This graph is from the California Department of Public Health . It is based on demographics and age groups that contracted Pertussis (Whooping Cough) in 2010.
Now there was a total of 7,824 reported cases of Pertussis out of a population of 37,253,956 people living in California according to the 2010 US Census.
And as it's fairly easy to tell over 75% of the cases are happening in infants under 6 months of age. The Federally listed incidences of Pertussis are 78% in the under one year age group.
So, what idiot in the California Legislature thought it was such a great idea to have it mandated for 7th graders who have a less than 4% chance of catching this disease, to have to get this vaccine?