Covid is not destroying kids immune systems

Conspiracy theories abound on the internet. They are wrong.

This article was written in collaboration with Dr Andrew Croxford, an immunologist with a career spanning academia and industry, specialising in the inflammatory mechanisms driving human disease.

Covid-19 is a nasty illness, although thankfully less threat today thanks to widespread vaccination and a wall of so-called ‘hybrid immunity’ - the swathes of our population who now have immunity from both infection (largely from omicron) and vaccination. 

Nonetheless, SARS-CoV-2 has been responsible for millions of deaths and a significant amount of morbidity. You would think that there was no need to invent things to make it seem any worse than it is.

Alas. Here is a post to debunk one of the more extreme myths which has evolved online around the after effects of SARS-CoV-2; namely that Covid-19 causes some sort of immunodeficiency in healthy kids.

Where did this come from?

As with most myths, this one starts from an online echo-chamber; this time of groups who support the notion of “Zero Covid”. This myth is fuelled by serious overinterpretation of basic research and simple misunderstanding of clinical findings. They frequently ignore even the most striking limitations of any given study before sharing with an anxious audience.

SARS-CoV-2, like many (if not all) viruses does exert effects on immune cells. There are a number of ways in which Covid-19 alters different facets of the immune system to suppress them during and after the acute infection, altering ratios of immune cells found in the blood (not all of which are indicative of ‘dysregulation’ or ‘deficiency’). For the vast majority of people, these perturbations are transient and resolve shortly afterwards. This is the shape of a normal, healthy immune response.

There are also some hyperinflammatory changes which can occur for longer periods after Covid-19 that may be linked to different post-covid syndromes (often referred to as long covid). The clinical relevance with regard to subsequent infections is unclear, and there is no indication at present that they impact the normal functioning of the immune system in protecting the body.

Studies on these topics often contain very technical, high-dimensional data that few people are well equipped to interpret. The complex language and content makes it easy for motivated individuals to mislead others, extrapolating obscure, non-reproducible findings to entire populations of healthy individuals. Sometimes they also simply don’t know what they’re sharing (less the title and perhaps the abstract).

We see a similar strategy employed by the anti-vaccine movement and, without question, striking similarities have emerged at both extremes of this saga.

Why has this taken hold recently?

Something we have discussed previously is that the measures taken during the pandemic to slow the spread of Covid-19 also impacted many other infectious diseases. Many of these like RSV, Flu or group A Strep (GAS) normally have a seasonal pattern of infection which is influenced heavily by population immunity.

It was predicted back in 2020 that these measures would disrupt the patterns of these infections, and that reduced exposure over a long period of time would also reduce population immunity, resulting in unusual surges of infection once they returned.

As predicted, this is what has been observed to varying degrees with these pathogens over the past 18 months or so. Some countries have had particularly nasty surges of RSV or Flu, and the UK is currently experiencing an unusual surge in GAS. Some countries even experienced these before any significant waves of Covid (e.g. Australia, New Zealand and Japan),.

These unusual patterns of infection have provided fodder for this immunodeficiency myth - but these trends are adequately explained without the need to invent long lasting damage to our collective immunity. Perhaps unsurprisingly, this has mainly been pounced upon by groups who are strongly promoting much more aggressive measures to contain Covid-19 and would not want negative after effects to be associated with them.

Why it is wrong epidemiologically

Before we get into the immunology, let’s first explain why this makes no sense just based on the epidemiology.

First of all, let us remember this was predicted long before it happened, because it is a predictable outcome of reduced exposure to seasonal pathogens whose transmission is heavily influenced by population immunity.

Take the well-known fact that RSV is contracted by around 90% of children in the first 2 years of life, with half of them having had it twice! We can imagine how regularly they are usually exposed to infectious doses of this particular bug.

In addition, in places which have experienced particularly severe waves of RSV, the vast majority of cases are in infants <6m of age or even younger. This age group is the least likely to have even been previously infected with Covid-19 because they have not been alive long enough! This just happens to be the age which is highest risk from severe illness if infected, and there were lots of infections.

Let us also not forget this phenomenon was first observed in countries which, at the time, had experienced absolutely negligible rates of Covid-19 infection (Australia, New Zealand, Japan). It was impossible for it to have been caused by Covid-19 infections at these locations.

For Group A Strep, immunity gained by adulthood is thought largely to be a result of accumulation of anti-Strep A antibodies, and that repeated exposure builds immunity which prevents future infection. With near zero cases in children for 2 years during the pandemic, we can safely assume there is lower population immunity than would be expected to blunt transmission.

