Further, in 2012, more than 41,000 pertussis cases and 18 deaths due to pertussis were reported to the CDC, also the largest number of cases in the United States since 1959.2 Most vaccine-preventable diseases are contagious and can be serious in children and adults with whom they have contact. Therefore, it is important that school-aged children are up-to-date on all annual immunizations prior to each school year