1. Characteristics of identified studies: population.
| Characteristic | Number of studies | Number of participants (sum) | Number of participants (median, range) | |
| Enrolment period (minimum start, maximum end) | 30 January 2020 to 31 October 2021 | |||
| Missing dates | 79 | |||
| Overall | 318 | 5,061,795 | 317 (100 to 1,277,747) | |
| Age class | ||||
| Adult | 297 | |||
| Paediatric | 10 | |||
| Adult ‐ neonate | 13 | |||
| Include previously SARS‐CoV‐2‐positive participants | 84 | |||
| Report ethnicity in at least the baseline characteristics | 98 | |||
| Population: comorbidities | ||||
| Solid tumours | 47 | 183,974 | 200 (34 to 95,935) | |
| Haematological malignancies | 54 | 46,928 | 149 (14 to 32,156) | |
| Haematological malignancies, stem cell transplant | 22 | 2456 | 108.5 (12 to 397) | |
| Kidney disease | 6 | 41,903 | 50.5 (21 to 41,597) | |
| Dialysis | 48 | 189,142 | 172.5 (26 to 142,826) | |
| Chronic heart disease | 9 | 73,147 | 178 (21 to 70,716) | |
| Liver disease | 7 | 40,796 | 92 (12 to 40,074) | |
| Lung disease | 5 | 2377 | 104 (16 to 1893) | |
| Transplant: kidney | 43 | 12,991 | 148 (19 to 2350) | |
| Transplant: heart | 9 | 540 | 46 (16 to 134) | |
| Transplant: liver | 12 | 843 | 60 (11 to 161) | |
| Transplant: other or mixed | 19 | 56,514 | 187 (5 to 48,213) | |
| HIV/AIDS | 10 | 3508 | 105 (4 to 2103) | |
| Multiple sclerosis | 17 | 6331 | 239 (58 to 912) | |
| Inflammatory bowel disease | 15 | 40,842 | 436 (58 to 14,697) | |
| Rheumatoid arthritis | 5 | 6385 | 189 (129 to 5493) | |
| Systemic lupus erythematosus | 7 | 1761 | 126 (19 to 696) | |
| Psoriasis | 5 | 1452 | 101 (51 to 788) | |
| Rheumatic diseases, mixed | 28 | 55,175 | 393.5 (45 to 35,475) | |
| Other autoimmune diseases | 13 | 8344 | 108 (17 to 6380) | |
| Other | 24 | 161,134 | 287 (24 to 279,145) | |
| Population: healthy | ||||
| Pregnancy | 26 | 360,738 | 1071 (84 to 130,875) | |
| Breastfeeding | 7 | 12,433 | 180 (31 to 6815) | |
| Comparator group | Healthy control | 116 | 3,523,037 | 91.5 (7 to 963,962) |
| Country | ||||
| Multiple countries | 12 | |||
| Austria | 3 | |||
| Belgium | 3 | |||
| Brazil | 3 | |||
| Canada | 7 | |||
| China | 9 | |||
| Denmark | 2 | |||
| France | 28 | |||
| Germany | 10 | |||
| Greece | 7 | |||
| India | 2 | |||
| Iran, Islamic Rep. | 5 | |||
| Israel | 51 | |||
| Italy | 24 | |||
| Kuwait | 2 | |||
| Lithuania | 2 | |||
| Norway | 3 | |||
| Poland | 4 | |||
| Portugal | 4 | |||
| Qatar | 2 | |||
| Spain | 10 | |||
| Switzerland | 2 | |||
| United Kingdom | 31 | |||
| United States | 81 | |||
| Other* | 11 | |||
| Abbreviations: SARS‐CoV‐2: severe acute respiratory syndrome coronavirus 2 | ||||
*1 study each: Argentina, Australia, Japan, Mexico, the Netherlands, Peru, Russian Federation, Saudi Arabia, South Africa, Sweden, United Arab Emirates.