CalScope — California's COVID-19 Antibody Study (2021-2022)
CalScope is a population-based serosurvey that helps the California Department of Public Health (CDPH) learn how many Californians have antibodies to the virus that causes COVID-19, either through infection, vaccination, or both, and how this may change over time. This information helps CDPH understand COVID-19 disease burden and will help design more effective and efficient mitigation strategies.
Through CalScope, households in selected counties were randomly invited to take a brief, anonymous survey and a free, at-home COVID-19 antibody test using a finger-prick blood sample. Counties participating in CalScope (Alameda, El Dorado, Kern, Los Angeles, Monterey, San Diego, and Shasta) were selected to represent different regions of California so that data from this study can estimate how seroprevalence varies throughout California.
The CalScope serosurvey took place in three separate waves during 2021-2022. Wave 1 was conducted from May-June 2021. Wave 2 was conducted from October 2021-February 2022, and Wave 3 was conducted from April-August 2022. As of July 29, 2022, participant enrollment in CalScope has ended.
Have questions about CalScope? Contact
Reports and Publications
U.S. Centers for Disease Control and Prevention (CDC)
California Department of Public Health (CDPH)
The following CalScope resources were created by CDPH for local partners in participating counties (Alameda, El Dorado, Kern, Los Angeles, Monterey, San Diego, and Shasta).
CalScope Fact Sheet for Local Partners - overview of study
CalScope FAQ - for agencies to respond to questions from community members
Why Calscope Is Important Flyer
- with steps for participation
*In the past, CDPH has collected information in other ways about antibodies in California from people who have had their blood tested for COVID-19. From March-June 2021, CDPH posted statewide seroprevalence estimates using antibody test data reported to CDPH by clinical laboratories and blood banks. As vaccination rates increased in California during this time period, fewer people were tested for antibodies. Additionally, blood banks stopped routine antibody testing of donors. As a result, CDPH no longer had sufficient data to produce monthly seroprevalence estimates using these data sources alone, so seroprevalence estimates were no longer posted.
Originally published on February 11, 2022