Question

Long Covid seems to have a lot of symptoms in common with ME/CFS and I know that the MEA has been pointing this out since it soon became apparent that some people were not returning to normal health after catching Covid-19.

One of the important differences between Long Covid and ME/CFS appears to be how people with both conditions react to vaccinations. Those with ME/CFS often report an exacerbation of ME/CFS symptoms and this can sometimes be quite severe and persistent. But there are now numerous reports about people with Long Covid feeling a lot better after having a Covid-19 vaccination and in some cases even recovering from Long Covid. Do we know why this is occurring? And could it have any implications for ME/CFS?

Answer

This is a very interesting and important observation.

The simple answer is that we just don’t know why some people with Long Covid are reporting positive reactions to the Covid vaccines. Among the theories that have been put forward are that the vaccine is eliminating persisting pockets of virus, or viral fragments, in tissue. However, the evidence for persisting viral infection in Long Covid isn’t very strong. Another possible explanation is that a vaccine is ‘resetting’ an abnormal over-reactive response to the triggering infection by the body’s immune system. This abnormal immune system response also seems to occur in ME/CFS when the trigger is an infection.

Vaccinations occasionally act as triggers for the development of ME/CFS – which is not surprising given the fact that vaccines work by mimicking the action of an infection on the body’s immune system in order to produce protective antibodies against a specific infection. And infections are the commonest trigger factor for ME/CFS. When it comes to pre-existing ME/CFS, a significant number of people report that vaccinations cause an exacerbation or relapse of symptoms. We do receive occasional reports of people with ME/CFS improving or feeling a lot better after their Flu vaccination and we've heard of some who felt better after their Covid vaccination, but these improvements are often short-lived and don't seem to effect many people.

It’s possible that this improvement is occurring because it involves a vaccination against the infection that caused Long Covid. It is, of course, very unusual for people with ME/CFS to be vaccinated against the infection that triggered their ME/CFS. We will continue to follow this research with interest. If it does turn out that the Covid-19 vaccines are a way of treating Long Covid, possibly by ‘resetting the immune system’, we will have to explore whether some sort of similar immune system challenge could also be effective in ME/CFS. Once we know for certain that vaccinations are having a beneficial effect in Long Covid, and we understand the reasons why, it could have implications for the treatment of ME/CFS.

• Please let us know if you have experienced a significant improvement in ME/CFS symptoms following a vaccination, and which vaccine it was: feedback@meassociation.org.uk

More information

• Covid-19: Long Covid & ME/CFS
  An extensive free booklet that reviews the overlaps between Long Covid and ME/CFS, and explains how people with Long Covid can safely learn to manage their symptoms and any continuing disability.
• Covid-19: Vaccines & ME/CFS
  In this free leaflet, we tell you all you need to know about the Covid vaccines if you have ME/CFS. It will help should you be struggling to reach a decision about whether to have the vaccinations or not.
• Long Covid and ME/CFS – Are they the same?
  An extensive free booklet that reviews the overlaps between Long Covid and ME/CFS, and explains how people with Long Covid can safely learn to manage their symptoms and any continuing disability.
• Template: Covid-19 ME/CFS Clinically Vulnerable Status 
  This free template letter explains why people with ME/CFS are more vulnerable and should receive extra help in relation to COVID-19.