Table 5.
Risk Factors for Admission to ICU and Death in Patients With Pertussis (n = 1392)
| Variable (N) | Univariate Analysis | Multivariable Analysisa | ||
|---|---|---|---|---|
| P | OR (95% CI) | P | aOR (95% CI) | |
| Risk factors for admission to intensive care unit | ||||
| Age | ||||
| ≥16 wk (380) | <.0001 | Reference | <.0001 | Reference |
| <16 wk (1012) | 4.47 (3.12–6.59) | 4.83 (3.30–7.27) | ||
| Sex | ||||
| Male (648) | .569 | Reference | Not included | |
| Female (744) | 0.93 (0.3–1.18) | |||
| Seizures | ||||
| No new seizures (1363) | .0004 | Reference | Not included | |
| New seizures (29) | 3.77 (1.80–8.06) | |||
| Encephalopathy | ||||
| No (1385) | .0074 | Reference | .0073 | Reference |
| Yes (7) | 18.08 (3.07–342.22) | 21.13 (3.18–425.21) | ||
| Prematurityb | ||||
| No (1343) | <.0001 | Reference | <.0001 | Reference |
| Yes (49) | 4.59 (2.58–8.35) | 5.81 (3.04–11.37) | ||
| Comorbidity (other than prematurity) | ||||
| No (1252) | .58 | Reference | Not included | |
| Yes (140) | 1.11 (0.75–1.64) | |||
| Evidence for diagnosis | ||||
| Probable (245) | .0008 | Reference | .0405 | Reference |
| Confirmed (1147) | 1.84 (1.29–2.67) | 1.51 (1.03-2.27) | ||
| Admission date (year) | <.0001 | 1.05 (1.03-1.08) | .0005 | 1.05 (1.02–1.07) |
| Vaccination status (3–4 mo) (n = 184)c | ||||
| Unvaccinated (102) | .665 | Reference | Not included | |
| Age-appropriately vaccinated (n = 82) | 0.83 (0.35-1.89) | |||
| Risk factors for death | ||||
| Age | ||||
| ≥4 wk (1280) | <.0001 | Reference | .0002 | Reference |
| <4 wk (112) | 7.04 (2.57–17.89) | 6.73 (2.39-17.88) | ||
| Sex | ||||
| Male (648) | .0341 | Reference | .0318 | Reference |
| Female (744) | 3.31 (1.19-11.66) | 3.46 (1.21-12.47) | ||
| Prematurity b | ||||
| No (1343) | .0090 | Reference | .0147 | Reference |
| Yes (49) | 5.40 (1.23–16.95) | 5.36 (1.15–18.61) | ||
| Comorbidity other than prematurity | ||||
| No (1252) | .493 | Reference | Not included | |
| Yes (140) | 0.49 (0.03–2.41) | |||
| Admission date (year) | .0217 | 1.11 (1.01–1.22) | .0143 | 1.13 (1.03–1.25) |
Abbreviations: aOR, adjusted odds ratio; CI, confidence interval; ICU, intensive care unit; OR, odds ratio.
aThe multivariable ICU analysis was adjusted for patient age, occurrence of encephalopathy, existence of prematurity, admission year, Canadian Immunization Monitoring Program, Active (IMPACT) hospital, and evidence for diagnosis. The multivariable death analysis was adjusted for patient age, admission year, IMPACT hospital, and sex.
bPrematurity was defined as birth at <37 weeks’ gestation.
cThe subanalysis included case-patients aged 3 to 4 months with laboratory-confirmed pertussis who received >1 vaccine dose or were unvaccinated.