Despite the fact that whooping cough is reaching epidemic levels in much of the nation, more California parents who send their children to private schools are foregoing some or all vaccines for their kids.
A recent analysis by the Associated Press  shows that the immunization opt-out rate among private schools in the west coast state is more than two times higher than in public schools.
Perhaps even more troubling to public health officials: The rate of children entering private schools without all of their shots jumped by 10 percent last year, while the opt-out figures held steady in public schools for the first time since 2004.
What are the reasons behind the shift?
Many still fear the oft-debated relationship between autism and vaccines, although the prominent study on the supposed link has been debunked and retracted by the medical journal in which it was published.
Other reasons include religious beliefs, and concerns that the shots could have other detrimental health consequences and/or prevent children from developing strong immune systems.
But health officials are concerned that the rise in opt-outs could lead to an increased risk of an outbreak of a communicable disease like whooping cough.
"We're very concerned that those schools are places where disease can spread quite rapidly through the school and into the community, should it get introduced," Dr. Robert Schechter, medical officer with the Immunization Branch of the California Department of Public Health told the AP.
As a result, the state Legislature has approved a bill requiring parents to at least discuss vaccinations with a pediatricians or a school nurse before they can opt-out. Gov. Jerry Brown has until the end of September to sign or veto it.
What do you think about this issue?