News that California has already had 15 cases of measles this year has public health officials on alert, particularly because of the growing number of parents opting not to vaccinate their children. Last year at this time there were only two cases.
Health officials have determined that at least seven of the 15 measles victims were intentionally not vaccinated. That has stoked their concern that if more people choose not to vaccinate, it could lead to a more widespread outbreak of measles or other communicable diseases.
In California, parents who do not want to vaccinate their children can opt out with a Personal Belief Exemption. In Los Angeles County the rate of personal belief exemptions is low, at 1.8 percent, said Robert Kim-Farley, director of the L.A. County Department of Public Health's division of communicable disease control and prevention.
But the rate is rising, albeit slowly. Prior to 2007, it was below 1 percent.
A new law went into effect this year intended to encourage more families to reconsider. Before a parent can opt out, she must visit a doctor to talk about the benefits and risks of vaccines, and the doctor must sign the Personal Belief Exemption form.
Public health officials say the number of people refusing to vaccinate their children is still small enough not to pose a threat of a large-scale outbreak. But they note that the larger that number gets, the more impact it has on what they call herd immunity. With herd immunity, a large enough portion of a community is vaccinated to protect the unvaccinated from an infectious disease, according to the Centers for Disease Control and Prevention (CDC).
In California, about 97 percent of children have had both doses of the measles vaccine by kindergarten, said Kathleen Harriman, a section chief at the state health department’s immunization section.
Despite what officials consider generally good coverage, they do see clusters of non-vaccinated children in certain areas, including Marin County, Santa Cruz, Malibu and at certain private schools.
Nationally, children are supposed to get two doses of measles vaccine before they enter kindergarten. About 91 percent of kids have received at least one dose of the vaccine by the time they are 3 years old, said Harriman.
It was thought that measles had been eradicated in 2000, but it resurfaced in subsequent years. In California, there have been from four to 40 cases a year since, said state epidemiologist Gil Chavez.
Measles is an acute viral infection characterized by fever, cough, runny nose, eye redness and skin rash. About one third of cases develop serious complications, including pneumonia and encephalitis, and it kills one to three out of every 1,000 children who contract it, according to Paul Krogstad, professor of pediatric infectious disease at Mattel Children’s Hospital UCLA.
California's last measles outbreak occurred in 2008 and was concentrated in San Diego. The original carrier was a child who brought the disease back from Switzerland after a family vacation. The child was from a family that chose not to vaccinate. San Diego health officials determined that more than 800 people were exposed; they took steps to prevent its spread, and in the end only a dozen children came down with measles.
Measles is just the latest virus to raise alarms. The flu has claimed more lives this season than in any since the epidemic of 2009-10. Pertussis, or whooping cough, has also surged, claiming the life of an infant in Riverside County last month. Researchers say vaccine refusal did play a role in the 2010 pertussis outbreak in California that claimed 10 lives.
Families that opt out of vaccination for non-religious reasons are often skeptical about the safety of the ingredients in vaccines and their efficacy. Some also choose to delay vaccinating their children in the belief that kids are required to get too many shots before kindergarten.
"These are not life-threatening things; they are normal childhood illnesses," said Terry Roark, who said she joined the anti-vaccination movement after her child was injured by the DPT vaccine in the 1970s. "A healthy child contracting a childhood illness is not going to die from it."
Many of those who choose not to vaccinate their children are convinced that vaccines cause autism. The CDC says research has not found such a link.
The most high-profile research linking vaccines to autism was a 1998 study published in the medical journal The Lancet. After an investigation, Britain's General Medical Council found the study's author, Andrew Wakefield, guilty of serious professional misconduct in his research and banned him from practicing medicine there. The Lancet subsequently retracted the article. A 2011 article in the British Medical Journal declared that Wakefield had doctored his findings.
But the debunking of the Wakefield study has not slowed down the anti-vaccination movement, which frustrates health experts.
"It’s clear to anyone that has been following the issue that there is absolutely no information that supports the theory that vaccinations are harmful to kids," said state epidemiologist Chavez. "The illnesses that used to be the thing of the past continue to make a comeback because we have people who choose not to be vaccinated."
While there are still a relative handful of measles cases in California each year, there were about 39,000 a year before the measles vaccines was introduced in the 1960s.
"We in public health are always concerned about philosophies or behaviors that put the community at risk," said Kim-Farley. "Especially given the fact that we are in such a global society, sometimes in countries where measles is circulating."
Travel to the Philippines is especially worrisome because of a recent measles outbreak there that has resulted in several deaths, said the state health department's Harriman.
Of the 15 cases reported in California three of the individuals had traveled to the Philippines and two had been to India, where measles is prevalent. One was an infant too young for the vaccine. Only two were fully vaccinated and could prove it, Harriman said.
Five of the measles cases were in Los Angeles County, three were in Riverside County, three were in Orange County, and four were in the Bay Area.