My lede:

Some parents, concerned that vaccines could injure their children, choose to forgo or delay childhood immunizations. One barrier to convincing on-the-fence parents of the benefits of vaccines is that the downside of refusing seems minimal. Parents who opt out often have good reason to believe that herd immunity will protect their children from harm.

But a new study finds that, at least with regard to pertussis, vaccine refusal is not risk-free. Children whose parents refused the pertussis vaccine were 23 times likelier to contract the disease than were immunized children, according to a June Pediatrics study of 156 pertussis cases drawn from the Kaiser Permanente Colorado health plan. One in 10 pertussis cases was due to vaccine refusal, the study found (pediatrics.aappublications.org/cgi/content/abstract/123/6/1446/).

The whole shebang.