Well, "can" is debatable. The only one we've effectively eradicated is smallpox and that was almost 50 years ago. Of course we couldn't actually eradicate it, though, and kept samples for "research purposes".
Well also Rinderpest, but i suppose you meant human disease.
Personally i'd call smallpox as actually eradicated despite the samples. I think its fair to call other diseases effectively eradicated, even if they aren't total. If less than 10 people in the world are dying per year, that is effective eradication even if not total
Well, it's complicated. As I understand, one of the polio vaccines - the oral one - has an unusual quirk.
The live virus used in it can reproduce and spread in low-vaccination communities. While the vaccine version of it will not cause paralysis, it can and occasionally does mutate back into a pathogenic variant.
So we're sort of maintaining a reservoir of polio, really.
Hopefully though we will slowly wean off the live vaccine. For the most part the live vaccine is only used in developing countries. There are a bunch of factors that make that difficult but i think eventually we will get there.
After eradicating polio for decades, we saw a case for the first time in 2022. https://pmc.ncbi.nlm.nih.gov/articles/PMC9577438/
And given the drop in rates of immunization post covid, we can very expect more if the trend continues.