Most of the measles cases originated at two Disney theme parks in Anaheim, California, where the state’s public health department said on Wednesday that the majority of the people who caught it were unvaccinated. State epidemiologists think the outbreak began with a measles-infected visitor in mid- to late December, and urged people who haven’t been vaccinated to avoid theme parks, airports and other places where international travelers might visit.
The measles outbreak sheds light on a growing anti-vaccination movement, spread by parents and advocates, including former ABC television host Jenny McCarthy. As a result, parents may opt not to immunize their children because of religious beliefs or the fear that vaccines are linked to developmental problems such as autism. While every U.S. state requires children to provide proof of immunization before entering public school, most states offer parents religious exemptions from vaccinating their kids before enrollment, and 18 states allow them to skip out on vaccines due to “personal beliefs,” according to the Johns Hopkins Institute for Vaccine Safety.
Scientists have thoroughly debunked the notion that autism is linked to vaccines, but certain U.S. states such as California, Oregon, Washington and Vermont have seen a rise in vaccine refusals from parents. A 2009 study in the New England Journal of Medicine found that state-level vaccine exemptions based on personal beliefs increased to an average of 2.54 percent in 2004 from 0.99 percent in 1991. More recent data show that “personal beliefs” exemptions among kindergartners have risen by nearly 1 percentage point since 2008 (PDF) in California, and a study published Monday in the journal Pediatrics identified a number of unvaccinated “hot spots” in California’s Bay Area, some where more than 10 percent of parents don’t vaccinate their kids.