Estimated SARS-CoV-2 Seroprevalence in the US as of September 2020 | Infectious Diseases | JAMA Internal Medicine | JAMA Network
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    1 Comment for this article
    SARS-CoV-2 Seroprevalence in the US comments.
    Gary Ordog, MD, DABMT, DABEM | County of Los Angeles, Department of Health Services, Physician Specialist (ret.)
    Thank you for the interesting study. Although your subject numbers seem large, I believe they represent less than one percent of the population, which makes the sample size small. Also, the method of using convenience blood, we really have no idea why these subjects were getting their blood drawn, but we do know it was not for the purpose of the study. That means that the small sample size may be skewed unknowingly and severely towards some unknown confounding variable, for example, perhaps most of them thought they had had COVID-19. So, the validity of drawing conclusions based upon these results is very low, and even trying to make valid conclusions about time trends is questionable because of the possibility of unknown changing confounding variables during that time. That said, I would like to comment on the implications of your study results, even though what I am concluding cannot be valid, just interesting. Most importantly, possibly only 10% of the population have been infected with SARS-CoV-2. That means that possibly, 90% of the population may be still prone to suffer from infection in the pandemic. Without a vaccination, the US could be facing a disaster. Fortunately, it looks like several vaccines are effective, and many more are in the works. If anything, it looks like your study shows that the vaccination program and its success is more important that ever. Thank you, and stay safe until then.
    Original Investigation
    November 24, 2020

    Estimated SARS-CoV-2 Seroprevalence in the US as of September 2020

    Author Affiliations
    • 1COVID-19 Response, US Centers for Disease Control and Prevention, Atlanta, Georgia
    • 2ICF Inc, Fairfax, Virginia
    • 3Quest Diagnostics, Secaucus, New Jersey
    • 4BioReference Laboratories, Elmwood Park, New Jersey
    JAMA Intern Med. Published online November 24, 2020. doi:10.1001/jamainternmed.2020.7976
    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.


    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.