Page 62 - JSOM Fall 2021

COVID-19 Antibody Prevalence From July to September 2020

One Army Infantry Brigade’s Experience

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Alex Y. Koo, MD *; David K. Rodgers, PA-C ;
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Keaton A. Johnson, PA-C ; Leanna L. Gordon, DO, MPH ;
Luke E. Mease, MD ; Kyle S. Couperus, MD 6
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ABSTRACT
Objectives: Lab companies developed serology tests for anti- Keywords: COVID-19; SARS-CoV-2; antibody; Army Infantry Bri-
body detection of severe acute respiratory syndrome corona- gade; vaccine; vaccination; prevalence
virus-2 (SARS-CoV-2) with United States Food and Drug
Administration (FDA) emergency use authorization. Antibody
detection uses purified proteins of SARS-CoV-2 to determine
antibody binding via enzyme-linked immunosorbent assay, che- Introduction
miluminescent immunoassay (CLIA), or colloidal gold-based The severe acute respiratory syndrome coronavirus-2 (SARS-
immunochromatographic assay. With the advent of coronavi- CoV-2) is a single-stranded ribonucleic acid (RNA) virus that
rus disease 2019 (COVID-19), nucleic acid amplification tech- causes the coronavirus disease 2019 (COVID-19). Its spike (S)
nology (NAAT) SARS-CoV-2 testing for active infection was protein accounts for its high infectivity, while the nucleocap-
not widely available to healthy, active-duty Soldiers. The pur- sid (N) protein contributes to RNA replication. The receptor
pose of this surveillance survey was to determine the prevalence binding domain in the S protein enhances its affinity for the
of prior SARS-CoV-2 infection and symptoms of COVID-19 human angiotensin-converting enzyme 2 (hACE2) receptors,
within a mechanized infantry brigade. Materials and Methods: found within the lungs, kidneys, and heart. 1
Active-duty military Servicemembers (≥ 18 years) from a mech-
anized infantry brigade provided serum samples for testing for Currently, testing for SARS-CoV-2 is primarily done through
the Elecsys Anti-SARS-CoV-2 qualitative antibody test from nucleic acid amplification tests (NAAT), a class of tests in-
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June to September 2020 at Joint Base Lewis McChord (JBLM). cluding reverse transcriptase–polymerase chain reaction (RT-
In addition, participants filled out a questionnaire for symp- PCR). The RT-PCR identifies and amplifies the SARS-CoV-2
toms and exposure to COVID-19 from January to September RNA, but clinical sensitivities with PCR can be as low as 75%,
2020. The surveillance team collected and analyzed antibody dependent on assay type and timing of testing. The RT-PCR
testing results and questionnaires from participants for anti- remains with high specificities from 98% to 100%. 2
body positivity rates and symptom prevalence. Results: A total
of 264 participants were tested, with one (0.4%) participant Serology testing was developed to detect antibodies to the
testing positive for the SARS-CoV-2 antibody. On the question- SARS-CoV-2 virus (anti-SARS-CoV-2). Antibody detection
naire, 144 of 264 (54.5%) endorsed symptoms of COVID-19 uses purified proteins of SARS-CoV-2 to determine antibody
from January to September 2020. The most common symp- binding via enzyme-linked immunosorbent assay, chemilumi-
toms were headache (35%), rhinorrhea (34%), cough (35%), nescent immunoassay (CLIA), or colloidal gold–based immu-
and sore throat (31%). A total of 31 respondents (12%) had nochromatographic assay. The two main antigenic targets are
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been quarantined as a trace contact to a COVID-19 positive the nucleocapsid and spike proteins. IgM and IgA antibodies
patient. Conclusions: While there are limitations inherent to to SARS-CoV-2 can be detected as early as 5 days after symp-
SARS-CoV-2 antibody testing and the survey, prevalence of tom development and are increasingly detected in the second
prior SARS-CoV-2 infection is low. In this sample, symptoms and third weeks. IgG antibodies become detectable between
for COVID-19 were prevalent with significant days of duty 7 and 14 days. While there has been demonstrated cross-
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lost. Prevalence of prior SARS-CoV-2 infection in this sample reactivity with SARS-CoV, Middle East respiratory syndrome
may be generalizable to the larger brigade. Prevalence of symp- coronavirus (MERS-CoV) and other coronavirus types, speci-
toms of possible COVID-19 are not generalizable to the larger ficity of antibody testing is high for SARS-CoV-2 antibodies. 8
brigade. There is utility to further studies of SARS-CoV-2 anti-
body prevalence in military populations for purposes of vacci- With the advent of COVID-19, NAAT SARS-CoV-2 test-
nation triaging and deployment readiness. ing for active infection was not widely available to healthy,
*Correspondence to koo.alex@gmail.com
1 MAJ Alex Y. Koo is in the Medical Corps and affiliated with the Department of Emergency Medicine, Madigan Army Medical Center and the
Okubo Clinic on Joint Base Lewis-McChord, WA. CPT David K. Rodgers and CPT Keaton A. Johnson are affiliated with the Okubo Clinic
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on Joint Base Lewis-McChord. MAJ Leanna L. Gordon and LTC Luke E. Mease are in the Medical Corps and affiliated with the Department
of Preventive Medicine, Madigan Army Medical Center on Joint Base Lewis-McChord. MAJ Kyle S. Couperus is in the Medical Corps and
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affiliated with the Department of Emergency Medicine, Madigan Army Medical Center on Joint Base Lewis-McChord.
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