Had a good friend whose boyfriend had the J&J Jab. He had some prior issues and had a transplant at one point a few years back. After getting the jab, his body began rejecting the organ. He spent a month in ICU, with doctors telling his girlfriend, my friend, to prepare for the worse. After the month in ICU and continued dialysis, he improved, but it was certainly touch and go there for a while.
Talked to someone at church who is having rejection of her knee and ankle replacements after the jab.