Table 1.
Characteristics of Patients with Pertussis Admitted to IMPACT Hospitals in Canada, 1999–2015
| Characteristic | Pertussis Cases | P d | ||
|---|---|---|---|---|
| All (n = 1402)a | Confirmed (n = 1157)b | Probable (n = 245)c | ||
| Demographics | ||||
| Sex, male (n [% of total]) | 655 (46.71) | 525 (45.37) | 130 (53.06) | .0340 |
| Age (median [overall range (IQR)]) (wk) | 10 (1–886 [6–17]) | 9 (1–884 [6–16]) | 11 (1–886 [7–22]) | .0027 |
| Age group (n [% of total]) | ||||
| <1 year | 1265 (90.23) | 1056 (91.27) | 209 (85.30) | |
| 0–1 mo | 612 (43.65) | 523 (45.20) | 89 (36.32) | |
| 2–3 mo | 460 (32.81) | 381 (32.92) | 79 (32.24) | |
| 4–5 mo | 119 (8.48) | 91 (7.86) | 28 (11.42) | |
| 6–11 mo | 74 (5.27) | 61 (5.27) | 13 (5.30) | |
| 1–4 years | 72 (5.14) | 53 (4.58) | 19 (7.75) | |
| 5–9 years | 24 (1.71) | 15 (1.29) | 9 (3.67) | |
| 10–16 years | 41 (2.92) | 33 (2.85) | 8 (3.26) | |
| Clinical features | ||||
| Comorbidity (n [% of total])e | ||||
| Underlying condition(s) | 178 (12.69) | 152 (13.13) | 26 (10.61) | .5002 |
| Prematurityf | 50 (3.56) | 44 (3.80) | 6 (2.44) | |
| Pulmonary | 31 (2.21) | 23 (1.98) | 8 (3.26) | |
| Neurologic | 27 (1.92) | 24 (2.07) | 3 (1.22) | |
| Congenital cardiac | 23 (1.64) | 20 (1.72) | 3 (1.22) | |
| Gastrointestinal | 20 (1.42) | 16 (1.38) | 4 (1.63) | |
| Genetic-metabolic | 13 (0.92) | 10 (0.86) | 3 (1.22) | |
| Failure to thrive | 12 (0.85) | 11 (0.95) | 1 (0.40) | |
| Immunocompromised | 10 (0.71) | 10 (0.86) | 0 (0.00) | |
| Other | 34 (2.42) | 30 (2.59) | 4 (1.63) | |
| Seizures (n [% of total]) | .1204 | |||
| New seizures | 30 (2.13) | 28 (2.42) | 2 (0.81) | |
| Exacerbation of an existing seizure disorder | 8 (0.57) | 8 (0.69) | 0 (0.00) | |
| Encephalopathy (n [% of total]) | 8g (0.57) | 8 (0.69) | 0 (0.00) | .3443 |
| Outcome | ||||
| Hospitalization | ||||
| Median (overall range [IQR]) (days) | 7 (1–185 [3–13]) | 8 (1–185 [4–14]) | 4 (1–45 [2–7]) | <.0001 |
| Age-specific median LOS (overall range [IQR]) (days) | ||||
| <1 year | 8 (1–185 [3–14]) | 9 (1–185 [4–15]) | 4 (1–45 [2–8]) | <.0001 |
| 0–1 mo | 10 (1–87 [5–16]) | 11 (1–87 [6–17]) | 5 (1–45 [2–9]) | <.0001 |
| 2–3 mo | 6 (1–185 [3–12]) | 7 (1–185 [3–12]) | 4 (1–37 [2–9]) | .0003 |
| 4–5 mo | 4 (1–59 [2–8]) | 5 (1–59 [3–9.50]) | 3 (1–15 [2–4]) | .0002 |
| 6–11 mo | 4 (1–38 [2–9.75]) | 4 (1–38 [2–10]) | 3 (1–8 [2–5]) | .0507 |
| 1–4 years | 3 (1–60 [1–5]) | 3 (1–60 [2–5]) | 2 (1–13 [1–4.50]) | .2307 |
| 5–9 years | 2 (1–8 [1–5]) | 2 (1–68 [1–4.5]) | 3 (1–5 [2–5]) | .5019 |
| 10–16 years | 3 (1–14 [1–5]) | 1 (1–14 [2–5]) | 1 (1–5 [1–5]) | .1244 |
| ICU admission (n [% of total]) | 357 (25.46) | 316 (27.31) | 41 (16.73) | .0007 |
| Median ICU LOS (overall range [IQR]) (days) | 4 (1–79 [2–9]) | 5 (1–79 [2–10]) | 3 (1–23 [2–7]) | .0268 |
| Age-specific median ICU LOS (overall range [IQR]) (days) | ||||
| <1 year | 5 (1–79 [2-10]) | 5 (1–79 [2.5-10]) | 3 (1–23 [2–7]) | .0333 |
| 0–1 mo | 5 (1–79 [3–9]) | 5 (1–79 [3-9.75]) | 3 (1–23 [2–6]) | .0314 |
| 2–3 mo | 4 (1–62 [2–10]) | 4 (1–62 [2-9]) | 3 (1–13 [3–11]) | .8883 |
| 4–5 mo | 7 (1–42 [2–12]) | 7 (1–42 [2.50-12.25]) | 7 (1–8 [4–7.50]) | .5595 |
| 6–11 mo | 2.5 (1–16 [1.75–9]) | 5 (1–16 [2.25–13]) | 1.5 (1–2 [1.25–1.75]) | .2377 |
| 1–4 years | 2 (1–29 [1–4]) | 2.5 (1–29 [1.75–5.25]) | 1 (1–1 [1–1]) | .3226 |
| Death (n [% of total]) | 21 (1.49) | 21 (1.81) | 0 (0.00) | .0664 |
Abbreviations: IMPACT, Canadian Immunization Monitoring Program, Active; IQR, interquartile range; LOS, length of stay.
aIncludes confirmed and probable pertussis cases.
bLaboratory-confirmed (n = 1145) or epidemiologically linked (n = 12) pertussis cases.
cClinical pertussis cases.
dFor the comparison of confirmed versus probable pertussis cases.
eAs clinically denoted in the records; patients could have >1 comorbidity.
fPrematurity was defined as birth at <37 weeks’ gestation.
gFive case-patients had both new seizures and encephalopathy.