Why immunity debt doesn't exist, and why masks still matter

It is the conventional received wisdom that the ballooning of contagious diseases this winter, particularly among children, is an unavoidable corollary and result of COVID lockdowns and a whole cohort of young kids who haven't been exposed to the normal epidemiological rites of passage. 

This is often described as "immunity debt" or "deferred immunity", the idea that our immune systems have somehow become weak after 2-3 years of hiding behind masks and observing self-isolation and quarantine protocols. It is a very common belief and has been put forward by many individuals, from internet influencers to medical professionals to our own prime minister. The problem with this narrative is that it's almost certainly wrong, and this is not the way our immune systems work. It is not a "use it or lose it" situation.

The so-called "tridemic" of influenza, RSV and COVID has indeed been a trial for kids and parents alike this year, although it is starting to tail off now. (RSV in particular is usually at its worst in late fall and early winter.) The severity of this year's viral attacks is largely due to the impressive ability of viruses to mutate and adapt. That's just what viruses do, whether we are talking about COVID, influenza or the common cold.

However, what is becoming increasingly understood is that, much like measles and many other infectious diseases, COVID not only makes us sick, it also attacks our immune systems themselves, making them less able to protect us against other diseases as well as COVID itself. It seems likely that COVID is actually suppressing our immune systems and contributing to "T-cell exhaustion" (T-cells are the guardian cells that spot infections and help defend the immune system). Instead of "immunity debt", maybe we should be taking about "immunity theft".

It's hard to know, because we haven't been keeping track of COVID infections for many months now, but many epidemiologists believe that the more severe cases of the flu and RSV we are seeing are probably occurring among people who have already contracted COVID (whether they knew it or not), and who have had their immune systems compromised by it. Anecdotal evidence supports this, and an increasing number of studies are starting to back up this evidence.

The other aspect to this new information is that, contrary to the views of many politicians and even many healthcare professionals these days, masks and basic  public health measures are not part of the problem but an essential part of the solution. We should still be trying our best NOT to get infected with COVID, rather than pretending it doesn't exist and letting it all hang out.