Yesterday, Capitol Public Radio in Sacramento ran a piece on the California county with the lowest immunization rates - Nevada County. You can read the piece here. The link also has a video interview with a parent who does not vaccinate her children, and maps with immunization rates by county.
California is among 20 states that allow parents to choose not to immunize because of personal beliefs. In Nevada County, just 73 percent of children entering kindergarten were fully immunized last year. The number fully vaccinated is becoming low enough to threaten herd immunity, and California has been having a pertussis outbreak as a result. While immunization does not confer perfect immunity in all vaccinated children, those who do not receive the vaccine are 23 times as likely to come down with whooping cough (pertussis) as those who are vaccinated.
Some families are unable to receive vaccinations for a variety of reasons (cost, allergies, or other reasons), but in Nevada County, a large fraction of the nonimmunized made a conscious decision not to receive the vaccinations. A total of 17 percent of Nevada County kindergarteners had parents who refused immunization for personal reasons. This figure is much higher than the national rate of 2.5 percent.
These parents are part of the national trend toward skepticism about immunizations. According to the National Immunization Survey, 39% of parents refused or delayed at least one vaccination in 2008, up from 22% in 2003. Among those parents, many were concerned about side effects (including autism, which has been demonstrated in multiple large studies to have no relationship to immunization). In addition, parents who delay or refuse vaccines are much more likely than other parents to believe vaccines are necessary to protect children.
The American Academy of Pediatrics recommends that pediatricians educate parents about the risks their children face from failure to vaccinate, explore reasons for their decision, and revisit the decision at subsequent visits. However, they state that refusal should be respected unless the child is at risk of serious harm, such as during an epidemic; pediatricians should attempt to work with a family if possible rather than referring them to another physician. They also comment,
Parents who refuse immunization on behalf of their children are, in a sense, free riders who take advantage of the benefit created by the participation and assumption of immunization risk or burden by others while refusing to participate in the program themselves. The decision to refuse to immunize a child is made less risky because others have created an environment in which herd immunity will likely keep the unimmunized child safe. These individuals place family interest ahead of civic responsibility.
You can look up the percent of California kindergarteners who were immunized in your local schools in this table (PDF).
The American Academy of Pediatrics statement on parental vaccine refusal is here.