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Dr. Fahad Razak and Dr. David Naylor are professors in the department of medicine at the University of Toronto. Dr. Razak is on staff at Unity Health Toronto.

Across Canada and around the world, health care facilities are facing a massive surge in the number of children afflicted with serious respiratory illnesses. Why is this happening and how do we respond?

In some ways, this is no surprise. Each fall, children’s hospitals prepare for a seasonal surge of hospitalizations due to flu, RSV and other viruses. With waves of COVID-19 having prompted the widespread use of masks in public settings, along with the closures of schools and other programs that bring children together, the usual seasonal viruses and RSV cases were strikingly reduced in recent years. For example, a typical flu season sees approximately 1,500 children hospitalized across Canada, but a 2021-2022 national study found zero documented cases.

With pandemic measures lifted, children have been congregating again, with more indoor activity. This includes a cohort of our youngest children, who have limited exposure to endemic viruses because of pandemic protections. The result has been a much larger number of children who are getting their first infections from respiratory viruses, which tend to be more severe, particularly in children under the age of five. At the present time, the flu and RSV are taking a considerable toll on this age group.

There is ongoing concern that this surge could be due to immune-system dysregulation among the very high proportion of children worldwide who have been infected with COVID-19. A strong counterfactual point to this theory, however, is New Zealand’s massive surge in RSV, which occurred in the middle of 2021 during their winter season. This was observed before Omicron swept through pediatric populations worldwide and in a country that stringently contained COVID-19. With further reopening in 2022, New Zealand’s two influenza-free years ended with a massive surge. Also noteworthy is Britain’s experience, where COVID-19 infection rates were higher than in Canada. Detailed modelling has found that the size of recent RSV surges in Britain aligns with what we would expect to happen after public-health measures led to long-term nonexposure to certain viruses.

SARS-CoV-2 has been full of nasty surprises, and immune dysregulation as a factor bears further study. However, rational consideration of competing or complementary causes has been difficult given that some insist on describing delayed first exposures among the children of the pandemic as an “immunity debt.” Critics of public-health measures have seized on that language to argue that the current surge shows the folly of not letting COVID-19 and other viral diseases spread “naturally,” and argue that the purported solution is to repay this “debt” quickly by allowing infections to spread now.

This revisionist history is nonsensical, and the proposed solution – turning sick children into a form of communal currency – is perverse. Slowing the spread of viruses by asking the public to don masks doesn’t kick the proverbial can down the road. First, it reduces the dangerous overloading of pediatric hospitals and clinics, enabling better care for children with seasonal illnesses as well as children with other health challenges. Second, it allows those at the highest risk of severe RSV – infants under the age of six months – to get a bit older and stronger before their first exposure. Third, while there is currently no vaccine for RSV, slowing its spread also provides more time for parents and children to get up to date with this year’s tightly-matched flu shots. Unfortunately, the uptake of flu vaccines remains particularly spotty among younger children, even though these vaccines can be given safely as early as six months old.

Like many Canadians, we’re also tired of hearing about COVID-19 or other viral illnesses, irked by governments blaming each other for the failings of Canada’s health care systems, and worried about the world that our children and grandchildren are going to inherit. Right now, however, our youngest citizens are getting seriously ill and we have already outstripped our baseline pediatric ICU capacity. Masks and vaccines are not panaceas. However, with a smart deployment of these measures, the spread will continue at a slower and more manageable rate, with fewer severe cases of flu. The residual unexposed cohort will be much smaller next year, and, based on ongoing research, we may finally have an RSV vaccine by then.

In short, there’s an urgent need for a major campaign to vaccinate Canadian children against this year’s flu strain. Amid strong indications that this multi-viral surge has staying power and will take a toll even as it recedes, we also believe that masks should be required over the next few weeks in public indoor settings – including, with all due flexibility, in schools. Many will object vehemently. To them, we would simply ask: if not now, with so many children ill and our pediatric hospitals in crisis, then when?