Estimated SARS-CoV-2 Seroprevalence in the US | Infectious Diseases | JN Learning | AMA Ed Hub [Skip to Content]
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Key Points

Question  What proportion of persons across 52 US jurisdictions had detectable antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from July to September 2020?

Findings  In this repeated, cross-sectional study of 177 919 residual clinical specimens, the estimated percentage of persons in a jurisdiction with detectable SARS-CoV-2 antibodies ranged from fewer than 1% to 23%. Over 4 sampling periods in 42 of 49 jurisdictions with calculated estimates, fewer than 10% of people had detectable SARS-CoV-2 antibodies.

Meaning  While SARS-CoV-2 antibody prevalence estimates varied widely across jurisdictions, most people in the US did not have evidence of previous SARS-CoV-2 infection.

Abstract

Importance  Case-based surveillance of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection likely underestimates the true prevalence of infections. Large-scale seroprevalence surveys can better estimate infection across many geographic regions.

Objective  To estimate the prevalence of persons with SARS-CoV-2 antibodies using residual sera from commercial laboratories across the US and assess changes over time.

Design, Setting, and Participants  This repeated, cross-sectional study conducted across all 50 states, the District of Columbia, and Puerto Rico used a convenience sample of residual serum specimens provided by persons of all ages that were originally submitted for routine screening or clinical management from 2 private clinical commercial laboratories. Samples were obtained during 4 collection periods: July 27 to August 13, August 10 to August 27, August 24 to September 10, and September 7 to September 24, 2020.

Exposures  Infection with SARS-CoV-2.

Main Outcomes and Measures  The proportion of persons previously infected with SARS-CoV-2 as measured by the presence of antibodies to SARS-CoV-2 by 1 of 3 chemiluminescent immunoassays. Iterative poststratification was used to adjust seroprevalence estimates to the demographic profile and urbanicity of each jurisdiction. Seroprevalence was estimated by jurisdiction, sex, age group (0-17, 18-49, 50-64, and ≥65 years), and metropolitan/nonmetropolitan status.

Results  Of 177 919 serum samples tested, 103 771 (58.3%) were from women, 26 716 (15.0%) from persons 17 years or younger, 47 513 (26.7%) from persons 65 years or older, and 26 290 (14.8%) from individuals living in nonmetropolitan areas. Jurisdiction-level seroprevalence over 4 collection periods ranged from less than 1% to 23%. In 42 of 49 jurisdictions with sufficient samples to estimate seroprevalence across all periods, fewer than 10% of people had detectable SARS-CoV-2 antibodies. Seroprevalence estimates varied between sexes, across age groups, and between metropolitan/nonmetropolitan areas. Changes from period 1 to 4 were less than 7 percentage points in all jurisdictions and varied across sites.

Conclusions and Relevance  This cross-sectional study found that as of September 2020, most persons in the US did not have serologic evidence of previous SARS-CoV-2 infection, although prevalence varied widely by jurisdiction. Biweekly nationwide testing of commercial clinical laboratory sera can play an important role in helping track the spread of SARS-CoV-2 in the US.

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Article Information

Accepted for Publication: November 6, 2020.

Published Online: November 24, 2020. doi:10.1001/jamainternmed.2020.7976

Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2020 Bajema KL et al. JAMA Internal Medicine.

Corresponding Author: Kristina L. Bajema, MD, MSc, US Centers for Disease Control and Prevention (CDC), 1600 Clifton Rd NE, Mailstop H24-6, Atlanta, GA 30329 (pgz0@cdc.gov).

Author Contributions: Drs Bajema and Edens had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Bajema, Iachan, Havers, Harding, Fry, Hall, Gundlapalli, Thornburg, Petersen, Edens.

Acquisition, analysis, or interpretation of data: Bajema, Wiegand, Cuffe, Patel, Iachan, Lim, Lee, Moyse, Harding, Kelly, Biel, Deng, Meyer, Mathur, Kyle, Gundlapalli, Thornburg, Petersen, Edens.

Drafting of the manuscript: Bajema, Wiegand, Cuffe, Patel, Iachan, Harding, Edens.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Bajema, Wiegand, Iachan, Lim, Lee, Harding, Kelly, Biel, Deng, Edens.

Obtained funding: Bajema, Cuffe, Havers, Fry, Hall, Gundlapalli, Petersen, Edens.

Administrative, technical, or material support: Bajema, Wiegand, Cuffe, Patel, Moyse, Havers, Fry, Hall, Meyer, Mathur, Kyle, Gundlapalli, Thornburg, Petersen, Edens.

Supervision: Iachan, Havers, Fry, Hall, Mathur, Meyer, Thornburg, Edens.

Conflict of Interest Disclosures: ICF, Inc, Quest Diagnostics, and BioReference Laboratories were awarded federal contracts from CDC for the execution of this project. No other disclosures were reported.

Funding/Support: This work was supported by CDC (Atlanta, Georgia).

Role of the Funder/Sponsor: CDC had a role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Disclaimer: The findings and conclusions in the article are those of the authors and do not necessarily represent the official position of CDC.

Additional Contributions: We thank Gabriele Richardson, PhD, CDC, for mapping support as well as other members of CDC for administrative and technical support: Teresa Kinley, MS, Melissa Carter, PhD, Lauren Peel, JD, Adrean Mabry, BS, Saraine Ross, BA, Jasmine Chaitram, MPH, Alex Hoffmaster, PhD, Subbian Panayampalli, PhD, William Duck, MS, Eduardo Azziz-Baumgartner, MD, Adam MacNeil, PhD. We thank Quest and BioReference for testing specimens. From Quest: Brian Jaffa, MS, Caterina Powell, BS, Rebecca Parsons, BS, Brian Young, AA, Carol Bledsoe, Nicki Sylvester, MBA, Bonnie Bouck, AA, Georgia Schoemaker, BS, Stephanie Buchler, Larry Hirsch, BS, Narshimlu Ramdas, BTech, Neelima Donur, MS, Jeff Crawford, BS. From BioReference: James Weisberger, MD, Dan McNichol, MBA, Ada Gazzillo, BS, Nick Cetani, MS, Cesar Abril, MBA, Angela Canada, BS, Amal Abadeer, BA, and Pamela Depuy. These individuals were not compensated directly by CDC for their participation in this specific study.

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