Study characteristics
| Study | Design | Country | Population size | Age (years) | Sex (% female) | COVID-19 confirmation method | Follow-up time (days) | Follow-up timepoint | Follow-up mode |
| Non-hospitalised | |||||||||
| Hopkins et al58 | Cross sectional | UK | 434 | Median (range): 40 (19–77) | 75 | PCR or serological assays (26.3%) | 6 months | First survey | Electronic survey |
| Klein et al47 | Cohort (P) | Israel | 103 | Mean (SD): 35 (12) | 38 | PCR (RT-PCR) | 6 months | Onset | Phone interview |
| Petersen et al32 | Cohort (P) | Faroe Islands | 180 | Mean (SD; range): 39.9 (19.4; 0–93) | 54 | PCR (RT-PCR) | Mean (SD) 125 (17) | Onset | Phone interview |
| Stavem et al68 | Crosssectional | Norway | 451 | Mean (SD): 49.8 (15.2) | 56 | PCR (RT-PCR) | Median (range): 117 (41–193) | Onset | Outpatient visit and survey |
| Non-hospitalised and hospitalised | |||||||||
| Parente-Arias et al55 | Cohort (P) | Spain | 151 | Mean (range): 55.2 (18–88) | 65 | PCR (RT-PCR) | Mean (SD): 100.5 (3.3) | Admission | Phone interview |
| Venturelli et al60 | Cohort (P) | Italy | 767 | Mean (SD): 63 (13.6) | 33 | PCR (RT-PCR) (94%); serology (5%) Clinician diagnosis (1.2%) | Median (IQR): 105 (84–127) | Onset | Outpatient visit |
| Anastasio et al41 | Cohort (P) | Italy | 379 | Median (IQR; range): 56 (49–63; 20–80) | 54 | PCR (RT-PCR) | Median (IQR): 135 (102–175) | Onset | Outpatient visit |
| Einvik et al67 | Crosssectional | Norway | 538 | Mean (SD) 57.7 (14.2) (hospital) 49.6 (15.3) | 42 (hospital) 56 | PCR (RT-PCR) | Mean (SD): 112 (30) (hospital) 118 (27) | Onset | Outpatient visit and survey |
| Jacobson et al40 | Cohort (P) | USA | 118 | Mean (SD): 43.3 (14.4) | 47 | PCR (RT-PCR) | Mean (SD): 119.3 (33) | Diagnosis | Outpatient visit |
| Logue et al35 | Cohort (P) | USA | 177 21 (C) | Mean (SD): 48 (15.2) | 57 | Lab confirmed | Median (range): 169 (31–300) | Onset | Electronic survey |
| Mazza et al70 | Cohort (P) | Italy | 226 | Mean (SD; range): 58 (12.8; 26–87) | 34 | PCR (RT-PCR) | Mean (SD): 90 (13.4) | Discharge | Phone interview |
| Rass et al50 | Cohort (P) | Austria | 135 | Median (IQR; range) 56 (48–68; 19–87) | 39 | PCR (RT-PCR) | Median (IQR): 102 (91–110) | Onset | Outpatient visit |
| Sonnweber et al48 | Cohort (P) | Austria | 145 | Mean (SD): 57 (14) | 43 | PCR (RT-PCR) | Mean (SD): 103 (21) | Diagnosis | Outpatient visit |
| Hospitalised | |||||||||
| Alharthy et al54 | Cohort (P) | Saudi Arabia | 127 | Mean (SD): 47 (11.38) | 21 | PCR (RT-PCR) | 4 months | Discharge | Outpatient visit |
| Arnold et al37 | Cohort (P) | UK | 110 | Median (IQR): 60 (46–73) | 38 | PCR or radiological diagnosis | Median (IQR): 90 (80–97) | Onset | Outpatient visit |
| Baricich et al63 | Crosssectional | Italy | 204 | Mean (SD): 57.9 (12.8) | 40 | NR | Mean (SD): 124.7 (17.5) | Discharge | Outpatient visit |
| Bellan et al42 | Cohort (P) | Italy | 238 | Median (IQR): 61 (50–71) | 40 | PCR (RT-PCR) (97.5%); bronchoalveolar lavage (0.4%); serology/radiological (2.1%) | 3–4 months | Discharge | Outpatient visit |
| Blanco et al38 | Cohort (P) | Spain | 100 | Mean (SD) TLco<80: 54.98 (10.72) TLco>80: 54.75 (9.83) | 36 | PCR (RT-PCR) | Median (IQR): 104 (89.25–126.75) | Onset | Outpatient visit |
