COVID-19 Antibody Prevalence From July to September 2020: One Army Infantry Brigade's Experience

Lab companies developed serology tests for antibody detection of severe acute respiratory syndrome coronavirus-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, chemiluminescent immunoassay (CLIA), or colloidal gold-based immunochromatographic assay. With the advent of coronavirus disease 2019 (COVID-19), nucleic acid amplification technology (NAAT) SARS-CoV-2 testing for active infection was not widely available to healthy, active-duty Soldiers. The purpose of this surveillance survey was to determine the prevalence of prior SARS-CoV-2 infection and symptoms of COVID-19 within a mechanized infantry brigade.

Active-duty military Servicemembers (= 18 years) from a mechanized infantry brigade provided serum samples for testing for the Elecsys® Anti-SARS-CoV-2 qualitative antibody test from June to September 2020 at Joint Base Lewis McChord (JBLM). In addition, participants filled out a questionnaire for symptoms and exposure to COVID-19 from January to September 2020. The surveillance team collected and analyzed antibody testing results and questionnaires from participants for antibody positivity rates and symptom prevalence.

A total of 264 participants were tested, with one (0.4%) participant testing positive for the SARS-CoV-2 antibody. On the questionnaire, 144 of 264 (54.5%) endorsed symptoms of COVID-19 from January to September 2020. The most common symptoms were headache (35%), rhinorrhea (34%), cough (35%), and sore throat (31%). A total of 31 respondents (12%) had been quarantined as a trace contact to a COVID-19 positive patient.

While there are limitations inherent to SARS-CoV-2 antibody testing and the survey, prevalence of prior SARS-CoV-2 infection is low. In this sample, symptoms for COVID-19 were prevalent with significant days of duty lost. Prevalence of prior SARS-CoV-2 infection in this sample may be generalizable to the larger brigade. Prevalence of symptoms of possible COVID-19 are not generalizable to the larger brigade. There is utility to further studies of SARS-CoV-2 antibody prevalence in military populations for purposes of vaccination triaging and deployment readiness.