North American children are not doing well this fall.
Children’s hospitals are filled with an unusually high number of patients suffering from several different viruses – mainly RSV, influenza and COVID, but also influenza-like viruses such as rhinovirus and enterovirus. Many are at full or near capacity, and some are well above that, having made room for patient flooding in offices, gift shops, play areas, and parking lot tents.
Parents, pediatricians and public health officials are asking the same question: How did we get here?
A popular idea that’s emerged in the public health community: the surge is due to “immunity debt,” a newly coined term. According to the theory, over the past three years, due to pandemic precautions like masking and social distancing, children have been less exposed to germs — COVID and others — and their immune systems have atrophied. Now that society has opened up again, children are facing the usual petri dish of viruses with weakened defenses, causing an onslaught of disease – and perhaps greater levels and more severe disease than would otherwise have occurred.
But experts wealth saying that the theory is unscientific at best and destructive at worst, and contradicted any argument that COVID precautions damage the immune system, emphasizing a variety of factors that led to the current “triple disease”.
What is immunity debt?
When it comes to why kids are being hit so hard by viruses this fall, immunity debt is “definitely the most popular hypothesis,” said Dr. Lael Yonker, Harvard Medical System assistant professor of pediatrics at Massachusetts General Hospital Wealth.
The general idea is that children born during the pandemic were protected from viruses they would normally have been exposed to had they interacted with more people – and that it would have weakened their defences.
“These kids are a year old now, two years old, and they haven’t seen RSV before,” she said. “They haven’t built up immunity in general, and now they’re getting really sick.”
The theory of immunity debt was first proposed by French scientists in a 2021 advisory infectious diseases now. Pandemic precautions such as masking and social distancing prevented near-term overload of hospital systems, flattening the so-called COVID curve and greatly reducing the spread of other pathogens. But they increased the likelihood of future epidemics, the authors wrote, “due to a growing proportion of ‘susceptible’ people and declining herd immunity in the population.”
Since the article was published, discussion of the concept has exploded, spreading from medical journals to Twitter and news outlets.
However, some say the debate has shifted from a scientific discussion to a political one, with opponents of masking using the theory to prove that covering up causes harm.
dr Amesh Adalja, an infectious disease specialist and senior scientist at the Johns Hopkins Center for Health Security, says the term is “misused and misconstrued” and that it “creates unnecessary political struggles on social media.”
“I don’t really like it when ‘immunity debt’ becomes a coined term,” said Dr. Sarah Combs, Physician of Emergency Medicine at Children’s National Hospital in Washington, DC Wealth.
“We know there has been a lot of politicization going on during the pandemic and I’ve seen some people pick up [the term] and say: “Aha! It proves we did everything wrong, that masking was bad and that we should never do it again.’”
“I’m going to come out and say that’s dead wrong. Using this as rhetoric that says “clearly no public health action was required” doesn’t work. That is harmful.”
dr Jason Catanzaro, a pediatric allergist and immunologist at National Jewish Health in Denver, points out that masking has been much less common in some areas of the country — and yet children in those states are struggling just as much right now during the triple pandemic.
“As far as I can tell, there isn’t a significant area of the country – red or blue – that’s spared from RSV,” he said.
“Our immune system worked well”
Several experts who wealth said “immunity debt” isn’t the reason children’s wards will be flooded with patients this year.
It’s not actually a scientific term, says Dr. John Bradley, medical director for infectious diseases at Rady Children’s Hospital in San Diego and distinguished professor at the UC San Diego School of Medicine wealth. And children’s immune systems haven’t stopped working during the pandemic, Catanzaro claims.
“They were still monitoring cells for cancer and continually interacting with the trillions of microbiota to figure out which bacteria were good and which were bad,” he said. “Our immune system worked well.”
Instead, Bradley and Catanzaro believe the surge is largely being caused by a huge cohort of children with healthy immune systems all re-entering society at about the same time. Their immune systems haven’t been weakened, but they may not have received their usual yearly vaccinations or immunity “boosts” from exposure to non-vaccine viruses like RSV, they say.
Catanzaro compares the US pediatric population to a young child entering kindergarten for the first time — and spending the next few months struggling with seemingly every illness under the sun.
“Would that be considered an immunity debt?” he asked. He described how his daughter went through the usual pre-pandemic childcare transition scenario. “I don’t think her immune system was weak. She just had never seen these things before.”
Many possible factors – and even more questions
Experts say there could be a variety of factors behind the children’s “triple disease” – and most of them are non-virological.
Hospitals are understaffed and there are relatively few pediatric hospital beds in the US. Childhood vaccination rates have also declined in recent years, leading to more infections. And this could also be an above-average flu year. The same may be true of RSV, which may have grown more powerful than it once was.
But some pundits like Catanzaro and Yonker say there could be more at play this fall. Many North American children returned to in-person learning largely unmasked over the past year, and the continent has not seen the same spate of hospitalizations as it is now.
“Huge numbers of people were diagnosed with RSV in the middle of the pandemic and there were no mass hospitalizations,” Catanzaro said.
“We haven’t closed intensive care units and stuffed hospitals,” Yonker added.
Both say it’s possible that COVID – which has infected much of the world’s population – has taken a heavy toll on the immune systems of those previously infected, just as measles can. According to Catanzaro, COVID can alter the production of interferon, a substance the body produces that helps the immune system fight off infections and diseases like cancer.
So far there is no evidence to support this theory. But measles in unvaccinated children “can lead to immune amnesia,” Catanzaro said, citing a 2015 article Science which “demonstrated that measles eradicate pre-existing immunity to previous viruses.”
Bradley expects viruses like the flu and RSV to return to their regular seasonal patterns within a few years. And he expects COVID to eventually follow suit.
Still, the question of what caused the triple pandemic is – and remains – more than an academic exercise for the millions affected this winter.
“There are a lot of people out there whose kids are on oxygen with RSV and would like an answer,” Catanzaro said.