[daanlo]

This very rare side effect, typically happens in the first 2-3 weeks after the vaccination. Src (in German): https://www.rki.de/DE/Content/Infekt/Impfen/Materialien/Down...

Symptoms of the thrombosis include: extreme headaches and/or bruises (without actually hurting yourself).

Src: my (potentially inaccurate) recollection of my doctor telling me about this.

[wincy]

I had the worst headache of my life a few days after getting the J&J vaccine, and went to the emergency room because my wife was worried I’d had Ana aneurysm or something. The ER visit happened the day before the news broke about blood clots and whatnot. The doctor told me it was absolutely unrelated to the vaccine. They did a scan with some contrast dye, said everything looked fine, and discharged me. I couldn’t do strenuous activity for over a week because I’d feel the headache again, almost like a part of the inside of my skull had been scraped, I don’t know how else to describe it.