This is not true. Unvaccinated people are catching covid at a significantly faster rate than vaccinated people. So clearly it's stopping some people from getting COVID.
I'm not aware of any particular group of people who would be safer not getting vaccinated than getting vaccinated.
This does not mean there is 0 risk of getting vaccinated, of course. There is no such thing as 0 risk. But all statistical analysis done shows that every single group of people are more likely to die if they don't get vaccinated than if they do get vaccinated.
So, there really isn't a great rational reason to not get vaccinated. For every single person that I'm aware of, getting vaccinated lowers your risk of death or serious disease.