Amid the measles outbreak that was traced to Disneyland visitors nearly a year ago, criticism was directed at California parents who got vaccine exemptions for their children based on "personal beliefs," or non-medical reasons.

A new study finds a bit of good news: a fair number of exempted children in the state actually may be vaccinated.

The lead author of the study, published in the journal Vaccine, was Alison M. Buttenheim, an assistant professor at the University of Pennsylvania School of Nursing.

The study looked at kindergarteners from 2009, a year when California collected additional data on children whose parents sought exemptions.

In a separate blog post, Buttenheim listed reasons that some of these exempted children may actually be vaccinated.  Among them:  parents may have requested exemptions simply because they were unable to locate their children's vaccination records.

Along with the good news comes a note of caution, the authors wrote.

Previous studies have calculated the risk of getting measles for unvaccinated children, but those studies relied on data from exemption rates, not actual vaccination.

Since some of those children are, in fact, vaccinated, that suggests the true risk of not being vaccinated is even higher.


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