#SARS-CoV-2-specific #antibody #detection for #seroepidemiology: a multiplex analysis approach accounting for accurate #seroprevalence (J Infect Dis., abstract)

[Source: Journal of Infectious Diseases, full page: (LINK). Abstract, edited.]

SARS-CoV-2-specific antibody detection for sero-epidemiology: a multiplex analysis approach accounting for accurate seroprevalence

Gerco den Hartog, Rutger M Schepp, Marjan Kuijer, Corine GeurtsvanKessel, Josine van Beek, Nynke Rots, Marion P G Koopmans, Fiona R M van der Klis, Robert S van Binnendijk

The Journal of Infectious Diseases, jiaa479, https://doi.org/10.1093/infdis/jiaa479

Published: 08 August 2020




The COVID-19 pandemic necessitates a better understanding of the kinetics of antibody production induced by infection with SARS-CoV-2. We aimed to develop a high throughput multiplex assay to detect antibodies to SARS-CoV-2 to assess immunity to the virus in the general population.


Spike protein subunits S1 and RBD, and Nucleoprotein were coupled to distinct microspheres. Sera collected before the emergence of SARS-CoV-2 (N=224), and of non-SARS-CoV-2 influenza-like illness (N=184), and laboratory-confirmed cases of SARS-CoV-2 infection (N=115) with various severity of COVID-19 were tested for SARS-CoV-2-specific concentrations of IgG.


Our assay discriminated SARS-CoV-2-induced antibodies and those induced by other viruses. The assay obtained a specificity between 95.1 and 99.0% with a sensitivity ranging from 83.6-95.7%. By merging the test results for all 3 antigens a specificity of 100% was achieved with a sensitivity of at least 90%. Hospitalized COVID-19 patients developed higher IgG concentrations and the rate of IgG production increased faster compared to non-hospitalized cases.


The bead-based serological assay for quantitation of SARS-CoV-2-specific antibodies proved to be robust and can be conducted in many laboratories. Finally, we demonstrated that testing of antibodies against different antigens increases sensitivity and specificity compared to single antigen-specific IgG determination.

COVID-19, IgG, Spike S1, RBD, Nucleoprotein, endemic coronavirus, multiplex bead-based immune assay, specificity, sensitivity, Influenza-like Illness (ILI)

Topic:  epidemiology – coronavirus – antibody formation – antigens – immunity – laboratory – microspheres – nucleoproteins – protein subunits – serologic tests – immunoglobulin g – infections – antibodies – kinetics – viruses – severe acute respiratory syndrome – serum – flu-like illness – laboratory test finding – seroprevalence – sars-cov-2 –
covid-19 – coronavirus pandemic

Issue Section: Major Article

This content is only available as a PDF.

© The Author(s) 2020. Published by Oxford University Press for the Infectious Diseases Society of America.

This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs licence (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reproduction and distribution of the work, in any medium, provided the original work is not altered or transformed in any way, and that the work is properly cited. For commercial re-use, please contact journals.permissions@oup.com

Keywords: SARS-CoV-2; COVID-19; Serology; Seroprevalence.


Cross – #reactivity towards #SARS-CoV-2: the potential role of low-pathogenic #human #coronaviruses (Lancet Microbe, summary)

[Source: Lancet Microbe, full page: (LINK). Summary, edited.]

Cross-reactivity towards SARS-CoV-2: the potential role of low-pathogenic human coronaviruses

Zhongren Ma, Pengfei Li, Yuepeng Ji, Aqsa Ikram, Qiuwei Pan

Open Access | Published: August, 2020 | DOI: https://doi.org/10.1016/S2666-5247(20)30098-7


The human body is capable of producing antibodies in response to severe acute  respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the causative agent of  COVID-19. The principle of antigen-antibody reaction has been widely explored to  develop enzyme immunoassays for studying seroprevalence. Kelvin Kai-Wang To and  colleagues1  found a seropositive rate of 2·73% (53 of 1938 serum samples) in SARS-CoV-2  enzyme immunoassays for individuals who had probably not been exposed to the  virus. This finding raises the possibility of antibody cross-reactivity with other human  coronaviruses.


Keywords: SARS-CoV-2; COVID-19; Seroprevalence; Coronavirus.


