| Medical history | n (%) | 95% CI |
|---|---|---|
| Pregnancy (current) | 2a(1.3) | 0 to 3 |
| Cancer | 6 (3.9) | 1 to 7 |
| Diabetes | 12 (7.8) | 3.5 to 12 |
| HIV or other immune-deficiency diseases | 0 | n/a |
| Heart disease | 10 (6.5) | 2.5 to 10.4 |
| Asthma (requiring medication) | 13 (8.5) | 4 to 12.9 |
| Chronic lung disease (non-asthma) | 3 (2) | 0 to 4.2 |
| Chronic liver disease | 0 | n/a |
| Chronic haematological disorder | 2 (1.3) | 0 to 3 |
| Chronic kidney disease | 1 (0.7) | 0 to 2 |
| Chronic neurological impairment or disease | 5 (3.3) | 0 to 6.1 |
| Organ or bone marrow recipient | 1 (0.7) | 0 to 2 |
| Other pre-existing condition(s) | 100 (65.4) | 57.8 to 72.9 |
↵a Both second trimester.