There is a movement in the U. S. for parents to opt out of having their young children vaccinated.

Twenty states currently allow “personal belief exemptions” when it comes to having a child vaccinated: Arkansas, Arizona, California, Colorado, Idaho, Louisiana, Maine, Michigan, Minnesota, New Mexico, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Texas, Utah, Vermont, Washington and Wisconsin.

 U.S. Centers for Disease Control and Prevention (CDC) recently issued findings that with more kids not being vaccinated, the United States is now experiencing its largest measles outbreak in 15 years. Experts have also blamed a recent resurgence in cases of whooping cough (pertussis), especially in California, on fewer children being vaccinated.

A new study finds that at some schools in California, where parents can opt out of having their children vaccinated, one out of every five kindergarten students is not vaccinated.  This puts those not vaccinated at risk of preventable infectious diseases, as well as other children at the school.

These are schools “where we might be concerned that ‘herd immunity’ has been compromised,” warned lead study author Alison Buttenheim, an assistant professor in family and community health at the University of Pennsylvania School of Nursing.

“Herd immunity is the protection offered to unimmunized people when most people are immunized or otherwise unsusceptible,” she explained. “For example, our herd immunity against measles protects infants, up to age 1, who are too young to receive the MMR [measles, mumps, rubella] shot.”

Dr. Buttenheim added that “schools are an important site of exposure for children. All of our measures point to increasing exposure to intentionally  not vaccinated children among California kindergarteners, a worrisome trend.”

The researchers deemed as “hot spots” schools where more than 20 of 100 children claimed personal belief exemptions.

The researchers found that in 2010, for every 100 children in a California kindergarten, 2.3 had not been vaccinated due to one or more personal belief exemptions. These exempted children tended to cluster in certain schools, typically attending schools where an average of almost 16 of every 100 of their peers also claimed exemptions.

In some schools, more than one in five kindergartners had parental exemptions for not being vaccinated, the study found.

“This looks like an important study, one that’s consistent with what we’ve been learning about philosophical and personal exemptions,” said Dr. Lance Rodewald, director of the immunization services division at the CDC. “Studies done in the past show that the easier it is to get an exemption, the more likely a child will get one. Other studies show that the easier it is to get an exemption, the lower the coverage levels.”

Rodewald said climbing exemption rates can have far-reaching consequences — even for children who get vaccinated.”It does matter for non-exempted children. While with measles vaccination, one dose gives 95 percent protection, the pertussis [whooping cough] vaccine is very good but not perfect. Pertussis wears off over time. [So] even if a child was vaccinated, it’s still possible to get pertussis,” Rodewald explained. “With a lot of exempters, you can attract an outbreak. We’re seeing a lot of pertussis right now.”

Dr. Buttenheim agreed. “Making sure your children are up to date on the recommended immunization schedule is an easy, safe and effective way to protect your child’s health,” she said. “However, no vaccine is 100 percent effective. Your vaccinated child still has a very small — but not zero — probability of contracting a vaccine-preventable disease if exposed.”

Why are parents opting out of having their children vaccinated?

According to Dr. Buttenheim “Parents choose not to have their children vaccinated for many reasons. To generalize across this diverse group, they perceive the risks associated with vaccines to be greater than the risks associated with vaccine-preventable diseases. While there is a very strong scientific consensus that this calculation is not correct, we cannot simply ignore or dismiss parental vaccine hesitancy.

One big fear that many parents have but now has been proven false,  is the fear that having their child vaccinated for measles-mumps-rubella might raise the autism risk for their child. In 1998, a small but widely publicized study appeared to link childhood MMR vaccination to nine cases of autism. The study appeared in the medical journal The Lancet, which retracted the study in 2010. In January of this year, an investigation by another leading British journal, BMJ, denounced the findings as deliberately fraudulent. But the damage was done.”

“In general, parents do value vaccines but exemptions do happen,” said Dr. Rodewald, a pediatrician with the CDC and director of their immunization services division,  “Parents have a lot of questions and they want to make sure that vaccines are effective and safe. It’s important that health professionals like pediatricians, nurse practitioners and school nurses be able to answer questions for parents so they can make informed decisions; decisions of knowledge and strength.”

For a detailed illustration of  Herd Immunity, go to http://www.niaid.nih.gov/topics/pages/communityimmunity.aspx

SOURCES: Alison M. Buttenheim, Ph.D., assistant professor, nursing, department of family and community health, University of Pennsylvania School of Nursing, Philadelphia; Lance Rodewald, M.D., pediatrician and director, immunization services division, National Center for Immunization and Respiratory Diseases, U.S. Centers for Disease Control and Prevention.