#Prevalence of #SARS-CoV-2 #Antibodies in #HealthCare Personnel in the #NYC Area (JAMA, abstract)

[Source: JAMA, full page: (LINK). Abstract, edited.]

Prevalence of SARS-CoV-2 Antibodies in Health Care Personnel in the New York City Area

Joseph Moscola, PA, MBA1; Grace Sembajwe, DSc, MSc, CIH2; Mark Jarrett, MD, MBA, MS1; et alBruce Farber, MD3; Tylis Chang, MD4; Thomas McGinn, MD, MPH2; Karina W. Davidson, PhD, MASc2; for the Northwell Health COVID-19 Research Consortium

JAMA. Published online August 6, 2020. doi:10.1001/jama.2020.14765


The greater New York City (NYC) area, including the 5 boroughs and surrounding counties, has a high incidence of coronavirus disease 2019 (COVID-19),1 and health care personnel (HCP) working there have a high exposure risk. HCP have expressed concerns about access to testing so that infection spread to patients, other HCP, and their families can be minimized.2 The Northwell Health System, the largest in New York State, sought to address this concern by offering voluntary antibody testing to all HCP. We investigated the prevalence of antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among HCP and associations with demographics, primary work location and type, and suspicion of virus exposure.


Keywords: SARS-CoV-2; COVID-19; Serology; Seroprevalence; HCWs; NYC; USA.


Repeated leftover #serosurvey of #SARS-CoV-2 #IgG #antibodies, #Greece, March and April 2020 (Euro Surveill., abstract)

[Source: Eurosurveillance, full page: (LINK). Abstract, edited.]

Repeated leftover serosurvey of SARS-CoV-2 IgG antibodies, Greece, March and April 2020

Zacharoula Bogogiannidou1 , Alexandros Vontas1 , Katerina Dadouli1 , Maria A Kyritsi1 , Soteris Soteriades1 , Dimitrios J Nikoulis1 , Varvara Α Mouchtouri1 , Michalis Koureas1 , Evangelos I Kazakos2 , Emmanouil G Spanos1 , Georgia Gioula3 , Evangelia E Ntzani4,5,6 , Alexandros A Eleftheriou4 , Alkiviadis Vatopoulos7 , Efthimia Petinaki8 , Vassiliki Papaevangelou9 , Matthaios Speletas10 , Sotirios Tsiodras11 , Christos Hadjichristodoulou1

Affiliations: 1 Laboratory of Hygiene and Epidemiology, Faculty of Medicine, University of Thessaly, Larissa, Greece; 2 Faculty of Midwifery, School of Health Sciences, University of Western Macedonia, Kozani, Greece; 3 National Influenza Reference Laboratory for Northern Greece, Microbiology Department, Medical School, Aristotle University of Thessaloniki, Thessaloniki, Greece; 4 Department of Hygiene and Epidemiology, University of Ioannina Faculty of Medicine, Ioannina, Greece; 5 Center for Evidence Synthesis in Health, Department of Health Services, Policy and Practice, School of Public Health, Brown University, Providence, United States; 6 Institute of Biosciences, University Research Center of loannina, Ioannina, Greece; 7 Department of Public Health Policy, School of Public Health, University of West Attica, Athens, Greece; 8 Department of Microbiology, University Hospital of Larissa, University of Thessaly, Larissa, Greece; 9 Third Department of Paediatrics, National and Kapodistrian University of Athens, School of Medicine, Attikon University Hospital, Athens, Greece; 10 Department of Immunology and Histocompatibility, Faculty of Medicine, University of Thessaly, Larissa, Greece; 11 Fourth Department of Internal Medicine, National and Kapodistrian University of Athens, School of Medicine, Attikon University Hospital, Athens, Greece

Correspondence:  Christos Hadjichristodoulou

Citation style for this article: Bogogiannidou Zacharoula , Vontas Alexandros , Dadouli Katerina , Kyritsi Maria A , Soteriades Soteris , Nikoulis Dimitrios J , Mouchtouri Varvara Α , Koureas Michalis , Kazakos Evangelos I , Spanos Emmanouil G , Gioula Georgia , Ntzani Evangelia E , Eleftheriou Alexandros A , Vatopoulos Alkiviadis , Petinaki Efthimia , Papaevangelou Vassiliki , Speletas Matthaios , Tsiodras Sotirios , Hadjichristodoulou Christos . Repeated leftover serosurvey of SARS-CoV-2 IgG antibodies, Greece, March and April 2020. Euro Surveill. 2020;25(31):pii=2001369. https://doi.org/10.2807/1560-7917.ES.2020.25.31.2001369

