Idaho attributes its increase in pertussis to low vaccination rates. The number of cases of pertussis (or whooping cough) in Idaho from January to July 2014 was double that for the same periods in 2012 and 2013. Among the 241 cases diagnosed through July, one infant had died, according to the Idaho Department of Health and Welfare. Rates are highest in children five to 17 years of age. Idaho has one of the lowest vaccination rates in the United States, and state health officials are urging more people to be vaccinated. Pregnant women should be vaccinated in the third trimester. Children need five doses of the vaccine from birth to six years of age. Children seven to 18 years of age who were not fully vaccinated earlier and adults who weren't vaccinated as teens need a single dose, according the Centers for Disease Control and Prevention.