“THEY hang out in pockets,” says Richard Pan, a Sacramento paediatrician and member of California’s legislature. He is referring to parents who, invoking a “philosophical exemption”, opt not to give their children the state-recommended vaccinations. In some pockets, such as the rural foothills of California’s Sierra Nevada, they may belong to the conservative don’t-tread-on-me crowd that distrusts all government recommendations simply because they come from the government. In others, such as the liberal organic-food-and-yoga belt along the coast, parents may forswear vaccines because they see the shots as dangerous, and the diseases they protect against as mild.
These local concentrations of unvaccinated children pose a growing risk to public health. For the most common shots, vaccination rates for America overall, and even California, are still above 90%, at or near the levels considered necessary to provide “herd immunity” for a population. But in places the rates have been falling for almost a decade. In many counties, towns and nursery schools--within Washington state, Oregon, Vermont and California, especially—vaccination rates are now far below the herd-immunity level.
This trend, predictably, is leading to the resurgence of diseases considered vanquished long ago. In 2010, for example, California had an outbreak of whooping cough, which at its height put 455 babies in hospital and killed ten of them. Elsewhere there have been outbreaks of measles.
The case for vaccination is clear. First, it makes the vaccinated individual either immune or resistant to a disease. Second, and more important, it interferes with contagion and thus makes the entire community safer, including those members, like newborn babies or the very sick, who cannot be vaccinated for medical reasons. The vaccination rate for herd immunity varies by disease, but usually falls between 85% and 95%.
The case against vaccination, by contrast, is not clear. One view seems to be that the diseases in question merely give you a rash and are a nuisance, whereas the vaccines will make your child autistic. That particular myth, still peddled on the internet, originated with Andrew Wakefield, a British doctor, who published a paper in 1998 that suggested a link between the common MMR shot (against measles, mumps and rubella) and autism. The paper has since been entirely discredited, and Dr Wakefield censured.