Out of 8200+ cases of whooping cough in California, only 10% were never vaccinated for pertussis. The link to this doc has since been password protected by @CAPublicHealth. But thanks to @WaybackMachine it remains accessible to the public. cc: @uTobian https://web.archive.org/web/20170207050527/http://www.cdph.ca.gov/programs/immunize/Documents/Pertussis%20report%204-20-2015.pdf
Pertussis-report-4-20-2015