It stands to reason that, were some illness spreading within a family’s local area, surely they would err on the side of protecting their own children from it if an effective preventive measure were available. If whooping cough was knocking at parents’ doors, wouldn’t that be enough to sway them toward vaccinating their kids against it?

The answer, as it happens, is no.

According to a study presented this week at the annual meeting of the Pediatric Academic Societies, vaccine rates in Washington state did not increase despite an epidemic of pertussis (whooping cough) there. That epidemic sickened thousands of individuals from October 2011 through December 2012. Over a similar span of time the Centers for Disease Control received reports of 20 pertussis-related deaths nationwide, the majority of which were in infants.

What didn’t happen in Washington during that span of time was more people choosing to vaccinate their kids against pertussis.