In the new California study, researchers analyzed state health department figures on personal belief exemptions among kindergartners. Some schools had much larger proportions of these children than others, raising concerns that clusters of unvaccinated children might lead to outbreaks of diseases like measles, mumps and rubella.
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 bypassed immunization 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 vaccination, the study found. More than 7,000 kindergarteners across California attended these schools, including 2,700 who were exempted.
"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 o
All rights reserved