Severe Respiratory Disease Among Children With and Without Medical Complexity During the COVID-19 Pandemic.

Importance: Severe respiratory disease declined during the COVID-19 pandemic, partially due to decreased circulation of respiratory pathogens. However, the outcomes of children with higher risk have not been described using population-based data. Objective: To compare respiratory-related hospitalizations, intensive care unit (ICU) admissions, and mortality during the pandemic vs prepandemic, among children with medical complexity (CMC) and without medical complexity (non-CMC). Design, Setting, and Participants: This population-based repeated cross-sectional study used Canadian health administrative data of children aged younger than 18 years in community and pediatric hospitals during a pandemic period (April 1, 2020, to February 28, 2022) compared with a 3-year prepandemic period (April 1, 2017, to March 31, 2020). The pandemic period was analyzed separately for year 1 (April 1, 2020, to March 31, 2021) and year 2 (April 1, 2021, to February 28, 2022). Statistical analysis was performed from October 2022 to April 2023. Main Outcomes and Measures: Respiratory-related hospitalizations, ICU admissions, and mortality before and during the pandemic among CMC and non-CMC. Results: A total of 139 078 respiratory hospitalizations (29 461 respiratory hospitalizations for CMC and 109 617 for non-CMC) occurred during the study period. Among CMC, there were fewer respiratory hospitalizations in both 2020 (rate ratio [RR], 0.44 [95% CI, 0.42-0.46]) and 2021 (RR, 0.55 [95% CI, 0.51-0.62]) compared with the prepandemic period. Among non-CMC, there was an even larger relative reduction in respiratory hospitalizations in 2020 (RR, 0.18 [95% CI, 0.17-0.19]) and a similar reduction in 2021 (RR, 0.55 [95% CI, 0.54-0.56]), compared with the prepandemic period. Reductions in ICU admissions for respiratory illness followed a similar pattern for CMC (2020: RR, 0.56 [95% CI, 0.53-0.59]; 2021: RR, 0.66 [95% CI, 0.63-0.70]) and non-CMC (2020: RR, 0.22 [95% CI, 0.20-0.24]; RR, 0.65 [95% CI, 0.61-0.69]). In-hospital mortality for these conditions decreased among CMC in both 2020 (RR, 0.63 [95% CI, 0.51-0.77]) and 2021 (RR, 0.72 [95% CI, 0.59-0.87]). Conclusions and Relevance: This cross-sectional study found a substantial decrease in severe respiratory disease resulting in hospitalizations, ICU admissions, and mortality during the first 2 years of the pandemic compared with the 3 prepandemic years. These findings suggest that future evaluations of the effect of public health interventions aimed at reducing circulating respiratory pathogens during nonpandemic periods of increased respiratory illness may be warranted.