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Based on blood donations in the US from July 2020 through May 2021, how did infection- and vaccine-induced SARS-CoV-2 seroprevalence vary over time by demographic group and by geographic region?
In this repeated cross-sectional study that included 1 443 519 blood donation specimens from a catchment area representing 74% of the US population, estimated SARS-CoV-2 seroprevalence weighted for differences between the study sample and general population increased from 3.5% in July 2020 to 20.2% for infection-induced antibodies and 83.3% for combined infection- and vaccine-induced antibodies in May 2021. Seroprevalence differed by age, race and ethnicity, and geographic region of residence, but these differences changed over the course of the study.
Based on a sample of blood donations in the US from July 2020 through May 2021, estimated SARS-CoV-2 seroprevalence increased over time and varied by age, race and ethnicity, and geographic region.
People who have been infected with or vaccinated against SARS-CoV-2 have reduced risk of subsequent infection, but the proportion of people in the US with SARS-CoV-2 antibodies from infection or vaccination is uncertain.
To estimate trends in SARS-CoV-2 seroprevalence related to infection and vaccination in the US population.
Design, Setting, and Participants
In a repeated cross-sectional study conducted each month during July 2020 through May 2021, 17 blood collection organizations with blood donations from all 50 US states; Washington, DC; and Puerto Rico were organized into 66 study-specific regions, representing a catchment of 74% of the US population. For each study region, specimens from a median of approximately 2000 blood donors were selected and tested each month; a total of 1 594 363 specimens were initially selected and tested. The final date of blood donation collection was May 31, 2021.
Main Outcomes and Measures
Proportion of persons with detectable SARS-CoV-2 spike and nucleocapsid antibodies. Seroprevalence was weighted for demographic differences between the blood donor sample and general population. Infection-induced seroprevalence was defined as the prevalence of the population with both spike and nucleocapsid antibodies. Combined infection- and vaccination-induced seroprevalence was defined as the prevalence of the population with spike antibodies. The seroprevalence estimates were compared with cumulative COVID-19 case report incidence rates.
Among 1 443 519 specimens included, 733 052 (50.8%) were from women, 174 842 (12.1%) were from persons aged 16 to 29 years, 292 258 (20.2%) were from persons aged 65 years and older, 36 654 (2.5%) were from non-Hispanic Black persons, and 88 773 (6.1%) were from Hispanic persons. The overall infection-induced SARS-CoV-2 seroprevalence estimate increased from 3.5% (95% CI, 3.2%-3.8%) in July 2020 to 20.2% (95% CI, 19.9%-20.6%) in May 2021; the combined infection- and vaccination-induced seroprevalence estimate in May 2021 was 83.3% (95% CI, 82.9%-83.7%). By May 2021, 2.1 SARS-CoV-2 infections (95% CI, 2.0-2.1) per reported COVID-19 case were estimated to have occurred.
Conclusions and Relevance
Based on a sample of blood donations in the US from July 2020 through May 2021, vaccine- and infection-induced SARS-CoV-2 seroprevalence increased over time and varied by age, race and ethnicity, and geographic region. Despite weighting to adjust for demographic differences, these findings from a national sample of blood donors may not be representative of the entire US population.
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CME Disclosure Statement: Unless noted, all individuals in control of content reported no relevant financial relationships. If applicable, all relevant financial relationships have been mitigated.
Corresponding Author: Jefferson M. Jones, MD, MPH, CDR, US Public Health Service, Seroprevalence Team Lead, Epidemiology Task Force, Centers for Disease Control and Prevention COVID-19 Response, 1600 Clifton Rd NE, MS V18-4, Atlanta, GA 30329-4027 (firstname.lastname@example.org).
Accepted for Publication: August 19, 2021.
Published Online: September 2, 2021. doi:10.1001/jama.2021.15161
Author Contributions: Dr Opsomer had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Jones, Stone, Sulaeman, Saa, Biggerstaff, Strauss, Destree, Nguyen, Weales, Brown, Gould, Miller, Fry, Hall, Gundlapalli, Basavaraju, Patton, Simmons, Thornburg, Kleinman, Stramer, Busch.
