To be fair, I can not think of any that have been universally fixed. Even polio is still around in pockets. We have made vast improvements in first world countries but, really, what have we actually fixed? By fixed I mean completely... I honestly can not think of any problems that have been fixed completely. Not a single one that I can not find a case where it is there is still a problem for some portion of the population. Maybe fire but, then again, we can not effectively control it in all instances.
I know I am being pedantic but, frankly, this is one of those subjects where we should be pedantic. Niggling details that affect others besides ourselves are still niggling details with great importance to others, maybe.