Received: 12 Jul 2020;   Accepted: 03 Aug 2020



A serosurvey of IgG antibodies against severe acute respiratory coronavirus 2 (SARS-CoV-2) was performed during March and April 2020. Among 6,586 leftover sera, 24 (0.36%) were positive, with higher prevalence in females, older individuals and residents of large urban areas. Seroprevalence was estimated at 0.02% and 0.25%, respectively, in March and April, infection fatality rate at 2.66% and 0.54%. Our findings confirm low COVID-19 incidence in Greece and possibly the effectiveness of early measures.

©  This work is licensed under a Creative Commons Attribution 4.0 International License.

Keywords: SARS-CoV-2; COVID-19; Serology; Seroprevalence; Greece.


#Risk of #COVID19 in #HCWs in #Denmark: an observational cohort study (Lancet Infect Dis., abstract)

[Source: The Lancet Infectious Diseases, full page: (LINK). Abstract, edited.]

Risk of COVID-19 in health-care workers in Denmark: an observational cohort study

Prof Kasper Iversen, DMS, Prof Henning Bundgaard, DMSc, Rasmus B Hasselbalch, MD, Jonas H Kristensen, MD, Pernille B Nielsen, MD, Mia Pries-Heje, MD, Andreas D Knudsen, MD, Casper E Christensen, PhD, Kamille Fogh, MD, Jakob B Norsk, MD, Prof Ove Andersen, DMSc, Thea K Fischer, DMSc, Claus Antonio Juul Jensen, MD, Margit Larsen, PhD, Prof Christian Torp-Pedersen, DMSc, Prof Jørgen Rungby, DMSc, Sisse B Ditlev, PhD, Ida Hageman, MD, Rasmus Møgelvang, PhD, Christoffer E Hother, MD, Mikkel Gybel-Brask, PhD, Erik Sørensen, MD, Lene Harritshøj, PhD, Prof Fredrik Folke, PhD, Curt Sten, MD, Prof Thomas Benfield, DMSc, Susanne Dam Nielsen, DMSc, Prof Henrik Ullum, PhD

Published: August 03, 2020 | DOI: https://doi.org/10.1016/S1473-3099(20)30589-2




Health-care workers are thought to be highly exposed to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We aimed to investigate the prevalence of antibodies against SARS-CoV-2 in health-care workers and the proportion of seroconverted health-care workers with previous symptoms of COVID-19.


In this observational cohort study, screening was offered to health-care workers in the Capital Region of Denmark, including medical, nursing, and other students who were associated with hospitals in the region. Screening included point-of-care tests for IgM and IgG antibodies against SARS-CoV-2. Test results and participant characteristics were recorded. Results were compared with findings in blood donors in the Capital Region in the study period.


Between April 15 and April 23, 2020, we screened 29 295 health-care workers, of whom 28 792 (98·28%) provided their test results. We identified 1163 (4·04% [95% CI 3·82–4·27]) seropositive health-care workers. Seroprevalence was higher in health-care workers than in blood donors (142 [3·04%] of 4672; risk ratio [RR] 1·33 [95% CI 1·12–1·58]; p<0·001). Seroprevalence was higher in male health-care workers (331 [5·45%] of 6077) than in female health-care workers (832 [3·66%] of 22 715; RR 1·49 [1·31–1·68]; p<0·001). Frontline health-care workers working in hospitals had a significantly higher seroprevalence (779 [4·55%] of 16 356) than health-care workers in other settings (384 [3·29%] of 11 657; RR 1·38 [1·22–1·56]; p<0·001). Health-care workers working on dedicated COVID-19 wards (95 [7·19%] of 1321) had a significantly higher seroprevalence than other frontline health-care workers working in hospitals (696 [4·35%] of 15 983; RR 1·65 [1·34–2·03]; p<0·001). 622 [53·5%] of 1163 seropositive participants reported symptoms attributable to SARS-CoV-2. Loss of taste or smell was the symptom that was most strongly associated with seropositivity (377 [32·39%] of 1164 participants with this symptom were seropositive vs 786 [2·84%] of 27 628 without this symptom; RR 11·38 [10·22–12·68]). The study is registered at ClinicalTrials.gov, NCT04356560.