| Doyle et al66 | Cohort (P) | UK | 129 | Mean: 62 (Cambridge) 56 (London) | 31 (Cambridge) 27 (London) | PCR (RT-PCR) | Median (range): 113 (96–138) | Discharge | NR |
| Garrigues et al65 | Cohort (P) | France | 120 | Mean (SD): 63.2 (15.7) | 38 | PCR (RT-PCR) | Mean (SD): 110.9 (11.1) | Admission | Phone interview |
| Gherlone et al57 | Cohort (P and R) | Italy | 122 | Median (IQR): 62.5 (53.9–74.1) | 25 | PCR (RT-PCR) | Median (IQR): 104 (95–132) | Discharge | Outpatient visit |
| Han et al46 | Cohort (P) | China | 114 | Mean (SD; range): 54 (12; 24–82) | 30 | PCR (RT-PCR) | Mean (SD): 175 (20) | Onset | Outpatient visit |
| Huang et al56 | Cohort (P and R) | China | 1733 | Median (IQR): 57 (47–65) | 48 | Lab confirmed | Median (IQR): 186 (175–199) | Onset | Outpatient visit |
| Zhang et al31 | Cohort (R/S) | China | 527 | Median (IQR; range): 42.5 (32–54; 0–91) | 44 | NR | 6 months | Discharge | Outpatient visit |
| Lerum et al61 | Cohort (P) | Norway | 103 | Median (25th–75th percentile): 59 (49–72) | 48 | Nasopharyngeal swab | 3 months | Discharge | Outpatient visit |
| Méndez et al49 | Cohort (R/S) | Spain | 215 | Median (IQR): 55 (47–66) | 40 | Lab confirmed | Median (IQR): 87 (62–109) | Discharge | Outpatient visit |
| Nguyen et al33 | Cohort (P) | France | 125 | Median (IQR; range): 36 (27–48; 16–85) | 55 | PCR (RT-PCR) | Mean (SD): 221.7 (10.9) | Onset | Phone interview |
| Nugent et al36 | Cohort (R/S) | USA | 182 1430 (C) | Median (IQR): 67.4 (58.3–80.1) | 47 | PCR (RT-PCR) | Median (IQR): 92.9 (52.5–127.7) | Discharge | Outpatient visit |
| Qin et al53 | Cohort (P) | China | 647 | Mean (SD): 58 (15) | 56 | PCR (RT-PCR) | 90 | Discharge | Outpatient visit |
| Qu et al34 | Cohort (P) | China | 540 | Median (IQR): 47.50 (37–57) | 50 | PCR (RT-PCR) | 3 months | Discharge | Electronic survey |
| Sibila et al51 | Cohort (P) | Spain | 172 | Mean (SD): 56.1 (19.8) | 43 | NR | Mean (SD): 101.5 (19.9) | Discharge | Outpatient visit |
| Simani et al59 | Cohort (P) | Iran | 120 | Mean (SD): 54.62 (16.94) | 33 | PCR or radiological diagnosis | 6 months | Discharge | Outpatient visit |
| Suárez-Robles et al64 | Crosssectional | Spain | 134 | Mean (SD): 58.53 (18.53) | 54 | PCR (RT-PCR) | 90 | Discharge | Phone survey |
| Sykes et al39 | Cohort (P) | UK | 134 | Median (range): 58 (25–89) | 34 | PCR (RT-PCR) | Median (range): 113 (46–167) | Discharge | Outpatient visit |
| Taboada et al62 | Cross sectional | Spain | 183 | Mean (SD): 65.9 (14.1) | 40 | PCR (RT-PCR) | 6 months | Discharge | Unstructured interview |
| Weng et al45 | Cohort (P) | China | 117 | 45.3%≥60 years | 44 | Viral nucleic acid test | 90 | Discharge | Phone interview |
| Xiong et al44 | Cohort (P) | China | 538 184 (C) | Median (IQR; range): 52 (41–62; 22–79) | 55 | PCR (RT-PCR) | Median (IQR; range): 97.0 (95.0–102.0; 91–116) | Discharge | Phone interview |
| Xu et al43 | Case–control | China | 103 27 (C) | Median (IQR) M/M: 56 (45–63) S/C: 61 (55–68) | M/M: 58.8 S/C: 53.6 | NR | 3 months | Discharge | Outpatient visit |
| Zhang et al52 | Cohort (P) | China | 310 | Median (IQR): 51 (31.8–61) | 50 | PCR (RT-PCR) | Median (IQR): 92.0 (90–100) | Discharge | Outpatient visit |
C, control group; M/M, mild/moderate; NR, not reported; P, prospective; PCR, polymerase chain reaction; R, retrospective; RT, Reverse transcription; S/C, severe/critical; TLco, carbon monoxide transfer factor.