I may have misspoke when I said "bad" flu-like symptoms: they were on par with symptoms from the flu, not relatively worse (although, unpleasant), and they were all expected side effects and began the night I got the vaccine. The several months of lethargy accompanied with random pains was the unexpected part.

I was quarantining at the time and hadn't gone anywhere except the place where I got the vaccine. It would be ironic if I wound up getting COVID there, which lengthened and intensified my side effects. I hadn't considered that before.