Of the 15 cases, three are in people who traveled to the Philippines, where a large outbreak is occurring, according to the California Department of Public Health (CDPH). Two more cases are in recently returned travelers from India, where measles is endemic. Nearly half of the cases -- seven -- are in people who were "intentionally not vaccinated," said Dr. Gil Chavez, state epidemiologist with the CDPH.
"Today I am asking unvaccinated Californians who are traveling outside the Americas to get vaccinated before you go," Chavez said.
The measles vaccine is highly effective. It is administered in two doses, as part of the measles-mumps-rubella shot, or MMR. The first dose is given to toddlers at 12-15 months, and the second is recommended before children start kindergarten. CDC guidelines also clearly state that infants who are being taken for travel internationally can receive the first dose as young as 6 months. Two doses provide about 98 percent protection against measles, said Kathleen Harriman, with the CDPH. If you have had the measles, you are also protected.
Measles is one of the most contagious viral illnesses, marked by a fever as high as 105 degrees, cough, runny nose and rash. One-third of cases result in complications ranging from diarrhea, ear infections, pneumonia, seizures and "in some cases death is the final outcome," Chavez said.
And yet, some people continue to worry more about the vaccine than they do about the disease, even though concerns that the MMR vaccine causes illness have not held up scientifically.
"It's very clear to anyone that's been following the issue that there's no information that supports the theory that vaccines are harmful to kids, and that any link to long-term problems, such as autism, has been debunked," Chavez said.
[RELATED: Five Things You Should Know About Vaccines]
Of the seven measles cases in people intentionally not vaccinated, the age range was 1 year to 32 years -- so they are either children or young adults whose parents did not have them vaccinated, Chavez noted.
Harriman said the measles outbreak in the Philippines was exacerbated by Typhoon Haiyan, which hit in November. In 2013, the country saw 1,700 cases and 21 deaths, most in the Manila area, she said.
If you're not vaccinated and "you travel to these areas," Chavez said, "the likelihood of getting infected is very high."
Of the 15 California cases, two are in Contra Costa County, one is in Alameda, and one in San Mateo County. The rest are in Southern California: five in Los Angeles County, three in Riverside County and three in Orange County.