California Vaccine Preventable Disease Cases by County and Year

2001 onward, 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 the mandatory reporting system, with data subject to updates due to reporting delays.

Use Cases

• Analyze disease case trends by county and year to identify geographic and temporal hotspots for public health intervention.
• Compare case counts across specific diseases like Measles, Mumps, Pertussis, and Varicella to assess relative prevalence and outbreak patterns.
• Investigate reporting completeness by correlating case data with factors like disease severity or media attention mentioned in the limitations.

Strengths

• Data originates from a mandatory, passive reporting system mandated by the California Code of Regulations, ensuring a systematic collection process.
• Covers a multi-year time series starting from 2001, allowing for longitudinal analysis of disease trends.
• Includes data on multiple specific vaccine preventable diseases such as Measles, Mumps, Pertussis, and Varicella.

Limitations

• Case numbers likely underestimate true disease magnitude due to under-reporting from factors like delayed notification and limited specimen testing.
• Differential reporting practices among local health departments may result in inconsistent data quality across counties.
• Data is subject to retrospective updates as cases with eligible onset dates may be added or rescinded after report publication.

Provenance

Source

California Department of Public Health (CDPH) Immunization Branch.

Collection Method

Extracted from mandatory California Confidential Morbidity Reports and/or Laboratory Reports submitted to CDPH that met surveillance case definitions.

Time Range

2001 through the last indicated year prior to the 2025 update.

Freshness

Last updated on 2025-11-23.

Geography

California, United States, aggregated by county.