A neodymium magnet is among the strongest permanent magnets sold. I would just point out that if there was some
metal-stuff in the vaccine sufficient to stick a magnet to, it would go in, and then disperse in the body. So the experiment we need is for people to do the magnet on both arms immediately after getting the shot, or as short a time as possible.
My bias on this is: hoax. But I am a scientist. My inner scientist says: do the experiments in a controlled way, publish the data.
Lightweight magnets and nonmagnetic objects stuck to the vaccination sites because of the sticky slime oozing out after vaccination. If a person is dirty enough, the light magnets will stick to the forehead, too. People should take baths.