The prevalence of health-care workers with antibodies against SARS-CoV-2 was low but higher than in blood donors. The risk of SARS-CoV-2 infection in health-care workers was related to exposure to infected patients. More than half of seropositive health-care workers reported symptoms attributable to COVID-19.


Lundbeck Foundation.

Keywords: SARS-CoV-2; COVID-19; Serology; Seroprevalence; HCWs; Denmark.


#Seroprevalence of #SARS-CoV-2 and Infection #Fatality Ratio, #Orleans and Jefferson Parishes, #Louisiana, #USA, May 2020 (Emerg Infect Dis., abstract)

[Source: US Centers for Disease Control and Prevention (CDC), Emerging Infectious Diseases Journal, full page: (LINK). Abstract, edited.]

Volume 26, Number 11—November 2020 | Research Letter

Seroprevalence of SARS-CoV-2 and Infection Fatality Ratio, Orleans and Jefferson Parishes, Louisiana, USA, May 2020

Amy K. Feehan  , Daniel Fort, Julia Garcia-Diaz, Eboni Price-Haywood, Cruz Velasco, Eric Sapp, Dawn Pevey, and Leonardo Seoane

Author affiliations: Ochsner Clinic Foundation, New Orleans, Louisiana, USA (A.K. Feehan, D. Fort, J. Garcia-Diaz, E. Price-Haywood, C. Velasco, D. Pevey, L. Seoane); University of Queensland Ochsner Clinical School, New Orleans (A.K. Feehan, J. Garcia-Diaz, E. Price-Haywood, L. Seoane); Public Democracy, Arlington, Virginia, USA (E. Sapp); Louisiana State University Health Science Center–Shreveport, Shreveport, Louisiana, USA (L. Seoane)



Using a novel recruitment method and paired molecular and antibody testing for severe acute respiratory syndrome coronavirus 2 infection, we determined seroprevalence in a racially diverse municipality in Louisiana, USA. Infections were highly variable by ZIP code and differed by race/ethnicity. Overall census-weighted seroprevalence was 6.9%, and the calculated infection fatality ratio was 1.63%.

Keywords: SARS-CoV-2; COVID-19; Serology; Seroprevalence; Louisiana; USA.


#Seroprevalence of #SARS-CoV-2–Specific #Antibodies, #Faroe Islands (Emerg Infect Dis., abstract)

[Source: US Centers for Disease Control and Prevention (CDC), Emerging Infectious Diseases Journal, full page: (LINK). Abstract, edited.]

Volume 26, Number 11—November 2020 | Research Letter

Seroprevalence of SARS-CoV-2–Specific Antibodies, Faroe Islands

Maria Skaalum Petersen  , Marin Strøm, Debes Hammershaimb Christiansen, Jógvan Páll Fjallsbak, Eina Hansen Eliasen, Malan Johansen, Anna Sofía Veyhe, Marnar Fríðheim Kristiansen, Shahin Gaini, Lars Fodgaard Møller, Bjarni Steig, and Pál Weihe

Author affiliations: University of the Faroe Islands, Tórshavn, Faroe Islands (M.S. Petersen, M. Strøm, E.H. Eliasen, M. Johansen, A.S. Veyhe, M.F. Kristiansen, S. Gaini, P. Weihe); The Faroese Hospital System, Tórshavn (M.S. Petersen, E.H. Eliasen, M. Johansen, A.S. Veyhe, P. Weihe); Faroese Food and Veterinary Authority, Tórshavn, (D.H. Christiansen, J.P. Fjallsbak); National Hospital of the Faroe Islands, Tórshavn, (M.F. Kristiansen, S. Gaini, B. Steig); COVID-19 Task Force, Ministry of Health, Tórshavn (M.F. Kristiansen, B. Steig); Odense University Hospital, Odense, Denmark (S. Gaini); University of Southern Denmark, Odense (S. Gaini); Chief Medical Officer Office, Tórshavn (L.F. Møller)



We conducted a nationwide study of the prevalence of severe acute respiratory syndrome coronavirus 2 infection in the Faroe Islands. Of 1,075 randomly selected participants, 6 (0.6%) tested seropositive for antibodies to the virus. Adjustment for test sensitivity and specificity yielded a 0.7% prevalence. Our findings will help us evaluate our public health response.

