Tom Wilemon

twilemon@tennessean.com

An outbreak of measles in California this year has sickened 51.

48 states have opt-out laws for required school vaccines.

Politics of Childhood Vaccines discussion will be in Room 208 of Light Hall, Vanderbilt University.

It is 4-5:30 p.m. Wednesday and is free and open to the public.

With preventable diseases such as measles staging a resurgence, a leading Nashville physician says it's time for Tennessee and other states to stop allowing parents to opt out of vaccinating their children.

Exemptions for personal or religious beliefs put children at risk who have legitimate medical reasons for not getting vaccines, said Dr. Bill Schaffner, an infectious diseases professor at Vanderbilt University.

Forty-eight states, including Tennessee, have passed laws allowing parents to opt out of mandatory school vaccinations. About 2 percent of Tennessee children do not receive their required shots because parents cite religious or medical reasons, according to the state health department.

Infectious disease experts worry about that percentage rising, as it has in states such as California, where the rate of parents citing personal belief exemptions rose 50 percent in three years.

California has reported 51 cases of measles in 2014, compared to four cases at this point last year. In the state of Washington, public health officials last week were retracing the steps of a woman in her 20s with measles who attended a tightly packed Kings of Leon concert. So far this year, no illnesses have been reported in Tennessee, but three cases did occur in 2011.

Outbreaks of other infectious diseases, most notably whooping cough, have been occurring across the country, as well.

"We have to be much more active — not only in providing more information, but also in trying to close some of the loopholes in the state immunization laws that permit parents to opt out of vaccinations when they send their children to day care, kindergarten and to school," Schaffner said.

He is on a panel discussing "The Politics of Childhood Vaccines" Wednesday at Vanderbilt. Professor Anna Kirkland of the University of Michigan, the featured speaker, is writing a book called "Vaccine Trials" that details how the federal government ensures and monitors vaccine safety.

"The pediatricians are just really having a really difficult time day after day trying to talk to people about this in their offices," Kirkland said.

Many in medicine mistakenly thought the anti-vaccine movement would be a passing fad, Schaffner said. The movement took off after a British medical journal published a study in 1998 linking the measles vaccine to autism — a study that has since been discredited and retracted.

• Related:Vanderbilt study uncovers clues to autism

But the opposition to vaccines persists.

Any action to remove exemptions for mandated school vaccinations in Tennessee would face certain opposition from organizations such as Vaccination Liberation. Kelly Riggs, a spokeswoman for the organization in Knoxville, said the opt-out law in Tennessee should be expanded, not restricted. She wants the state to add philosophical objections to the religious and medical reasons for refusing mandated vaccinations to attend public schools.

"We don't want the state or any government to tell us what we need to do with our child or body," Riggs said.

Besides vaccines, parents are also increasingly refusing vitamin K shots for newborns. The vitamin prevents a bleeding disorder in babies so rare that it typically affects fewer then one in 10,000 newborns. But doctors at Monroe Carell Jr. Children's Hospital at Vanderbilt diagnosed four cases between February and September of last year.

An investigation by the Tennessee Department of Health found that 3.4 percent of 3,080 infants discharged from one Nashville hospital didn't receive a vitamin K injection. Twenty-eight percent of 218 babies born with the assistance of birthing centers didn't get it.

Reach Tom Wilemon at 615-726-5961 and on Twitter @TomWilemon.