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Unvaccinated People Make Up Large Portion Of Measles Cases In California

Graphic shows where measles outbreaks occurred in California in 2014.
Capital Public Radio
Graphic shows where measles outbreaks occurred in California in 2014.

California health officials say almost half of the 32 Californians known to have contracted measles are in families that chose not to vaccinate.

Some of the measles cases are linked to international travel. UC Davis infectious disease expert Dr. Dean Blumberg says measles wouldn’t exist in California without that external exposure. But as more people choose not to get vaccinated, vulnerability increases.

“The more people who opt out of immunization, that leaves a larger susceptible pool, and then leads to increased transmission, and then that really is not only a danger to those who are not vaccinated, but also a danger to those who are vaccinated.”


People most likely to get measles are either too young to be vaccinated, or part of a small percentage of people for whom the vaccine is ineffective.

Measles has been identified in eight California counties so far, mostly located on the coast. Fourteen of the measles cases reported this year are among unvaccinated adults or kids whose parents received a personal belief exemption.

“Absolutely, I think too many people are option out,” Blumberg says.

But he says the larger the pool of unprotected people, the greater the danger even to people who are vaccinated.

“We’re going to constantly be having this challenge of exposure. And the issue is, the more people who are susceptible to these vaccine preventable diseases, the more likely there is to be continuing transmission.”


Blumberg runs a clinic to help families comply with a new law that requires parents to consult a physician before opting out of the vaccines for their children.