This is not to say that all these patterns are explained entirely by differences in population immunity alone, because seasonal transmission is complex and different for different pathogens; influenced by climate, behaviour, international seeding and viral interference among other things. But on the whole, nothing truly surprising has happened.

In addition, study after study confirms that infection provides robust protection against reinfection (including omicron subvariants). Far from causing immunodeficiency, SARS-CoV-2 infection actually stimulates a highly effect immune response to itself!

With regard to the hundreds of other viruses yet to be encountered, the immune systems of young children will continue to generate and replenish the body with an abundance of young, so-called ‘naïve’ B and T cells, from the bone marrow and thymus, respectively, in spite of SARS-CoV-2 infection. These cells are created and designed to cope with whatever viruses they will likely encounter.

Finally, what has been observed so far is absolutely not what would be expected if there were truly a clinically relevant immunodeficiency caused by Covid-19. What has been observed is largely just more of what we would see normally - increased volume of normal types of infection (some less severe, some more severe).

The hallmark of immunodeficiency is not just more normal infections - it is an increased frequency (not easily explained by other mechanisms as is the case for the recent waves) or unusually severe infections, or most obviously infections caused by organisms which would not normally cause infection in people with normally functioning immune systems. We would expect to see otherwise healthy people with severe, reactivated varicella (chicken pox virus), fungal pneumonias or cryptococcal meningitis, among other things.

Why it is wrong immunologically

Immunology is extremely complicated - so complicated that much of it is still not well characterised. We fit a lot of immunology into very simplistic mental models to make sense of it, but the reality is much more complex. Combining this with extremely sensitive tools to look at cell behaviour can mean finding a lot of stuff, not all of which will translate to a functional impact.

Studies that identify immune changes during or shortly after infection, or only look at hospitalised people with severe disease, exclusively elderly patients, or autopsy patients (who died, by definition), or only patients who are suffering prolonged sequelae of infection are obviously not representative of the vast majority of people, especially children.

This is even more relevant in the current era of over 99% of the population having some form of existing immunity, who will go on to largely have a relatively mild illness with no clinically relevant sequelae.

What may be true of Covid-19 (and is certainly true of many respiratory viruses) is that during the acute infection and a brief period afterwards you may be more vulnerable to infections with bacteria; so called superinfections. But this phenomenon ‘does not an immunodeficiency make’.

Bacterial superinfections following viral infection are thought to be one of the contributing factors to the current wave of severe infections with GAS in the UK (although interestingly it is mainly Flu and other viruses, not Covid-19 - make of that what you will).

A healthy amount data points to perfectly normal responses to a virus for kids with Covid-19, with expansions of CD8, CD4 and B cell types, primed to act in concert, fighting the acute infection that piqued their interest in the first place. The fact that children respond well to COVID is reflected not only in the clinical outcome, but also at the immunological level.

Consider the kerfuffle about ‘T cell exhaustion’. Elevated PD-1 expression on cytotoxic T cells is not necessarily indicative of exhaustion , but rather a protein that can be detected once they are activated. Another one – the furore around “loss of naïve T cells”. This is not exactly reproducible nor common across multiple studies (see here and here).

There has been too much extrapolation, cherry picking and narrative-over-consensus taking place. It has sadly left many people who get their information from social media left with a seismic misunderstanding of their own risk, and the risks posed to their children.

Calling Covid-19 “Airborne AIDS” is appalling, and should genuinely be disqualifying for any commentator. Moreover, it is offensive to those who may are suffering from true severe immunodeficiency syndromes. You will not find any respectable immunologists who are working on Covid-19 espousing the idea that it causes anything of the sort, and in fact most are quite ardent this is not the case.

Remember, *every* virus is new to a young child if they catch if for the first time. There are some children at higher risk, and very rare outcomes can-and-do present clinically. The reality is that the kids are doing just fine and are surely happy to be back in school, doing what kids do best.

Conclusion

Covid-19 can cause transient alterations to the immune system during and shortly after acute infection which is consistent with other respiratory viruses. There is no evidence Covid-19 cause any long term immunodeficiency. There is no evidence Covid-19 infections have had a meaningful impact on unseasonal or unusual surges in other infections, which were largely predicted as a result of suppressed transmission during the pandemic.

If your trusted source of Covid-19 information is saying otherwise, it’s time to find a new source.