The people who are vaccinated are not in the hospital. Of the most sensitive group 84% have been vaccinated.
The number of cases are coming from the younger population which is EXCELLENT news. These people will have natural immunity.
The problem is, "natural immunity", unless one has been recently ill with the disease under discussion, is sort of a "standby mode" whose strength is more or less proportional to the apparent threat of the disease. "Immunity" to cold viruses is usually geared to prevent serious illness, but is not designed to prevent milder cases because those milder cases are only rarely a serious threat. If the body maintained a high level defense to every seemingly (to it) mild virus out there, it (one's body) would be worn out before we hit 15 years old... Sorta like North Korea, 10x.
The specific problem with Delta is that it achieves it's infectiousness by causing "spreaders" to shed many times more virions (some sources claim 1000x!) than the early variants. This means similarly higher viral loads to potential infectees, in most cases, and a high viral load can definitely cause disease and perhaps serious disease, more readily than can a modest viral load. There are, quite simply, more invaders to overrun the body's early defenses and potentially create a serious case.
Recent illness or vaccination usually creates much stronger prevention of serious disease, although sometimes even that can fall short. No vaccine maker claims better than 95% overall efficacy, and that's with "early Covid" types. IMO, even if one allows that vaccinated persons might mitigate better in other ways in addition to vaccination, present efficacy of the current vaccines over 95% "in the field", over all populations, is near impossible, given the likely viral loads now occurring. (This has little to do with what's going on inside any particular hospital.)
It's also true that simple math indicates the 99.9% stated earlier is hyperbole.
OTOH, most people (honest people, anyway) who are able to monitor even loosely a significant size community around them via non-governmental means know COVID to date has been far, far more risky overall than the Covid vacc's with EAU's in the US. Never mind the disastrous health, economic and other effects of incompetent Gov't reaction(s) to Covid.
Ditto if one trusts non-gov't communication from the vast majority of our health care pro's. Conclusion: The numbers spouted by rabid anti-vaccer's are twisted into hyperbole, too.
I say "A plague on both these houses" (or at least a plague on the hyperbole anyway!)