With the latest measles outbreak spreading fast, you may be surprised by the state with the best child vaccination rate in the country. (Gillian Brockell/The Washington Post)

It’s tough being a child in Mississippi. The state has the nation’s worst rates for infant mortality and low-weight newborns. Its childhood poverty rate ranks as the nation’s second worst. Overall, the residents of Mississippi are the unhealthiest in the country.

But there is one notable exception to these dour health stats: Mississippi has the highest vaccination rate for school-age children. It’s not even close. Last year, 99.7 percent of the state’s kindergartners were fully vaccinated. Just 140 students in Mississippi entered school without all of their required shots.

Compare that with California, epicenter of the ongoing Disney measles outbreak, where last year almost 8 percent of kindergartners — totaling 41,000 children — failed to get the required immunizations against mumps, measles and rubella. In Oregon, that number was 6.8 percent. In Pennsylvania, it was nearly 15 percent, or 22,700 kindergartners. And each of these states has suffered measles outbreaks in the last two years.

“It’s nice not having measles in Mississippi,” said Mary Currier, Mississippi state health officer.

The secret of Mississippi’s success stems from a strong public health program and — most importantly — a strict mandatory vaccination law that lacks the loopholes found in almost every other state.

In the Magnolia state, public health trumps parental choice.

In other states, parents have increasingly used exemptions to avoid immunization mandates amid fears that the shots are harmful or unnecessary. Medical authorities have discredited these safety concerns. But a broad scientific consensus on the safety of vaccinations has not slowed exemption demand.

Today, Mississippi and West Virginia are the only states that don’t allow parents to claim religious or philosophical exemptions to the rules for vaccinating children before they enroll in school. Only medical exemptions are allowed in Mississippi and West Virginia, as they are in every state.

But medical exemptions — which might include a child with a weakened immune system — remain rare. They accounted for only 11 percent of exemptions last year, according to the Centers for Disease Control and Prevention.

The rest were religious or philosophical exemptions. Last year, more than 91,600 U.S. kindergartners had one — creating a sizable group of potentially unvaccinated or under-vaccinated children.

The exemptions balancing act

These personal belief exemptions worry public health officials because they poke holes in the disease safety net. Daniel Salmon, associate professor at John Hopkins Bloomberg School of Public Health, co-authored a study that found states offering personal belief exemptions had higher rates of whooping cough — a vaccine-preventable disease. A similar effect was seen in states that made those exemptions easy to obtain.

But, Salmon said, he doesn’t oppose all nonmedical exemptions. The exemptions just needed to be narrow, and parents should be educated about the risks of not vaccinating.

“This is a balancing act,” Salmon said. “There are important policy implications [to allowing parents to make decisions about their children’s health]. But it shouldn’t be easy — the path of least resistance.”

Along with religious exemptions, 19 states also allow parents to claim philosophical exemptions. Together, these personal belief waivers — some requiring nothing more than checking a box of a health form — have surged in popularity. Arkansas and Texas added them in 2003. But four other states recently introduced rules aimed at making them slightly harder to obtain. California last year began requiring a health-care worker to at least sign off.

In the early 1970s, the CDC found that states with school vaccine mandates had about half the measles rate of states without the laws. By 1980, every state had a law on its books. But over the years, more and more states added exemptions.

The lack of a religious exemption in Mississippi — where lawmakers recently passed a bill allowing prayer at some school functions — might be surprising.

The legal fight over exemptions

But attempts to add a religious excuse there have failed. In 1979, the Mississippi Supreme Court wrote a strongly worded defense of the state program, “Is it mandated by the First Amendment to the United States Constitution that innocent children, too young to decide for themselves, are to be denied the protection against crippling and death that immunization provides because of a religious belief adhered to by a parent or parents?”

The push to change the law has heated up in recent years, led by a group called Mississippi Parents for Vaccine Rights. State lawmakers now are considering a bill carving out personal belief exemptions to the state vaccination law. While similar bills in previous years stalled in a state legislature health committee, this year’s initiative is being considered by a state education committee. And public health officials are watching this with alarm.

“We’re hopeful,” said Mary Jo Perry, co-director of the vaccine rights group. “I think what we’re asking is reasonable.”

Perry, who lives outside Jackson, Miss., is not the stereotypical anti-vaccine activist. All three of her children are completely immunized. But her youngest child suffered seizures after a whooping cough vaccine when he was young. She wished she could have delayed or skipped the shot.

In other states, she might have had that right.

“I think Mississippi has been exploited by its reputation for ignorance,” she said.

But Currier, who runs the state health department, said the lack of exemptions is important. Mississippi faces enough health challenges without worrying about measles or whooping cough.

“What we really don’t need is another area we do poorly in and hurt our children,” Currier said.

Still, the state public health officials responded to the pressure to change. In 2009, the state relaxed its requirements for medical exemptions. Parents used to need a doctor to submit paperwork to a county health official, who would evaluate whether the exemption was warranted. Medical exemptions were difficult to obtain. But, Currier said, the state now approves all medical exemptions it receives from doctors. Last year, all 130 requests were approved.

“We saw the need for a pop-off valve” for the building anger about the strict state mandate, Currier said.

Public health officials also are worried about proposals to change the vaccination laws in West Virginia, the only other state without personal belief exemptions.

“Our position is we have some of the best immunization laws in the country,” said Rahul Gupta, West Virginia state health officer.

A favorite chart

To prove the point, West Virginia health officials love to pull out a chart. It’s a Council on Foreign Relations map showing several years of vaccine-preventable disease outbreaks. The outbreaks are listed as colored dots — brown for measles, green for whooping cough and so on.

The face of the United States looks like it’s suffering from a severe case of chicken pox. But the complexions of Mississippi and West Virginia are clear. The colored dots stop at the states’ borders. Gupta pointed out that a measles epidemic last year in Columbus, Ohio, which infected 377 people not far from West Virginia, never made it into the Mountaineer state.

“Immunizations work,” Gupta said. “It’s not rocket science.”