Rates of Asymptomatic COVID-19 Infection and Associated Factors in Olmsted County, Minnesota, in the Prevaccination Era

Celine M Vachon; Aaron D Norman; Kavita Prasad; Dan Jensen; Gavin M Schaeferle; Kristy L Vierling; Meaghan Sherden; Michelle R Majerus; Katherine A Bews; Ethan P Heinzen; Amy Hebl; Kathleen J Yost; Richard B Kennedy; Elitza S Theel; Aditya Ghosh; Meghan Fries; Chung-Il Wi; Young J Juhn; Priya Sampathkumar; William G Morice 2nd; Walter A Rocca; Aaron J Tande; James R Cerhan; Andrew H Limper; Henry H Ting; Gianrico Farrugia; Rickey E Carter; Lila J Finney Rutten; Robert M Jacobson; Jennifer St Sauver

doi:10.1016/j.mayocpiqo.2022.10.001

Rates of Asymptomatic COVID-19 Infection and Associated Factors in Olmsted County, Minnesota, in the Prevaccination Era

Mayo Clin Proc Innov Qual Outcomes. 2022 Dec;6(6):605-617. doi: 10.1016/j.mayocpiqo.2022.10.001. Epub 2022 Oct 18.

Authors

Celine M Vachon¹, Aaron D Norman¹, Kavita Prasad², Dan Jensen³, Gavin M Schaeferle⁴, Kristy L Vierling⁴, Meaghan Sherden⁵, Michelle R Majerus⁶, Katherine A Bews⁴, Ethan P Heinzen⁴, Amy Hebl⁷, Kathleen J Yost¹, Richard B Kennedy⁸, Elitza S Theel⁹, Aditya Ghosh¹⁰, Meghan Fries¹¹, Chung-Il Wi¹², Young J Juhn¹³, Priya Sampathkumar¹⁴, William G Morice 2nd¹⁵, Walter A Rocca^{1

16}, Aaron J Tande¹⁷, James R Cerhan¹, Andrew H Limper¹⁸, Henry H Ting¹⁹, Gianrico Farrugia²⁰, Rickey E Carter²¹, Lila J Finney Rutten¹, Robert M Jacobson^{1

13}, Jennifer St Sauver¹

Affiliations

¹ Department of Quantitative Health Sciences, Mayo Clinic, Rochester, MN.
² Integrative Medicine, Zumbro Valley Health Center, Mayo Clinic, Rochester, MN.
³ Department of Health, Housing and Human Services Administration, Olmsted County Public Health, Mayo Clinic, Rochester, MN.
⁴ Robert D. and Patricia E. Kern Center for the Science of Health Care Delivery, Mayo Clinic, Rochester, MN.
⁵ Department of Epidemiology, Surveillance and Preparedness Team, Olmsted County Public Health, Mayo Clinic, Rochester, MN.
⁶ Administration, Hutchinson Health, Hutchinson, MN.
⁷ Department of Human Resources, Olmsted County, Mayo Clinic, Rochester, MN.
⁸ Vaccine Research Group, Division of General Internal Medicine, Mayo Clinic, Rochester, MN.
⁹ Department of Laboratory Medicine and Pathology, Division of Clinical Microbiology, Mayo Clinic, Rochester, MN.
¹⁰ Department of Internal Medicine, Northeast Georgia Medical Center, Gainesville, GA.
¹¹ University of Notre Dame, South Bend, IA.
¹² Department of Precision Population Science Lab, Mayo Clinic, Rochester, MN.
¹³ Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN.
¹⁴ Division of Infectious Diseases, Department of Medicine, Mayo Clinic, Rochester, MN.
¹⁵ Department of Laboratory Medicine & Pathology, Mayo Clinic, Rochester, MN.
¹⁶ Department of Neurology and Women's Health Research Center, Mayo Clinic, Rochester, MN.
¹⁷ Division of Public Health, Infectious Diseases, and Occupational Medicine, Mayo Clinic, Rochester, MN.
¹⁸ Department of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, MN.
¹⁹ Department of Cardiology, Emory University, Atlanta, GA.
²⁰ Division of Gastroenterology & Hepatology, Department of Medicine, Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN.
²¹ Department of Quantitative Health Sciences, Mayo Clinic, Jacksonville, FL.

Abstract

Objective: To estimate rates and identify factors associated with asymptomatic COVID-19 in the population of Olmsted County during the prevaccination era.

Patients and methods: We screened first responders (n=191) and Olmsted County employees (n=564) for antibodies to SARS-CoV-2 from November 1, 2020 to February 28, 2021 to estimate seroprevalence and asymptomatic infection. Second, we retrieved all polymerase chain reaction (PCR)-confirmed COVID-19 diagnoses in Olmsted County from March 2020 through January 2021, abstracted symptom information, estimated rates of asymptomatic infection and examined related factors.

Results: Twenty (10.5%; 95% CI, 6.9%-15.6%) first responders and 38 (6.7%; 95% CI, 5.0%-9.1%) county employees had positive antibodies; an additional 5 (2.6%) and 10 (1.8%) had prior positive PCR tests per self-report or medical record, but no antibodies detected. Of persons with symptom information, 4 of 20 (20%; 95% CI, 3.0%-37.0%) first responders and 10 of 39 (26%; 95% CI, 12.6%-40.0%) county employees were asymptomatic. Of 6020 positive PCR tests in Olmsted County with symptom information between March 1, 2020, and January 31, 2021, 6% (n=385; 95% CI, 5.8%-7.1%) were asymptomatic. Factors associated with asymptomatic disease included age (0-18 years [odds ratio {OR}, 2.3; 95% CI, 1.7-3.1] and >65 years [OR, 1.40; 95% CI, 1.0-2.0] compared with ages 19-44 years), body mass index (overweight [OR, 0.58; 95% CI, 0.44-0.77] or obese [OR, 0.48; 95% CI, 0.57-0.62] compared with normal or underweight) and tests after November 20, 2020 ([OR, 1.35; 95% CI, 1.13-1.71] compared with prior dates).

Conclusion: Asymptomatic rates in Olmsted County before COVID-19 vaccine rollout ranged from 6% to 25%, and younger age, normal weight, and later tests dates were associated with asymptomatic infection.

Keywords: BMI, body mass index; HOUSES, HOUsing-based SocioEconomic Status; OR, odds ratio; PCR, polymerase chain reaction; REP, Rochester Epidemiology Project; RT-PCR, reverse transcriptase-polymerase chain reaction; SES, socioeconomic status.

Abstract

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