Significant Decrease in Pediatric Flu Hospitalizations Observed During COVID-19

Shaun K. Morris

As a result of the COVID-19 pandemic, there were significant decreases in seasonal influenza virus detection reported worldwide, with particularly limited data on the incidence of severe influenza in the pediatric population.

Led by Shaun K. Morris, Division of Infectious Diseases, The Hospital for Sick Children, University of Toronto, a team of investigators determined the impact of the COVID-19 pandemic on influenza-related hospitalization and mortality in children in Canada, utilizing data from 11 influenza seasons.

They observed a significant decrease in pediatric influenza-related hospitalizations following the onset of the pandemic, with a complete absence of pediatric influenza infection-related hospitalization in Canada during the 2020 - 2021 influenza season.

Methods

Investigators performed a prospective active surveillance based observational study using data on influenza-related hospitalizations, ICU admissions, and in-hospital deaths in children across Canada. This was obtained from the Canadian Immunization Monitoring Program, ACTive (IMPACT).

They noted the data was collected from 12 participating pediatric centers and represented 90% of all tertiary care beds in the country. An influenza-related hospitalization was defined as any patient aged ≤16 years admitted to hospital with laboratory-confirmed wild-type influenza virus infection.

A total study period included 11 influenza seasons from the 2010 - 2011 season unit the 2020 - 2021 season, chosen to include 10 full influenza virus seasons before 2020. They defined March 2020 as the onset of the COVID-19 pandemic, due to the World Health Organization declaration.

They used time series modeling to compare the observed to predicted influenza-related hospitalizations following the COVID-19 pandemic.

Findings

In the pre-pandemic period, the total number of pediatric influenza-related hospitalizations was 9036, from which 8598 (95.2%) occurred between September - April. Then, in the pandemic period, there were only 3 pediatric influenza-related hospitalizations reported in April 2020.

Data show in comparison there were 120 pediatric influenza-related hospitalizations that occurred in March 2020, while the average for April during the pre-pandemic period was 92 cases (53 - 210).

During the entire pandemic period, there were 126 pediatric influenza-related admissions reported, which was significantly lower than predicted for the period which totaled 2227 (P <.00001). Throughout the 2020 - 2021 influenza session, there were 0 pediatric influenza-related hospitalizations reported, with predicted number of hospitalizations at 1638.

Further, data show the average total number of pediatric influenza-related ICU admissions during each influenza season in the pre-pandemic period was 141 (59 - 255), while the average rate of ICU admissions per 100 pediatric influenza-related hospitalizations was 15.9 during the pre-pandemic period. There were 0 pediatric influenza-related ICU admissions in the 2020 - 2021 season.

Additionally, no influenza-related pediatric ICU deaths were reported during the 2020 - 2021 influenza season.

Takeaways

Overall, investigators noted that while the cause of decrease in pediatric influenza-related hospitalizations following the onset of COVID-19 is not fully understood, public health measures put into place during the pandemic may have played a major role.

“With the potential for a rebound in seasonal influenza infections amongst children on relaxation of pandemic control measures, ongoing surveillance and increased understanding of the reasons underlying the observed decreases in paediatric influenza-related hospitalisation are of utmost importance,” investigators wrote.

The study, “The effect of the COVID-19 pandemic on influenza-related hospitalization, intensive care admission and morality in children with Canada: A population-based study,” was published in The Lancet Regional Health Americas.