California public health officials say 19 of the 32 cases of measles they have confirmed so far this year are in people who had not been vaccinated, and of that group, 14 were intentionally not vaccinated.

As the number of measles cases continues to grow across the state — there were only three by this time last year — officials at the California Department of Public Health (CDPH) have urged parents against opting out of vaccinating their children. They say an increase in the number of people choosing not to vaccinate could drive a resurgence of the respiratory disease, since the unvaccinated are more susceptible to contracting it.

California allows parents to skip vaccinating their children if they fill out a personal belief exemption form and speak with a doctor about the benefits and risks of vaccines.

CDPH officials say 99 percent of the people who receive two doses of the measles vaccine develop immunity to the disease.

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It was last month that public health officials first identified seven measles patients as having been intentionally not vaccinated. They were between the ages of 7 and 32, said CDPH spokeswoman Kathleen Harriman.

"They were all minors other than two young adults," said Harriman "And the young adults, it was their parents' decision, obviously, not to have them vaccinated when they were children."

CDPH officials could not immediately provide KPCC with the ages of the seven additional people it has determined were intentionally not vaccinated.

The 32 measles cases have been reported in Alameda (1), Contra Costa (4), Los Angeles (10), Orange (6), Riverside (5), San Mateo (1), San Diego (4) and Santa Clara (1) counties. The CDPH has not said where the 14 intentionally unvaccinated people live.

Measles was declared eliminated from the US in 2000, though a handful of new cases arise each year, usually from people who have traveled to countries where measles is common.

Ten of this year's cases involve people who traveled to the Philippines, where there is a large outbreak, or to India or Vietnam, where measles is endemic, health officials say. They have not clarified whether any of those people were vaccinated.