Alberta study shows 'reassuring' trends in childhood hospitalization patterns post-pandemic

A new University of Calgary study shows that while hospitalizations for respiratory illnesses among Alberta children surged after pandemic-related measures were lifted, there has since been a return to more typical levels.

The study, published in the Lancet Regional Health - Americas, analyzed 52,839 pediatric hospitalizations for the most common causes of acute respiratory disease — including bronchiolitis (mostly caused by RSV), influenza-like illness, pneumonia, COVID-19, croup and asthma — over a 14-year period ending on Aug. 31, 2024.

"This is a story that's unfolded in chapters, from before COVID to during COVID, and now we've had the chance to look at … a couple of years after the peak of the pandemic," said Dr. Jim Kellner, the lead author and pediatric infectious diseases specialist with the University of Calgary.

Researchers tracked hospitalizations at Alberta Children's Hospital, Stollery Children's Hospital and all 95 other Alberta facilities that admit kids and they were able to quantify the dramatic swings that made headlines over a number of years.

They found typical patterns were disrupted — and there was a "significant decline" in pediatric hospital and intensive care unit admissions for these respiratory conditions — early during the pandemic when public health measures, including masking and school closures, were in place.

Hospitalizations dropped by 91 per cent during the winter of 2020-21.

This was followed by a dramatic jump during the 2022-23 respiratory virus season, with the incidence of hospitalization surging to 48 per cent above average pre-pandemic levels.

Bronchiolotis, which is often triggered by RSV, was the key driver of this surge, the study showed.

That respiratory virus season, which came after public health measures were lifted, was dubbed the "triple-demic" as hospitals were overwhelmed with children who were sick with RSV, influenza and COVID-19.

Hospitalizations dropped

"There were concerns that if children weren't exposed to mild forms of these infections — that they would have to be exposed to sometime — that somehow it would affect individual children and their immunity in a way that could be causing long-term problems," said Kellner, who also works at Alberta Children's Hospital.

There were also worries there would be permanent changes to the seasonal patterns of infections that would make them more unpredictable and harder to plan for and manage in the health system, according to Kellner.

But by the winter of 2023-24, the researchers found hospitalizations and ICU admissions for acute respiratory disease among children returned to expected pre-pandemic levels.

"We've seen a return to more or less how things were before, which was different than what people were expecting," he said, noting more research is needed to watch the ongoing trends.

Kellner said the average age of admitted children (normally the very young) didn't increase compared to pre-COVID years, and the proportion of kids who got very sick was similar to previous levels. 

The findings suggest any increase in susceptibility to infections — among individual children or in the population at large — related to pandemic measures "may have largely resolved by the winter of 2023-24," the authors wrote.

"[The study] is a nice addition to the scientific literature to help us understand partly what happened during these tumultuous years," said Dr. Jesse Papenburg, a pediatric infectious disease specialist at the Montreal Children's Hospital and McGill University, who wasn't involved in the study.

• New RSV shot not available to Alberta newborns as virus season ramps up
• Most RSV infections are in babies less than 1 year old. But protection remains out of reach for many

He noted researchers identified cases based on the symptoms children presented to hospital with, rather than analyzing positive test results.

That, he said, provides a more complete picture because the findings are not impacted by the availability of testing.

"It is reassuring that we returned to a kind of normalicy or typical respiratory season both in terms of timing and the number of cases we saw. And also didn't see big shifts in the age distribution either in this study," said Papenburg.

"[With] the interventions that we did to try and curb the spread of COVID-19, there's no evidence there was any sort of longer term harm or disruption in our wintertime respiratory infections that would have caused some sort of prolonged burden."

Papenburg said the data also underscores the true burden of illnesses such as RSV and influenza among children.

And he believes it highlights the need to ensure a new injection to protect babies from RSV is made available in provinces such as Alberta, and to increase flu vaccination rates.

Meanwhile, Kellner said the study should help with health system planning because it illustrates the large seasonal peaks — and demand during the fall and winter seasons — that hospitals can expect.