Depends on the vaccine and the illness as to how long they last. All need boosters sooner or later.
Of course people still get admitted, the vaccines reduce severity, nothing more or less. But look at cases and then at admissions and even better, deaths, and you can see clearly how much the vaccines reduce its impact.
I can tell you how many people have died from covid. There are side-effects for some people, I've got the admission numbers somewhere but all the same side effects are seen from covid but worse. That would make sense when you think about it. Not sure about untested: it is essentially still phase 4 but the volumes of people vaccinated are absolutely f*ckin huge compared to what most medicines are tested on. That's what holds most things up, getting enough numbers to be sure. Some people will die from the vaccine to be sure, there's always someone with some odd reaction but at the moment no-one in the patch I have data for has died from the vaccine ... But thousands have died from covid, millions worldwide. The question is which is the smaller risk? The answer to that is absolutely beyond any doubt: you are orders of magnitude more likely to have long term side effects or die from covid over the vaccine. Moreover, it will become endemic so it isn't a case of if you'll get it, only when. Effectively you have no choice, only whether you prime your body first with a vaccine.