I said, ‘Let's not let this happen to anyone else.'"
And some state lawmakers feel the same way.
Maine has one of the highest exemption rates in the United States, Boston.com reported, citing the Maine Center for Disease Control and Prevention.
Maine state Rep. Ralph Tucker (D) has proposed a bill to remove philosophical exemptions altogether, and fellow Rep. Richard Farnsworth (D) has sponsored legislation to require a doctor's signature for any opt-out request.
"From a public health point of view, we absolutely have to increase our rate of immunizations in order to reduce the risk of transmission for early childhood diseases," Farnsworth told Boston.com. "We've already seen problems with whooping cough, measles, and mumps recently. It's not fair to the general public to have kids who are running around with the potential to expose everybody.
"I would hope we would increase our immunization rate, but my primary concern is to make it so people have to visit a physician before they make this decision."
That's exactly what California did.
Earlier last year, the state enacted a law that requires parents to obtain a doctor's signature on all exemption forms.
But these things take time.
"We went to the doctor to be good parents," Simon said. "Instead, we came out with a potential for measles because someone else chose not to vaccinate and, therefore, expose our child to the disease."