One billionaire could spend 20 billion dollars and vaccinate the entire world, plus found an institution that could watch out for new pandemics and have teeth to deal with it.

Two billionaires could spend 10 billion dollars each and vaccinate the entire world etc.

Five billionaires could spent 4 billion dollars each and vaccinate the world etc.

Why haven't they? If they want to be the superpumped aristocrats they need to understand the concept of "noblesse oblige" - which basically means, if you're extremely rich you should help people.

If you don't do that, the peasants will eventually come for your bunker and burn it to the ground and hang you from the nearest lamp post.

Don't think that's possible? Nor did the French aristos and the Russian aristos.