People blame an ‘immune debt’ for the ‘triple’ of RSV, influenza and COVID affecting children across the country. But experts say this is misleading at best, and can be harmful

This fall, North American kids are not feeling well.

Children’s hospitals are filled with an unusually high number of patients infected with many different viruses – mostly RSV, influenza, and COVID, but also influenza-like viruses such as rhinoviruses and enteroviruses. Many are at or near capacity, and some are far beyond it, making room for an influx of patients into offices, gift shops, play areas, and parking tents.

Parents, pediatricians, and public health officials alike are asking the same question: How did we get here?

One popular idea that has been popping up in the public health community: The increase is due to “immunity debt,” a newly coined term. According to the theory, children have been exposed to fewer germs — COVID and otherwise — over the past three years because of pandemic precautions like masking and social distancing, and their immune systems have atrophied. Now that society has reopened, children are confronted with the usual petri dish of viruses with weakened defenses, causing an onslaught of disease – and possibly higher levels of disease and more seriousness than would otherwise have occurred.

But the experts luck We spoke with arguing that the theory is unscientific at best and destructive at worst, disagrees with any argument that COVID precautions harm the immune system, and emphasizes the wide range of factors leading to the current “triple pandemic.”

What is debt immunity?

When it comes to why kids hit so hard with viruses this fall, immunity debt is “certainly the most popular hypothesis,” Lyle Junker, MD, associate clinical professor of pediatrics at Harvard Medical System at Massachusetts General Hospital, said. luck.

The general idea is that babies born during an epidemic are protected from viruses they would normally have been exposed to if they interacted with more people – this weakened their defenses.

“These kids are now 1 year old, 2 years old, and they haven’t seen RSV previously,” she said. “They haven’t generally built up immunity, and now they get really sick.”

The immune debt theory was first proposed by French scientists in a 2021 opinion piece in The Infectious diseases now. Pandemic precautions such as masking and social distancing prevented hospital systems from being overwhelmed in the near term, flattening the so-called COVID curve and greatly limiting the spread of other pathogens. But they increased the likelihood of future epidemics, they wrote, “because of the increasing proportion of ‘susceptible’ people and the decline in herd immunity in the population.”

Since the article was published, discussion of the concept has proliferated, spreading from medical journals to Twitter and news outlets.

But some say the debate has shifted from a scientific discussion to a political one, with opponents of disguise using the theory to try to prove that the cover-up caused harm.

Dr. Amesh Adalja, an infectious disease specialist and senior research fellow at the Johns Hopkins Center for Health Security, believes the term is “misused and misinterpreted,” and that it “creates unnecessary political fighting on social media.”

Sarah Combs, an emergency medicine physician at Children’s National Hospital in Washington, D.C., said, “I don’t necessarily like ‘immunity debt’ becoming a coined phrase. luck.

“We know a lot of politicization has happened during the pandemic, and I’ve seen some people recover [the term] And they say: ah ha! It proves we were doing all the wrong things, that masking was bad and that we should never do it again.”

“I’m going to come out and say that’s absolutely wrong. To use that rhetoric that says, ‘Obviously no public health measures were needed,’ doesn’t work. That’s harmful.”

Dr. Jason Catanzaro, a pediatric allergist and immunologist at National Jewish Health in Denver, notes that masking used to be less common in some areas of the country — yet kids in those states are suffering just as much now during the triple pandemic.

“As far as I can tell,” he said, “no large area of ​​the country — red or blue — has been spared from RSV.”

Our immune systems were working fine.

Many experts luck We talked with saying that “immunity debt” isn’t the reason children’s wards are flooded with patients this year.

It’s not actually a scientific term, says Dr. John Bradley, medical director of infectious diseases at Rady Children’s Hospital-San Diego and distinguished professor at the University of California San Diego School of Medicine. luck. Catanzaro stresses that children’s immune systems did not stop working during the epidemic.

“They were still monitoring the cells for cancer, interacting with trillions of germs on a continuous basis to sort out the good bacteria and the bad,” he said. “Our immune systems were doing well.”

Instead, Bradley and Catanzaro think the increase is driven, in large part, by the huge cohort of kids with healthy immune systems, all of whom are returning to the community around the same time. They say their immune systems have not been weakened, but they may not have had the usual annual immunizations, or “boost” immunity through exposure to viruses without vaccines like RSV.

Catanzaro likens the children’s community in the United States to a young child entering daycare for the first time—and spends the next several months picking up what seems like every ailment under the sun.

“Is that considered an immunity debt?” Asked. He described how his daughter went through the common scenario of moving into child care before the pandemic. I don’t think her immune system was weak. You’ve never seen these things before.”

So many potential factors – and even more questions

Experts say there could be a myriad of factors behind the “pandemic triplet” in children — most of which are not viral.

Hospitals are understaffed, there are relatively few children’s hospital beds in the United States, and immunization rates among children have fallen over the past few years, leading to more infections. This could also be a worse-than-average flu year. The same may be true of RSV, which may have evolved to be more powerful than it used to be.

But some experts like Catanzaro and Juncker say more could be involved this fall. Many North American children returned to in-person learning last year, largely unconvinced, and the continent hasn’t seen the same surge in hospitalizations that it is seeing now.

“A large number of people were diagnosed with RSV in the middle of the epidemic, and there were no mass hospitalizations,” Catanzaro said.

“We weren’t closing intensive care units and filling hospitals,” Juncker added.

Both say it is possible that the coronavirus – which has infected the majority of the world’s population – has affected the immune systems of those previously infected, as much as measles can. COVID can alter the production of interferon, a substance produced by the body that helps the immune system fight infections and diseases such as cancer, according to Catanzaro.

So far, there is no evidence to prove this theory. Catanzaro said, citing a 2015 article in Sciences which “proved that measles suppresses pre-existing immunity to previous viruses”.

Bradley expects viruses like influenza and RSV to return to their usual seasonal patterns within a couple of years. He expects the coronavirus to eventually follow suit.

However, the question of why the triple epidemic is occurring is — and will continue to be — little more than an academic exercise for the millions affected this winter.

“There are a lot of people whose children are on oxygen with RSV who would like an answer,” Catanzaro said.