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Last year's class of California kindergartners had a record high percentage of parents who used a personal belief exemption to avoid immunization requirements, a development that concerns state health officials.

More than 11,000 kindergartners missed at least one vaccine in 2010 because their parents decided to forgo inoculation. At nearly 2.5 percent of the state's 470,000 kindergartners, that's California's highest rate of declined vaccines since at least 1978, the year before the measles, mumps and rubella vaccine was required.