Polio is supposed to be cured. They have a vaccination to prevent it. There has not been many new cases I believe, at least in this part of the world.

But I have friends from my childhood, who are still damaged from the disease, that they got as a child or teenager. Some in iron lung machines died.

Then we have the Post-Polio Syndrome. So when is a cure really considered a cure?

They never did find a definite cause for the Polio in these people, and they never really took away their past damage or treated it.

So there is really no answer to be found in the words, "What would it take?"

To me it would mean:
When MS is wiped off the map of the world, a disease of the past 21 centuries, that no longer exists in the world of the 22nd century perhaps?

MS has been around so long now, probably since time began, people died young back then, before they got any full disease, or a name for it. Until Charcot.

There is not enough research, not enough treatments with a safety factor, the cause and cure are yet to be found. We are only covering a huge wound with a Band-Aid, IMO.