Determinants and Dynamics of SARS-CoV-2 Infection in a Diverse Population: 6-Month Evaluation of a Prospective Cohort Study

J Infect Dis. 2021 Oct 28;224(8):1345-1356. doi: 10.1093/infdis/jiab411.


Background: We studied risk factors, antibodies, and symptoms of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in a diverse, ambulatory population.

Methods: A prospective cohort (n = 831) previously undiagnosed with SARS-CoV-2 infection underwent serial testing (SARS-CoV-2 polymerase chain reaction, immunoglobulin G [IgG]) for 6 months.

Results: Ninety-three participants (11.2%) tested SARS-CoV-2-positive: 14 (15.1%) asymptomatic, 24 (25.8%) severely symptomatic. Healthcare workers (n = 548) were more likely to become infected (14.2% vs 5.3%; adjusted odds ratio, 2.1; 95% confidence interval, 1.4-3.3) and severely symptomatic (29.5% vs 6.7%). IgG antibodies were detected after 79% of asymptomatic infections, 89% with mild-moderate symptoms, and 96% with severe symptoms. IgG trajectories after asymptomatic infections (slow increases) differed from symptomatic infections (early peaks within 2 months). Most participants (92%) had persistent IgG responses (median 171 days). In multivariable models, IgG titers were positively associated with symptom severity, certain comorbidities, and hospital work. Dyspnea and neurologic changes (including altered smell/taste) lasted ≥ 120 days in ≥ 10% of affected participants. Prolonged symptoms (frequently more severe) corresponded to higher antibody levels.

Conclusions: In a prospective, ethnically diverse cohort, symptom severity correlated with the magnitude and trajectory of IgG production. Symptoms frequently persisted for many months after infection.Clinical Trials Registration. NCT04336215.

Keywords: COVID-19; SARS-CoV-2 infection; humoral immunity; longitudinal data analysis; postacute sequelae of COVID-19; prospective cohort; risk factors; symptoms.

Publication types

  • Observational Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Antibodies, Viral / blood*
  • Antibodies, Viral / immunology
  • Asymptomatic Infections / epidemiology
  • COVID-19 / blood
  • COVID-19 / diagnosis*
  • COVID-19 / epidemiology
  • COVID-19 / transmission
  • Comorbidity
  • Female
  • Humans
  • Immunoglobulin G / blood*
  • Immunoglobulin G / immunology
  • Incidence
  • Male
  • Middle Aged
  • Prospective Studies
  • Risk Factors
  • SARS-CoV-2 / immunology
  • SARS-CoV-2 / isolation & purification*
  • Severity of Illness Index*
  • Young Adult


  • Antibodies, Viral
  • Immunoglobulin G

Associated data