Table 2. Characteristics of fully vaccinated, partially vaccinated, and unvaccinated hospitalized children.
| Characteristic | Fully vaccinated (n = 595) | Partially vaccinated (n = 556) | Unvaccinated (n = 8,831) | p-value |
|---|---|---|---|---|
| Influenza season | <.001 | |||
| 2010–11 | 122 (20.5%) | 131 (23.6%) | 2,284 (25.9%) | |
| 2011–12 | 102 (17.1%) | 87 (15.6%) | 1,364 (15.4%) | |
| 2012–13 | 169 (28.4%) | 147 (26.4%) | 2,724 (30.8%) | |
| 2013–14 | 202 (33.9%) | 191 (34.4%) | 2,459 (27.8%) | |
| Age (months), Median (IQR) | 25 (16–40) | 17 (12–26) | 20 (12–33) | <.001 |
| Age group | <.001 | |||
| 6–23 months | 279 (46.9%) | 402 (72.3%) | 5,358 (60.7%) | |
| 24–59 months | 316 (53.1%) | 154 (27.7%) | 3,473 (39.3%) | |
| Male sex | 345 (58.0%) | 319 (57.4%) | 5,061 (57.3%) | 0.95 |
| Rural residence | 30 (5.0%) | 38 (6.8%) | 875 (9.9%) | <.001 |
| Neighbourhood income quintile | ||||
| 1 (lowest) | 118 (19.8%) | 110 (19.8%) | 2,140 (24.2%) | <.001 |
| 2 | 105 (17.6%) | 113 (20.3%) | 1,840 (20.8%) | |
| 3 | 126 (21.2%) | 105 (18.9%) | 1,763 (20.0%) | |
| 4 | 132 (22.2%) | 116 (20.9%) | 1,741 (19.7%) | |
| 5 (highest) | 114 (19.2%) | 111 (20.0%) | 1,276 (14.4%) | |
| No. of outpatient visits in past year, Mean ± SD | 14.44 ± 9.47 | 15.32 ± 11.25 | 10.29 ± 8.47 | <.001 |
| No. of hospitalizations in past year, Mean ± SD | 0.88 ± 1.59 | 1.06 ± 1.98 | 0.76 ± 1.43 | <.001 |
| Continuity of care, Mean ± SD | 61.34 ± 26.80 | 60.80 ± 27.28 | 62.53 ± 28.01 | 0.24 |
| Risk factors for influenza complications | ||||
| Any complex chronic condition | 247 (41.5%) | 193 (34.7%) | 2,149 (24.3%) | <.001 |
| Cancer | 9 (1.5%) | 13 (2.3%) | 199 (2.3%) | 0.48 |
| Diabetes | 6 (1.0%) | ≤5 (≤1.0%) | 28 (0.3%) | 0.03 |
| Asthma | 268 (45.0%) | 223 (40.1%) | 3,181 (36.0%) | <.001 |
| Preterm birth | 140 (23.5%) | 112 (20.1%) | 1,385 (15.7%) | <.001 |
| Low birthweight | 135 (22.7%) | 102 (18.3%) | 1,195 (13.5%) | <.001 |
| Month of influenza testa | <.001 | |||
| 2 months before | ≤5 (≤0.8%)b | ≤5 (≤0.9%) | 43 (0.5%) | |
| 1 month before | 51 (8.6%) | 54 (9.7%) | 1,022 (11.6%) | |
| Peak | 99 (16.6%) | 133 (23.9%) | 2,013 (22.8%) | |
| 1 month after | 109 (18.3%) | 112 (20.1%) | 1,900 (21.5%) | |
| 2 months after | 132 (22.2%) | 114 (20.5%) | 1,586 (18.0%) | |
| 3 months after | 106 (17.8%) | 79 (14.2%) | 1,269 (14.4%) | |
| 4 months after | 69 (11.6%) | 41 (7.4%) | 713 (8.1%) | |
| 5 months after | ≤30 (≤5.0%) | ≤20 (≤3.6%) | 285 (3.2%) |
aTime relative to peak month of influenza circulation.
bSome cells suppressed because of small cell size (direct or by inference), which cannot be reported as per privacy regulations.
IQR, interquartile range; SD, standard deviation.