> (a) I always thought COVID anti-measures including vaccinations are not about death rates but mainly about the "flattening the curve" and protecting our health systems from collapsing, which would result in many more deaths.

What do you mean? In the absence of vaccines or any reason to believe that a vastly more effective treatment would arrive, masks and lockdowns “flatten the curve” in the sense that they primarily defer disease, not prevent it. (Major exception: if lockdowns actually eradicated COVID, it would be all over. A few countries pulled this off, but this is only a long term solution if it worked everywhere.)

Vaccines, however, assuming they work as well as the measles vaccine, prevent deaths outright. Vaccinate 5% of the population and you will reduce the eventual number of severe disease cases and deaths (and long COVID?) by something around 5%. (Maybe more like 2.5% if efficacy is on the low end.). Vaccinate 95% of the population and COVID will resemble measles: a few localized outbreaks will still occur, but most people will never be exposed, let alone get sick.