For those that want a bit of evidence and scientific background on this, Derek Lowe's writings are, as usual, an excellent source. https://blogs.sciencemag.org/pipeline/archives/2021/03/16/wh... It is a scientifically and statistically rigorous look at the available data that takes into account how people probably feel about the whole issue.
I think this article is a bit more nuanced based on what they are seeing on the ground. Derek brings up good points about background rates, but papers over some things. It's a complex picture and the below article paints it well. Also scientists in Norway claim they found the mechanism that causes it. https://www.sciencemag.org/news/2021/03/it-s-very-special-pi... https://www.vg.no/nyheter/innenriks/i/KyGv2G/professo…
Is there an answer to this yet? The batch that a particular person's dose came from is carefully documented (or at least should be - it is in the USA).