My wife had her second Pfizer experimental injection last week. (Yes, she's a high-IQ intelligent idiot.) Today I took a small but powerful neodimum magnet and placed it on her arm. It failed to stick. There was no attraction whatsoever.
Oh, and I haven't suffered from any "shedding" symptoms whatsoever.
Just for the record.
I only have anecdotal experience to go by, but a coworker with both moderna shots was able to get the magnet to stick.