California's measles epidemic was no fluke; between 2007 and 2013 the percentage of kindergarteners using a "personal belief" exemption to enroll in school without vaccinations doubled.
In that year, 3 percent of kindergarteners entered school unvaccinated. In some schools, the percentage of vaccinated children was so low that it threatened herd immunity, or the ability for a population to keep a pathogen at bay, according to Stanford health-policy researcher Michelle Mello, PhD, JD.
They found the highest resistance to vaccinations among white, affluent communities. In contrast to previous studies, however, they did not find a correlation between higher levels of education and vaccine exemptions.
"Beliefs about vaccination risk tend to be more entrenched among certain communities of mothers," Mello said. The study didn't investigate reasons for seeking exemption, but other studies suggest some mothers in affluent communities may believe they can adequately protect their children through "intensive parenting techniques" such as an organic diet and restricting contact with sick children, Mello said.
Although California eliminated the personal belief exemption this summer in a broad-reaching law that requires all medically eligible school students to be vaccinated, the study speaks to how other states might approach the problem of vaccine exemptions, Mello said.
Similar clusters of vaccine resistance exist elsewhere and the findings could help public health agencies refine outreach methods, she said. For example, by specifically targeting local groups and reaching out to community leaders, officials may have more success providing education about vaccine risks and benefits, Mello said.
The results are particularly striking given the history of vaccination efforts, she said. In the first half of the twentieth century, public health officials struggled to ensure vaccines reached disadvantaged communities. Now, as fear of the targeted diseases has paled, parents may be more fearful of vaccines, leaving the entire population vulnerable.
Previously: Infectious disease expert discusses concerns about undervaccination and California's measles outbreak, Stanford researchers analyze California's new vaccine law and The earlier the better: Study makes vaccination recommendations for next flu pandemic
Photo by woodleywonderworks