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COVID’S LONG TAIL – autoimmunity – Dr. Bannon's Blog

COVID19 is not in the news much nowadays, after all, the pandemic is officially over. All the same the virus continues to be a significant part of modern life, with 1,500 COVID linked hospital admissions last week, 150 deaths with COVID on the death certificate, as well as the evolving long-term effects.

This is brought back to my mind by the sound of male chaffinch’s call, repeated many times a minute for the entire waking day and which reminded me of the silence of March 2020 when lockdown started, and the human world went quiet. Every year the charming birds evokes the feeling of that strangest of times. 

It was brought back to be more directly by my own recent COVID infection, likely my first. It was manageable, but enough to remind me it remains an unpleasant experience  with cough and a month of fatigue its main features in my case. My immunity gained from vaccination and boosting meant I was a long way from needing any medical help, apart from inhalers to manage the viral induced exacerbation of asthma. In ten years when I would be 78, it might have been another matter. 

So, four years after the pandemic’s onset, we are all familiar with the frequently miserable short-term effects of COVID19, but what more do we know about its wider or longer effects?  I’ll start with autoimmunity. 

COVID and autoimmune arthritis.

One of the disturbing messages given out by professional antivaxxers was that COVID vaccines should be avoided by anyone with autoimmune disease, as well as spreading the idea that the vaccines would cause autoimmunity directly. There was no good science behind this and genuine experts were saying exactly the opposite. 

This recent paper sheds some light on how it played out in reality. Korean researchers have huge health databases at their disposal, one of the many benefits of nationwide health systems. Using it they were able to compare the incidence of autoimmune arthritis after COVID and compare them to those after flu in 22 million Japanese and South Koreans.

They found an 22% increase in autoimmune arthritis after COVID compared to uninfected controls, and of 30% when compared to flu. They also found that a single COVID vaccination reduced this risk by 40%, two by 60% and that the risk of developing arthritis was increased by severe disease.

While the actual risk is of course low, such numbers will translate into a significant number of individuals with arthritis needing treatment and as well as a more significant number who will have avoided the problem by vaccination.

What about vaccination itself? Like any medication, there are side effects. This 2023 study found 45 cases of various forms of arthritis linked to COVID vaccination and concluded that it is a real, though vanishingly rare side effect:

“However, even if there is a cause-and-effect relationship, related complications are relatively rare. Joint symptoms have improved or have been completely cured after treatment, which may be a transient response to the vaccine”

Other autoimmune diseases

Another study from Hong Kong, similarly using huge health databases, included 1,028,721 COVID-19 and 3,168,467 non-COVID individuals and revealed a significant increase in risk of various autoimmune diseases after COVID 19 and again why vaccination is a good idea for anyone with or at risk of autoimmunity. Its findings are displayed in the forest plot below:

Figure thumbnail gr4

Increase risk to the right of the vertical line, decreased risk to the left.

Many of the actual numbers are small and the effects uncertain – shown if the horizontal line crosses 1.

These studies are reassuring to those with autoimmune disease that vaccination is a good idea. 

What about the brain?

Autoimmune diseases are caused by interactions between the genes we inherit and environmental factors, of which viral infections are one. MS, for example, is highly likely to be at least in part, due to infection in adolescence with Epstein Barr virus, the culprit behind Glandular Fever.  What about Sars-Cov2?

Early in the pandemic cases were reported emerged of MS being diagnosed after COVID infection, with the suggestion that viral proteins might mimic those in the brain, leading to an autoimmunity. Thankfully this hasn’t played out as far as I can see, and indeed, for those with MS, mild to moderate infection itself doesn’t seem to cause increases in relapses or disability. 

Antivaxxers, of course, claim that anything that happens after vaccination is due to vaccination spread and MS if no exception. This was spread by the You Tube ‘star’ Dr John Campbell who is a startling example of how audience capture can lead to extreme views and could reasonably be seen as our own leading pandemic conspiracist.  and was easily debunked.  Vaccines do not cause relapses in people with MS, nor do they cause it to be diagnosed.

However, persistent symptoms are more common in people with MS, and the risk linked to previous levels of disability, depression and being female. 30% of people with MS experienced symptoms for more than 4 weeks and about 12% for more than 12 weeks. Thankfully, people with MS are likely to be vaccinated and more likely to have taken social distancing and mask wearing seriously. Friends of mine with MS were right to be cautious.

COVID’s persistent effect on the brain is likely to be due to ongoing inflammation, plus a multitude of potential immune and non-immune mechanisms described here. How this translates into how people function in the long term who knows, we will have to wait and see.  The graphic below shows how COVID can affect the brain though interaction with ACE receptors, damage to blood vessels and directly though hypoxia. 

Details are in the caption following the image

Dementia and COVID

There are concerns regarding potential problems with dementia; accelerating the onset for those at risk of dementia, and worsening symptoms for those who already have it. Again, this will be defined as time goes by, but it is not rocket science to believe that any serious infection will tend to exacerbate the risk of another diagnosed or latent problem.

In summary, now that most of the world’s population has been infected by COVID at some point, its effect on autoimmunity is becoming apparent. One important conclusion is that the more severe the infection the greater the risk. So, while vaccination is now less effective at preventing infection, it continues reduces its severity and thus the risk of complications like autoimmunity.

Of course, there may be some even longer-term side effects of viral infections. MS can take decades to be diagnosed after EBV infection. Influenza is associated with a latent risk of Parkinson’s disease; HPV infections can cause cancer as the years and decades roll by.

It will be interesting to see if anything else comes along before the story of Sars CoV-2 is over – not that it ever will be. 


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