Whooping Cough (part 2)

Maryn, over at Superbug, has a much better post than mine about pertussis. Here's the pertinent bit:

Because vaccine immunity fades, pertussis is always with us: in good years, about 1,000 cases across the United States. Lately, though, we're in bad years. Pertussis cases are rising dramatically, in Alabama, Georgia, Arkansas, Texas, South Carolina, Michigan, Oregon and Ohio. The worst by far is California, where so far this year almost 1,500 cases of pertussis have been reported and another 700 are suspected — compared to 258 for the same time period in 2009.
...
Work published last year by several scientists at Kaiser Permanente of Colorado found that unvaccinated children were 23 times more likely to contract pertussis than vaccinated ones. (Glanz, McClure, Magid et al., Pediatrics 2009, doi:10.1542/peds.2008-2150.) And yet, as numerous stories (LA Times, MedPage Today) have pointed out, California's epidemic has blossomed in a state that gives some of the most generous "personal belief exemptions" from vaccination — and the epidemic's worst hot spots neatly correlate with the most concentrated areas of vaccine refusal.

23 times! Parents are making medical choices that lead to their kids being 23 times more likely to get sick!