Keywords: SARS-CoV-2; COVID-19; Serology; Seroprevalence; Denmark.


#Antibody #responses to #SARS‐CoV‐2 in healthy individuals returning to #Shenzhen (J Med Virol., abstract)

[Source: Journal of Medical Virology, full page: (LINK). Abstract, edited.]

Antibody responses to SARS‐CoV‐2 in healthy individuals returning to Shenzhen

Cantong Zhang,  Liancheng Lin,  Donge Tang,  Fuju Liu,  Meng Li, Qiongying Li, Zhaoxiang Deng,  Guohai Chu,  Dayong Gu,  Yong Dai

First published: 25 July 2020 | DOI:  https://doi.org/10.1002/jmv.26355

This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/jmv.26355




To verify reliability of antibody detection and investigate population immunity to SARS‐CoV‐2 in the local Chinese population.

Design, Setting, and Participants

This was a cross‐sectional study that was conducted in Shenzhen to detect anti‐coronavirus antibodies including, IgG, IgM, and IgA. In the COVID‐19 group, 9 patients were enrolled after diagnosis. In the control group, 1589 individuals without clinical symptoms (cough, fever, and fatigue) and returning from outside Shenzhen were enrolled. The first study enrollment occurred at the end of February 2020; the final study visit was March 18, 2020.


In the COVID‐19 group, the 7 of 9 patients were positive for IgM, IgG, and IgA. Meanwhile, 6 of the 1589 healthy individuals were found to be weakly positive for IgG. According to SARS‐CoV‐2 nucleic acid tests, the 6 individuals were all negative.


Strong supplemental support for clinical information can be provided by antibody detection, especially for IgA. According to comparison with overseas reports, the infection rate of the Chinese population outside Shenzhen, China, is significantly low, so most of the population in China is still susceptible. Hence, social distancing measures are still inevitable until a vaccine is developed successfully.

This article is protected by copyright. All rights reserved.

Keywords: SARS-CoV-2; COVID-19; Serology; Seroprevalence; China.


Point-of-care #serological #assays for delayed #SARS-CoV-2 case #identification among #HCWs in the #UK: a prospective multicentre cohort study (Lancet Resp Med., abstract)

[Source: Lancet Respiratory Medicine, full page: (LINK). Abstract, edited.]

Point-of-care serological assays for delayed SARS-CoV-2 case identification among health-care workers in the UK: a prospective multicentre cohort study

Capt Scott J C Pallett, MBBS, Michael Rayment, FRCP, Aatish Patel, MBBS, Sophia A M Fitzgerald-Smith, MBChB, Sarah J Denny, MBBS, Esmita Charani, PhD, Annabelle L Mai, MSc, Kimberly C Gilmour, PhD, James Hatcher, FRCPath, Christopher Scott, FRCP, Paul Randell, MBBCh, Nabeela Mughal, FRCPath, Rachael Jones, FRCP, Luke S P Moore, PhD †, Gary W Davies, MD †

Published: July 24, 2020 | DOI: https://doi.org/10.1016/S2213-2600(20)30315-5




Health-care workers constitute a high-risk population for acquisition of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Capacity for acute diagnosis via PCR testing was limited for individuals with mild to moderate SARS-CoV-2 infection in the early phase of the COVID-19 pandemic and a substantial proportion of health-care workers with suspected infection were not tested. We aimed to investigate the performance of point-of-care and laboratory serology assays and their utility in late case identification, and to estimate SARS-CoV-2 seroprevalence.


