Is Immunity Debt Real? Two Experts Debunk The Health Phenomenon

You’ve read the headlines, likely know a friend struggling with a stomach bug or a case of respiratory syncytial virus (RSV) in their household, or somebody who has even made a trip to the hospital recently with a sick kid. It seems like everyone is down with something. But did all the Zoom schooling, working from home and virtual socializing of the past few years really put our immune systems at a disadvantage—a phenomenon dubbed “immunity debt”? “The answer is more complex than we would like,” says Dr. Samira Jeimy, a clinical immunologist at the London Health Sciences Centre in London, Ont.

Chatelaine asked two experts what you need to know about immunity debt.

Where the concept of immunity debt originated

You won’t find mention of immunity debt before March 2020; it’s a product of COVID-19 pandemic times. The term originated in a 2021 position paper published in the journal Infectious Diseases Now, where a French research team hypothesized that, thanks to COVID protection measures like masking and lockdowns, kids were experiencing a lack of immune stimulation due to a reduced exposure to the usual viruses, which could induce an immunity debt.

Unfortunately, how the term has been used more widely is misleading, says Dawn Bowdish, executive director of the Firestone Institute for Respiratory Health and professor at the McMaster Immunology Research Centre in Hamilton, Ont. The concept has been extrapolated to adults and used to argue that pandemic health measures have had lasting negative effects on all of our immune systems, contributing to a mass paranoia about getting sick post-COVID-19. “To be honest, I think it’s done more harm than good,” she says.

Have pandemic measures left our immune systems under-stimulated?

No, says Jeimy: “The immune system is constantly exposed to viruses and bacteria.” Despite the amount of isolation we all experienced when pandemic lockdown measures were in place, our immune systems were still working hard. “In the background, it’s busy all the time—it’s not like it ever goes latent,” says Jeimy. And there is no reason to think our immune systems need to catch up, she says.

Some say you need to get sick to develop a healthy immune system. Is it true?

Not necessarily. “It’s an idea that sounds intuitive, but there isn’t a lot of evidence supporting that,” says Bowdish. The notion that once you’ve had a particular virus you have more protection against it doesn’t always hold up. If it did, certain people wouldn’t be predisposed to repeat urinary tract infections or lung infections, for example. “And we know that you can catch the same cold twice within one cold and flu season,” says Bowdish.

The immune system does get faster at dealing with pathogens it’s been in contact with before, and some viruses will offer you some measure of future protection, but many—including RSV and COVID-19—are also very good at sneaking under immune responses, says Bowdish.

It’s worth pointing out that both doctors stress it’s never a good idea to intentionally get sick in the hopes of acquiring a boost of immunity. (You may have heard of some people going about trying to get sick, in the hopes of acquiring antibodies.) “Nobody should seek out a respiratory infection, because in the process of getting sick you could be damaging your organs or creating other short-term and long-term health issues,” says Jeimy.

Many people—and in particular, children—have been more sick this winter than in seasons past. How are we to understand this?

The prolonged public health restrictions over the past few years may have left kids’ innate immunity less ready to deal with the seasonal wave of respiratory viruses—including the flu, the common cold and RSV—circulating in recent months. More kids are catching illnesses and passing them on to their parents, grandparents and other adults in their circles. And, many adults are getting sick, too—though we don’t know with any certainty if that’s a direct cause of pandemic restrictions.

There’s also the fact that some children who would have been infected with RSV for the first time a year or two ago are just encountering it now, along with cohorts of younger kids—leading to a greater number of kids grappling with the virus in one season. (A child’s first RSV infection is typically the worst, and more likely to land a little one in hospital.)

Plus, many pregnant persons who did not receive COVID-19 or flu vaccinations, or who were not exposed to RSV during isolation measures, did not pass along protection to their babies, who may now be encountering the viruses for the first time with more serious outcomes, says Bowdish. Add to all that the impact of the acetaminophen shortage, which likely resulted in more feverish babies and toddlers landing in emergency rooms, and we have a number of factors at play that have contributed to the high hospital admission rates this winter.

So, is there any truth to the idea of immunity debt?

That depends on how you interpret the phrase—and who you ask. If we mean that everybody seemed to be getting sick with everything all at once this winter, because we had to employ precautions to slow COVID-19 during the past few years, then the idea of immunity debt is somewhat true.

But you certainly can’t apply the term to one specific virus. “The concept is not totally consistent with what we are seeing with RSV infections, and it does not apply to influenza at all since influenza changes every year,” says Bowdish. “The term ‘immunity debt’ also wouldn’t apply to COVID-19, which is a new infection,” she says.

There is an outstanding question about how COVID-19 infections have affected our immune systems that needs further exploration, says Jeimy. “There’s an immune dysregulation happening post-infection that’s not really being acknowledged yet,” she says. We don’t yet know the impact COVID-19 has on our immune systems long-term. This could help to explain why kids seem more vulnerable to respiratory infections and could be to blame for an acknowledged uptick in bacterial infections, like pink eye.

If exploring the notion of immunity debt means diving deeper into the long-COVID-19 phenomenon, that could be a positive outcome, says Jeimy. “Hopefully we can come up with better understanding and ways to deal with these emerging post-viral disease consequences.”

This story has been updated to clarify Dawn Bowdish’s job title.