In certain parts of the US, vaccination rates have dropped so low that occurrences of some children’s diseases are approaching pre-vaccine levels for the first time ever. And the number of people who choose not to vaccinate their children (so-called philosophical exemptions are available in about 20 states, including Pennsylvania, Texas, and much of the West) continues to rise. In states where such opting out is allowed, 2.6 percent of parents did so last year, up from 1 percent in 1991, according to the CDC. In some communities, like California’s affluent Marin County, just north of San Francisco, non-vaccination rates are approaching 6 percent (counterintuitively, higher rates of non-vaccination often correspond with higher levels of education and wealth).
That may not sound like much, but a recent study by the Los Angeles Times indicates that the impact can be devastating. The Times found that even though only about 2 percent of California’s kindergartners are unvaccinated (10,000 kids, or about twice the number as in 1997), they tend to be clustered, disproportionately increasing the risk of an outbreak of such largely eradicated diseases as measles, mumps, and pertussis (whooping cough). The clustering means almost 10 percent of elementary schools statewide may already be at risk.
In May, The New England Journal of Medicine laid the blame for clusters of disease outbreaks throughout the US squarely at the feet of declining vaccination rates, while nonprofit health care provider Kaiser Permanente reported that unvaccinated children were 23 times more likely to get pertussis, a highly contagious bacterial disease that causes violent coughing and is potentially lethal to infants. In the June issue of the journal Pediatrics, Jason Glanz, an epidemiologist at Kaiser’s Institute for Health Research, revealed that the number of reported pertussis cases jumped from 1,000 in 1976 to 26,000 in 2004. A disease that vaccines made rare, in other words, is making a comeback. “This study helps dispel one of the commonly held beliefs among vaccine-refusing parents: that their children are not at risk for vaccine-preventable diseases,” Glanz says.
“I used to say that the tide would turn when children started to die. Well, children have started to die,” Offit says, frowning as he ticks off recent fatal cases of meningitis in unvaccinated children in Pennsylvania and Minnesota. “So now I’ve changed it to ‘when enough children start to die.’ Because obviously, we’re not there yet.”