I thought all those magnet photos were obvious hoaxes, but I don't know what to think anymore. How much metal is actually needed for a noticeable magnetic react

I thought all those magnet photos were obvious hoaxes, but I don't know what to think anymore. How much metal is actually needed for a noticeable magnetic reaction in the injection site? "Foreign substance detected in Moderna vaccine in Japan may be metal" https://www.japantimes.co.jp/news/2021/08/27/national/moderna-contamination-metal/ https://www.japantimes.co.jp/news/2021/08/27/national/modern...