Some people have no problem modifying their own DNA.

I was watching a video from the YouTube channel Thought Emporium and he took some pills with a virus in them that contained a gene to process lactose in order to inject the gene into the cells lining his intestines to get rid of his lactose intolerance.

Definitely not the kind of thing I would want to do. My DNA is perfectly fine as is and I definitely don't want a vaccine putting extra RNA or DNA in any of my cells.