Vaccine Preventable Disease Cases by County and Year

These data contain counts of vaccine preventable disease cases among California residents by county, disease, and year. The California Department of Public Health (CDPH) maintains a mandatory, passive reporting system for a list(1) of communicable disease cases and outbreaks. The CDPH Immunization Branch conducts surveillance for vaccine preventable diseases. Health care providers and laboratories are mandated to report cases or suspected cases of these communicable diseases to their local health department (LHD). LHDs are also mandated to report these cases to CDPH. ## Materials and Methods ### Case data sources and inclusion criteria Data were extracted on communicable disease cases with an estimated onset or diagnosis date from 2001 through the last year indicated, from California Confidential Morbidity Reports and/or Laboratory Reports that were submitted to CDPH and which met the surveillance case definition for that disease.(2) Because of inherent delays in case reporting and depending on the length of follow-up of clinical, laboratory and epidemiologic investigation, cases with eligible onset dates may be added or rescinded after the date of this report. ### Definitions In general, we defined a case as laboratory and/or clinical evidence of infection or disease in a person that satisfied the communicable disease surveillance case definition published by the United States (US) Centers for Disease Control and Prevention (CDC) or by the Council of State and Territorial Epidemiologists (CSTE) at the time the case was reported. ## Limitations ### Completeness of reporting The numbers of disease cases in this report are likely to underestimate the true magnitude of disease. Among factors that may contribute to under-reporting are: delays in notification, limited collection or appropriate testing of specimens, health care seeking behavior among ill persons, limited resources and competing priorities in LHDs, and lack of reporting by clinicians and laboratories. Among factors that may contribute to changes in reporting are disease severity, the availability of new or less expensive diagnostic tests, changes in the case definition by CDC or CDPH, changes in mandatory reporting requirements, recent media or public attention, and active surveillance activities. Differential reporting practices among LHDs may also result in inconsistent reporting of patient information. ### References 1. California Code of Regulations, Title 17, Sections 2500 and 2505 https://www.cdph.ca.gov/Programs/CID/DCDC/CDPH%20Document%20Library/ReportableDiseases.pdf 2. Center for Disease Control and Prevention, National Notifiable Diseases Surveillance System https://ndc.services.cdc.gov/