But: absence of evidence is not necessarily evidence of absence. The fact that we still haven't found convincing evidence (with the caveat that 'millions of people complain about certain symptoms in my book counts as overwhelming evidence') doesn't mean that such a mechanism doesn't exist. It may merely mean that we are looking in the wrong places, my not be looking in the right way and in general still have a poor understanding of how our bodies really work.

GBS for instance:

https://www.who.int/news-room/fact-sheets/detail/guillain-ba...

Is linked to post viral or post bacterial infections, and even though here too there is a lack of complete understanding at least the symptoms are so clear (up to complete paralysis) that denying it seems pointless. It's also super rare, so there is no incentive to deny it.

But if COVID ends up putting a sizeable percentage of the workforce out of action that may well have serious implications for how we deal with chronic disease and post viral infections. Incidentally: this is one of the possible futures that various experts warned about during the early days of the pandemic, that it would be a decade or more before we would fully understand the impact and that by assuming the post infection consequences would be mild that we may have made a grave mistake.

Fortunately some of the more outrageous possibilities have so far not surfaced, this is one that we can deal with.