Researchers studied the 2010 epidemic of pertussis in California. •They selected a random sample of 682 medical records of California children ages 4 to 10 who had been diagnosed with pertussis.
They also selected a random sample of 2016 medical records of California children in the same age group who had received care from the same clinicians on the same day but were not diagnosed with pertussis.
They found that children diagnosed with pertussis were much more likely* to have not received any pertussis vaccine, to have not received all recommended doses of the vaccine, or to have had a longer interval of time since their last vaccination. doi:10.1001/jama.2012.14939 What is the study's main objective and how does the study design help address it?
What can we reasonably conclude from this study?