In the semiconductor industry I have worked with some people who came from the biomedical industry. The two forms of manufacturing have a lot in common and use some of the same types of cleanrooms and protocols. However, they were amazed that we were allowed to keep our own personal notes. Apparently where they came from, all notebooks were serialized and registered, and their notes had to be written in indelible pen, dated, and retained as records. Presumably for legal CYA as well as IP/patent CYA.
There's always the possibility of a big enough conspiracy, but for me I think it's most likely that the vaccines are basically legit. It's still possible there to be longer term or rare side effects that didn't show up in the testing, but it seems unlikely to me, plus, by definition I would be unlikely to experience those.