Figure 1.

Identification of subjects meeting inclusion criteria. A, Duration between the first and subsequent positive SARS-CoV-2 NAAT for all subjects with ≥1 SARS-CoV-2 NAAT collected at the Massachusetts General Hospital ≥1 d after an initial positive SARS-CoV-2 NAAT between March 14 and 30 December 2020. B, Flow chart of subjects included in the study. *Positive SARS-CoV-2 NAAT includes positive/detected and presumptive positive NAAT result interpretations. ^†Initial positive SARS-CoV-2 NAAT includes NAATs performed at an outside facility with results available in the MGH electronic medical record. Abbreviations: Ct, cycle threshold; LRT, lower respiratory tract; MGH, Massachusetts General Hospital; NAAT, nucleic acid amplification test; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; URT, upper respiratory tract.