We did a prospective multicentre cohort study between April 8 and June 12, 2020, in two phases. Symptomatic health-care workers with mild to moderate symptoms were eligible to participate 14 days after onset of COVID-19 symptoms, as per the Public Health England (PHE) case definition. Health-care workers were recruited to the asymptomatic cohort if they had not developed PHE-defined COVID-19 symptoms since Dec 1, 2019. In phase 1, two point-of-care lateral flow serological assays, the Onsite CTK Biotech COVID-19 split IgG/IgM Rapid Test (CTK Bitotech, Poway, CA, USA) and the Encode SARS-CoV-2 split IgM/IgG One Step Rapid Test Device (Zhuhai Encode Medical Engineering, Zhuhai, China), were evaluated for performance against a laboratory immunoassay (EDI Novel Coronavirus COVID-19 IgG ELISA kit [Epitope Diagnostics, San Diego, CA, USA]) in 300 samples from health-care workers and 100 pre-COVID-19 negative control samples. In phase 2 (n=6440), serosurveillance was done among 1299 (93·4%) of 1391 health-care workers reporting symptoms, and in a subset of asymptomatic health-care workers (405 [8·0%] of 5049).


There was variation in test performance between the lateral flow serological assays; however, the Encode assay displayed reasonable IgG sensitivity (127 of 136; 93·4% [95% CI 87·8–96·9]) and specificity (99 of 100; 99·0% [94·6–100·0]) among PCR-proven cases and good agreement (282 of 300; 94·0% [91·3–96·7]) with the laboratory immunoassay. By contrast, the Onsite assay had reduced sensitivity (120 of 136; 88·2% [95% CI 81·6–93·1]) and specificity (94 of 100; 94·0% [87·4–97·8]) and agreement (254 of 300; 84·7% [80·6–88·7]). Five (7%) of 70 PCR-positive cases were negative across all assays. Late changes in lateral flow serological assay bands were recorded in 74 (9·3%) of 800 cassettes (35 [8·8%] of 400 Encode assays; 39 [9·8%] of 400 Onsite assays), but only seven (all Onsite assays) of these changes were concordant with the laboratory immunoassay. In phase 2, seroprevalence among the workforce was estimated to be 10·6% (95% CI 7·6–13·6) in asymptomatic health-care workers and 44·7% (42·0–47·4) in symptomatic health-care workers. Seroprevalence across the entire workforce was estimated at 18·0% (95% CI 17·0–18·9).


Although a good positive predictive value was observed with both lateral flow serological assays and ELISA, this agreement only occurred if the pre-test probability was modified by a strict clinical case definition. Late development of lateral flow serological assay bands would preclude postal strategies and potentially home testing. Identification of false-negative results among health-care workers across all assays suggest caution in interpretation of IgG results at this stage; for now, testing is perhaps best delivered in a clinical setting, supported by government advice about physical distancing.



Keywords: SARS-CoV-2; COVID-19; Serology; Seroprevalence; HCWs; UK.


#Seroprevalence of #Antibodies to #SARS-CoV-2 in 10 Sites in the #USA, March 23-May 12, 2020 (JAMA Intern Med., abstract)

[Source: JAMA Internal Medicine, full page: (LINK). Abstract, edited.]

Seroprevalence of Antibodies to SARS-CoV-2 in 10 Sites in the United States, March 23-May 12, 2020

Fiona P. Havers, MD, MHS1; Carrie Reed, PhD1; Travis Lim, DrPH1; Joel M. Montgomery, PhD1; John D. Klena, PhD1; Aron J. Hall, DVM1; Alicia M. Fry, MD1; Deborah L. Cannon, BS1; Cheng-Feng Chiang, PhD1; Aridth Gibbons, BS1; Inna Krapiunaya, MS1; Maria Morales-Betoulle, PhD1; Katherine Roguski, MPH1; Mohammad Ata Ur Rasheed, PhD1; Brandi Freeman, PhD1; Sandra Lester, PhD1; Lisa Mills, PhD1; Darin S. Carroll, PhD1; S. Michele Owen, PhD1; Jeffrey A. Johnson, PhD1; Vera Semenova, PhD1; Carina Blackmore, DVM2; Debra Blog, MD3; Shua J. Chai, MD4; Angela Dunn, MD5; Julie Hand, MSPH6; Seema Jain, MD7; Scott Lindquist, MD8; Ruth Lynfield, MD9; Scott Pritchard, MPH10; Theresa Sokol, MPH11; Lynn Sosa, MD12; George Turabelidze, MD13; Sharon M. Watkins, PhD14; John Wiesman, DrPH15; Randall W. Williams, MD16; Stephanie Yendell, DVM17; Jarad Schiffer, MS1; Natalie J. Thornburg, PhD1

