The effect of the COVID-19 pandemic on influenza-related hospitalization, intensive care admission and mortality in children in Canada: A population-based study

Abstract

Background: The COVID-19 pandemic resulted in unprecedented implementation of wide-ranging public health measures globally. During the pandemic, dramatic decreases in seasonal influenza virus detection have been reported worldwide. Information on the impact on paediatric influenza-related hospitalisations is limited. We describe influenza-related hospitalisation in children in Canada following the onset of the COVID-19 pandemic.

Methods: Data on influenza-related hospitalisations, intensive care unit (ICU) admissions and in-hospital deaths in children across Canada were obtained from the Canadian Immunisation Monitoring Program, ACTive (IMPACT). This national active surveillance initiative comprises 90% of all tertiary care paediatric beds in Canada. The study period included eleven influenza seasons, from the 2010/2011 season until the 2020/2021 season inclusive. Time series modelling was used to compare the observed to predicted influenza-related hospitalisations following the COVID-19 pandemic.

Results: Following the COVID-19 pandemic there was a significant decrease in paediatric influenza-related hospitalisations compared to predicted influenza-related hospitalisations for this time period (p < 0•0001). No paediatric influenza-related hospitalisations, ICU admission or deaths were reported for the 2020/2021 influenza season.

Conclusions: We show complete absence of paediatric influenza infection-related hospitalisation in a Canadian National Surveillance Network during the 2020/2021 influenza season. This significant decrease is likely related in large part to non-pharmacological public health interventions implemented during the COVID-19 pandemic, although the potential role of viral interference is unknown.

Funding: The Canadian Immunisation Monitoring Program, Active (IMPACT) influenza surveillance is a national surveillance initiative managed by the Canadian Paediatric Society and conducted by the IMPACT network of paediatric investigators on behalf of the Public Health Agency of Canada's Centre for Immunisation and Respiratory Infectious Diseases.

Keywords: COVID-19; Canada; Influenza; Paediatric.

Figure 1

Seasonal variation in influenza-related paediatric hospitalisation, ICU admissions and deaths before and during the COVID-19 pandemic. Panels (A) and (B) show monthly totals for influenza-related hospitalisation and intensive care unit (ICU) admissions; beginning1st September 2010 to 30th April 2021 inclusive for panel A (representing total study period 2010/2011 to 2020/2021 influenza seasons) and beginning 1st September 2018 to 30th April 2021 inclusive for panel B. Deaths per influenza season are shown in panel A (red cross). Canadian provincial and territorial governments declared emergencies with international travel restrictions initiated and school closures across Canada from mid-March 2020 (red dotted line). Panels (C) and (D) show the temporal distribution of influenza-related hospitalisations (C) and ICU admissions (D) in children from 1st September 2020 to 30th April 2021 inclusive compared with the average for pre-pandemic influenza seasons (black dotted line). The shaded area represents the maximum and minimum for the pre-pandemic seasons (from 2010/2011 to 2019/2020 influenza seasons inclusive).

Figure 2

Time series analysis of influenza-related hospitalisations for children in Canada for the period of 1st September 2010 to 30th April 2021 inclusive. Graph represents the monthly actual (crude) number of influenza-related hospital admissions and modelled numbers for each season with predicted numbers of admissions for the pandemic period (1st March 2020 to 30th April 2021 inclusive). (Spearman correlation of model fit, R = 0•93).