When a 2015 measles outbreak in California left hundreds of people infected, public health experts in South Carolina lauded the Palmetto State's relatively strict vaccination regulations.
That outbreak, traced to Disneyland, spread so widely because vaccination rates among people exposed to the measles might have been as low as 50 percent, researchers concluded in a study published in JAMA Pediatrics. Herd immunity, a term used to describe the protection afforded to a community when most people have been vaccinated, doesn't work when vaccination rates are that low.
Vaccination rates run much higher in South Carolina because the state Department of Health and Environmental doesn't allow parents to claim "personal exemptions" for their children to skirt school vaccine rules.
The only way children are allowed to attend public school in South Carolina if they haven't been vaccinated is if they qualify for a medical exemption — meaning they need a doctor’s note — or a religious exemption.
The religious exemptions are easier to come by. Parents only need to fill out a form from their local health department and have it notarized. They're not actually required to answer questions about their religious beliefs.
That may present a problem as the anti-vaccine movement gains momentum. President Donald Trump has repeatedly endorsed a debunked theory that vaccines cause autism and, in January, appointed Robert F. Kennedy Jr. as chairman of a committee to study vaccine safety. Kennedy, like Trump, has questioned the safety of vaccines.
Meanwhile, in South Carolina, DHEC data indicates the number of religious exemptions on file increased nearly 70 percent between 2013 and 2017, from 4,761 exemptions on record during the 2013-2014 school year to 8,074 exemptions during 2016-2017.
The number of religious exemptions increased most dramatically in the Upstate, by 76 percent, from 2,044 on record in 2013-2014 to 3,611 in 2016-2017.
By comparison, during the most recent year records are available, DHEC reported 1,464 religious exemptions were filed in the Lowcountry; 2,260 in the Midlands; and 734 in the Pee Dee. The number of exemptions in each region climbed by at least 50 percent since 2013.
"The slightly increasing rates of religious exemptions, particularly in certain parts of the state, are concerning to DHEC because it puts people at increased risk for the spread of vaccine preventable diseases," DHEC spokeswoman Adrianna Bradley wrote in an email.
Bradley noted the number of religious exemptions is still relatively small. DHEC numbers show only 1.02 percent of the total population had a religious exemption during the 2016-2017 school year.
"Outbreaks of vaccine preventable diseases in communities with low vaccination rates due to religious exemptions are well documented," Bradley said. "DHEC maintains the ability to exclude students who are not vaccinated when there is a case of a vaccine preventable disease in a school."
Dr. Henry Lemon, a pediatrician at the Medical University of South Carolina, said he doesn't see many vaccine skeptics at his practice in North Charleston. But he suspected some parents may be requesting these religious exemptions through DHEC because "it's the path of least resistance."
Research shows that pediatricians must tread lightly with parents who believe vaccinations may be harmful, he said. Doctors who try to convince them otherwise run the risk of further alienating families.
"The idea is they cling more tightly to their beliefs when they are challenged," Lemon said.
Doctors are advised to listen to the parents' concerns but not to coerce them into action, he said.
"They don’t feel like these diseases are common enough or severe enough and they start to believe there’s more harm than good (in the vaccine)," Lemon said.
Children are very vulnerable to some of these diseases. Until they turn 2 years old, babies and toddlers don't have a fully developed immune system, he said, and vaccines are "designed to protect against very aggressive bacteria."