Score one for the anti-vaccine parents: The federal government recently concluded, in response to a claim, that vaccines may have triggered one young girl's autism. Score many more for the doctors: Study after study has shown inoculation to be an infinitesimal part of a vast and complex syndrome. Yet the number of California parents seeking exemptions from vaccination, based on their personal beliefs, is rising and in various counties ranges from 5% to 15% -- high enough to endanger vaccinated children as well. This month, Los Angeles County reported its first measles case in two years -- an unvaccinated toddler. What we don't want is a return to 1989-91, when complacency about vaccines led to more than 6,000 cases in the county.
A small but vocal group of parents clings to the belief that vaccines cause autism. They particularly target thimerosal, a vaccine preservative containing ethyl mercury. Perhaps the strongest evidence against the thimerosal theory is that after the preservative was taken out of vaccines a few years ago, autism rates stayed steady or perhaps even increased.
The case of Hannah Poling refueled the anti-vaccine argument. In March, the 9-year-old's parents won a concession from the government in their claim that inoculations triggered Hannah's autism. But Hannah has a cell-metabolism disorder and, because she was late on her vaccinations, had several at once. Her story might fit with research findings that certain genetic mutations predispose some children toward autism, which might then be set off by something in the environment. In rare cases, doctors think, that "something" might be a vaccine. But if the child weren't inoculated, something else might trigger the condition -- perhaps even an illness the child gets by not being protected.
California health officials must not allow parental anxieties to roll back the clock on vaccinations. Public health is guarded by so-called herd immunity, in which the vaccination of most children protects the few for whom vaccines are less effective. Herd immunity is lost when 5% to 15% of children go unvaccinated. Though state law requires that all children be up to date on their shots before entering kindergarten, there are liberal exemptions for medical, religious or "personal belief" reasons. In Los Angeles County, personal exemptions have crept up in recent years but still account for less than 1% of children. In Mendocino County, though, such exemptions now are at 5.3%, and in Nevada County, 14.4%. Parents cannot be allowed to endanger other people's children. The Legislature should revisit the "personal belief" exemption.