Acquisition, analysis, or interpretation of data: Jones, Stone, Sulaeman, Fink, Dave, Levy, Di Germanio, Green, Notari, Saa, Biggerstaff, Kessler, Vassallo, Reik, Rossmann, Nguyen, Sayers, Lough, Bougie, Ritter, Latoni, Sime, Gorlin, Brown, Berney, Benoit, Miller, Freeman, Kartik, Azziz-Baumgartner, Hall, MacNeil, Gundlapalli, Basavaraju, Gerber, Patton, Custer, Williamson, Simmons, Kleinman, Stramer, Opsomer, Busch.
Drafting of the manuscript: Jones, Saa, Ritter, Miller, Freeman, Kartik, Gundlapalli, Basavaraju, Stramer, Opsomer, Busch.
Critical revision of the manuscript for important intellectual content: Jones, Stone, Sulaeman, Fink, Dave, Levy, Di Germanio, Green, Notari, Saa, Biggerstaff, Strauss, Kessler, Vassallo, Reik, Rossmann, Destree, Nguyen, Sayers, Lough, Bougie, Ritter, Latoni, Weales, Sime, Gorlin, Brown, Gould, Berney, Benoit, Miller, Fry, Azziz-Baumgartner, Hall, MacNeil, Gundlapalli, Basavaraju, Gerber, Patton, Custer, Williamson, Simmons, Thornburg, Kleinman, Stramer, Busch.
Statistical analysis: Jones, Sulaeman, Levy, Biggerstaff, Berney, Freeman, Kartik, Opsomer, Busch.
Obtained funding: Stone, Saa, Gould, Hall, Patton, Simmons, Stramer, Busch.
Administrative, technical, or material support: Jones, Stone, Sulaeman, Fink, Dave, Levy, Di Germanio, Green, Notari, Saa, Strauss, Kessler, Vassallo, Reik, Rossmann, Destree, Nguyen, Sayers, Lough, Bougie, Ritter, Latoni, Weales, Sime, Gorlin, Brown, Gould, Berney, Benoit, Miller, Azziz-Baumgartner, Hall, Gundlapalli, Basavaraju, Gerber, Patton, Custer, Williamson, Simmons, Thornburg, Stramer, Busch.
Supervision: Jones, Stone, Sulaeman, Saa, Reik, Ritter, Gould, Fry, Hall, MacNeil, Gundlapalli, Patton, Custer, Thornburg, Stramer, Opsomer, Busch.
Conflict of Interest Disclosures: The Gulf Coast Regional Blood Center uses Roche assays for testing and Dr Rossmann reported serving as principal investigator on Roche blood donor testing, for which she received no direct compensation outside the submitted work. Dr Sime reported collecting convalescent plasma from blood donors for LifeServe Blood Center during the time samples were collected outside the submitted work. Dr Kartik reported receiving personal fees from Brigham and Women’s Hospital and PathAI outside the submitted work. Dr Custer reported receiving personal fees and grants from Grifols Diagnostic Solutions outside the submitted work. Dr Kleinman reported receiving personal fees from Creative Testing Solutions and Roche Molecular Systems outside the submitted work. Dr Stramer reported receiving a contract from the CDC via Vitalant Research Institute outside the submitted work. Dr Busch reported being an employee of Vitalant Research Institute and serving on the medical advisory board for Creative Testing Systems; Vitalant Research Institute receives research funds and reagents for studies from Ortho and Roche and Dr Busch has presented on behalf of both companies at meetings in the past with travel support but does not receive personal compensation from these or other SARS-CoV-2 test manufacturing companies. No other disclosures were reported.
Funding/Support: This study was funded by the CDC.
Role of the Funder/Sponsor: CDC employees contributed to 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. The CDC did not have the right to veto publication or to control the decision regarding to which journal the study was submitted.
Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the CDC.
Additional Contributions: We thank members from Vitalant Research Institute, Westat, the American Red Cross, each of the 17 participating blood collection organizations and 10 testing laboratories, and Georgia Tech Research Institute for their assistance on this study.
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