Author Affiliations: 1 CDC COVID-19 Response Team, Centers for Disease Control and Prevention, Atlanta, Georgia; 2 Florida Department of Health, Tallahassee; 3 New York State Department of Health, Albany; 4 Division of State and Local Readiness, Centers for Disease Control and Prevention, Atlanta, Georgia; 5 Utah Department of Health, Salt Lake City; 6 Louisiana Department of Health, New Orleans; 7 California Department of Health, Richmond; 8 Washington State Department of Health, Tumwater; 9 Minnesota Department of Health, St Paul; 10 Florida Department of Health, Tallahassee; 11 Louisiana Department of Health, New Orleans; 12 Connecticut Department of Public Health, Hartford; 13 Missouri Department of Health and Senior Services, Jefferson City; 14 Pennsylvania Department of Health, Harrisburg; 15 Washington State Department of Health, Tumwater; 16 Missouri Department of Health and Senior Services, Jefferson City; 17 Minnesota Department of Health, St Paul

JAMA Intern Med. Published online July 21, 2020. doi:10.1001/jamainternmed.2020.4130


Key Points

  • Question  – What proportion of persons in 10 US sites had detectable antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from March 23 to May 12, 2020?
  • Findings  – In this cross-sectional study of 16 025 residual clinical specimens, estimates of the proportion of persons with detectable SARS-CoV-2 antibodies ranged from 1.0% in the San Francisco Bay area (collected April 23-27) to 6.9% of persons in New York City (collected March 23-April 1). Six to 24 times more infections were estimated per site with seroprevalence than with coronavirus disease 2019 (COVID-19) case report data.
  • Meaning  – For most sites, it is likely that greater than 10 times more SARS-CoV-2 infections occurred than the number of reported COVID-19 cases; most persons in each site, however, likely had no detectable SARS-CoV-2 antibodies.




Reported cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection likely underestimate the prevalence of infection in affected communities. Large-scale seroprevalence studies provide better estimates of the proportion of the population previously infected.


To estimate prevalence of SARS-CoV-2 antibodies in convenience samples from several geographic sites in the US.

Design, Setting, and Participants  

This cross-sectional study performed serologic testing on a convenience sample of residual sera obtained from persons of all ages. The serum was collected from March 23 through May 12, 2020, for routine clinical testing by 2 commercial laboratory companies. Sites of collection were San Francisco Bay area, California; Connecticut; south Florida; Louisiana; Minneapolis-St Paul-St Cloud metro area, Minnesota; Missouri; New York City metro area, New York; Philadelphia metro area, Pennsylvania; Utah; and western Washington State.


Infection with SARS-CoV-2.

Main Outcomes and Measures  

The presence of antibodies to SARS-CoV-2 spike protein was estimated using an enzyme-linked immunosorbent assay, and estimates were standardized to the site populations by age and sex. Estimates were adjusted for test performance characteristics (96.0% sensitivity and 99.3% specificity). The number of infections in each site was estimated by extrapolating seroprevalence to site populations; estimated infections were compared with the number of reported coronavirus disease 2019 (COVID-19) cases as of last specimen collection date.


Serum samples were tested from 16 025 persons, 8853 (55.2%) of whom were women; 1205 (7.5%) were 18 years or younger and 5845 (36.2%) were 65 years or older. Most specimens from each site had no evidence of antibodies to SARS-CoV-2. Adjusted estimates of the proportion of persons seroreactive to the SARS-CoV-2 spike protein antibodies ranged from 1.0% in the San Francisco Bay area (collected April 23-27) to 6.9% of persons in New York City (collected March 23-April 1). The estimated number of infections ranged from 6 to 24 times the number of reported cases; for 7 sites (Connecticut, Florida, Louisiana, Missouri, New York City metro area, Utah, and western Washington State), an estimated greater than 10 times more SARS-CoV-2 infections occurred than the number of reported cases.

Conclusions and Relevance  

During March to early May 2020, most persons in 10 diverse geographic sites in the US had not been infected with SARS-CoV-2 virus. The estimated number of infections, however, was much greater than the number of reported cases in all sites. The findings may reflect the number of persons who had mild or no illness or who did not seek medical care or undergo testing but who still may have contributed to ongoing virus transmission in the population.

Keywords: SARS-CoV-2; COVID-19; Serology; Seroprevalence; USA.