Outcomes of immunocompromised children hospitalized for Influenza, 2010-2021, the Canadian Immunization Monitoring Program Active (IMPACT)

Abstract

Objectives: To evaluate immunocompromising conditions and subgroups of immunocompromise as risk factors for severe outcomes among children admitted for influenza.

Methods: We performed active surveillance for laboratory-confirmed influenza hospitalizations among children ≤16 years old at the 12 Canadian Immunization Monitoring Program Active hospitals, during 2010-2021. Logistic regression analyses were used to compare outcomes between immunocompromised and non-immunocompromised children, and for different subgroups of immunocompromise. The primary outcome was intensive care unit (ICU) admission; the secondary outcomes were mechanical ventilation and death.

Results: Among 8982 children, 892 (9.9%) were immunocompromised; these patients were older (median, 5.6 (IQR, 3.1-10.0) vs. 2.4 (1-6) years; p < 0.001) than non-immunocompromised children, had a similar frequency of comorbidities, excluding immunocompromise and/or malignancy (38% (340/892) vs. 40% (3272/8090); p 0.2), but fewer respiratory symptoms, such as respiratory distress (20% (177/892) vs. 42% (3424/8090), p < 0.001). In multivariable analyses, immunocompromise (adjusted odds ratio (aOR), 0.19; 95% CI, 0.14-0.25) and its subcategories immunodeficiency (aOR, 0.16; 95% CI, 0.10-0.23), immunosuppression (aOR, 0.17; 95% CI, 0.12-0.23), chemotherapy (aOR, 0.07; 95% CI, 0.03-0.13), and solid organ transplantation (aOR, 0.17; 95% CI, 0.06-0.37) were associated with decreased probability of ICU admission in children admitted for influenza. Immunocompromise was also associated with a decreased probability of mechanical ventilation (aOR, 0.26; 95% CI, 0.16-0.38) or death (aOR, 0.22; 95% CI, 0.03-0.72).

Conclusion: Immunocompromised children are overrepresented among hospitalizations for influenza, but have a decreased probability of ICU admission, mechanical ventilation, and mortality following admission. Admission bias precludes generalizability beyond the hospital setting.

Keywords: Canada; Children; Disease severity; Hospitalized; Immunocompromised; Immunodeficiency; Immunosuppression; Influenza; Intensive care; Mortality.