Vaccine Refusals Tied to Pertussis Outbreak

Clusters of children who didn’t get shots contributed to a major outbreak of pertussis in California, a study suggests. Pertussis is also called whooping cough. The 2010 outbreak was the largest in more than 60 years. More than 9,000 cases and 10 deaths occurred. All states require children to get vaccines before they enter kindergarten. One of the vaccines helps prevent whooping cough. But California allows exemptions for many non-medical reasons. Researchers looked at patterns of non-medical exemptions in the state. They focused on the years 2005 through 2010. They found 39 areas of the state with large clusters of exemptions. They also found 2 areas of the state that had high rates of whooping cough in 2010. Census districts in exemption clusters were 2.5 times as likely to have high rates of whooping cough as areas with fewer exemptions.