Table 3 Demographic characteristics of children recruited to the study. This table includes all children who contributed at least one sample to any analysis. P-values were calculated by Wilcoxon rank-sum test for continuous data, and Pearson’s χ2 test for categorical data (unless any values were less than 5, then Fisher’s exact test was used)
|  | Case (n = 93) | Control (n = 103) | Missing data | p-value |
|---|---|---|---|---|
Age | Median 1.9 years (IQR 1.3–2.8 years) | Median 1.6 years (IQR 1.5–3.2 years) | 0 | 0.91 |
Sex | 58 male (62.4%) | 53 male (51.5%) | 0 | 0.12 |
35 female (37.6%) | 50 female (48.5%) | |||
Aboriginal or Torres strait islander | 2 (2.15%) | 1 (0.97%) | 0 | – |
Seasona | Summer: 7 (7.5%) | Summer: 4 (3.9%) | 0 | 0.39 |
Autumn: 20 (21.5%) | Autumn: 16 (15.5%) | |||
Winter: 45 (48.4%) | Winter: 53 (51.5%) | |||
Spring: 21 (22.6%) | Spring: 30 (29.1%) | |||
Breastfeedingb | ||||
Ever breastfed (yes/no) | 83 (89.2%) | 98 (95.1%) | 1 case (1.1%) | 0.15 |
Duration of breastfeeding | Median 5 months (IQR 1.6–10 months) | Median 10.3 months (IQR 6–13 months) | 1 control (1.0%) | 6.4 × 10−5 |
 Currently breastfeeding | 7 (7.5%) | 14 (13.6%) | 0.17 | |
 over 12 months | 10 (10.8%) | 23 (22.3%) | 0.00077 | |
 6–12 months | 31 (33.3%) | 45 (43.7%) | ||
  < 6 months (excluding never) | 35 (37.6%) | 16 (15.5%) | ||
 never | 9 (9.7%) | 4 (3.9%) | ||
Day care or school attendance | ||||
Currently attending | 74 (79.6%) | 80 (77.7%) | 1 control (1.0%) | – |
Days of day care or school per week | Median 2.5 days (IQR 2–3 days) | Median 2 days (IQR 1.75–3 days) | 0.096 | |
 no day care or school | 19 (20.4%) | 22 (21.4%) | 0.43 | |
  < 2 days/week | 13 (14.0%) | 20 (19.4%) | ||
 2–3 days/week | 52 (55.9%) | 46 (44.7%) | ||
  > 3 days/week | 9 (9.7%) | 14 (13.6%) | ||
Age at day care/school startc | Median 13.5 months (IQR 10 months – 1.9 years) | Median 12 months (IQR 10 months – 1.5 years) | 34 controls (33%) | 0.94 |
Siblings of 5 years of age or younger | 46 (49.5%) | 70 (68.0%) | 1 case (1.1%) | – |
Smoker in the household | 15 (16.1%) | 8 (7.77%) | 0 | 0.069 |
Antibiotic usage in the past month | 61 (65.6%) | 11 (10.7%) | 1 case (1.1%) | 1.9 × 10−15 |
2 controls (1.9%) | ||||
Any chronic illnessd | 18 (19.4%) | 10 (9.71%) | 14 cases (15.1%) | 0.026 |
7 controls (6.8%) | ||||
Ever admitted to hospital for infection | 17 (18.3%) | 11 (10.7%) | 0 | 0.13 |