Of course since they remain a viable reservoir of the virus, it can and will continue to attempt to expand beyond their borders.
They are a viral cesspool that threatens to infect everyone.
Ok, that was a bit dramatic, but the point is, you can't leave a viable infectious reservoir if you want to eradicate a disease.
Look at smallpox. There was a massive campaign to inoculate everyone on the planet. The got pretty close to that goal, and no area was left untouched. Now, the only smallpox you are going to see are the samples still held by certain organizations. Most of the doctors and scientists want even those samples eradicated, but a few fools have been preventing that for over a decade. (I could list why their excuses are invalid, but this isn't the place.)
They are just trying to do the same thing with polio. This can only be effectively done with diseases that reside exclusively in humans.
Ok, some people are going with the Star Trek Prime Directive excuse. In Next Gen and later, the wimps writing for them interpreted it as a total hands off let them suffer version. In the original series, it was a don't mess with their development kind of thing. Curing a plague was ok, so was evacuating a doomed planet. On the other hand, you don't set yourself up as gods, provide them with advanced tech or science, or force a non-space faring planet into the federation.
In the New stuff, they'd totally let everyone suffer and die, and then wring their hands metaphorically and congratulate themselves on not interfering in the development of another culture.
In the Old stuff, they'd have provided a vaccine and aided in it's distribution and then congratulate themselves on saving vast numbers of peoples lives among the primitive culture, and making it possible for them to continue to develop on their own.
Yes, I watched a lot of Star Trek when I was younger.
One of the problems some people are overlooking is that vaccinations need to go to the people, the people can't really go to the vaccines, or at least not the distances and locations that would be required if they had to go to the major cities. Few people have the kind of transportation necessary, and leaving your own area, ESPECIALLY if you are a tribal, it is an immediate and large risk to your survival and well being. It would be great if the government would provide security escorts for the aid workers, but again, it's not going to work in the boonies out there. Some tribal territories would consider that a hostile act, and either not cooperate, or actually try to kill everyone involved.
As to the CIA thing, I hadn't heard of it, and am somewhat doubtful without further documentation. On the other hand, that's the kind of bullshit the CIA is know for doing, even though I'm pretty sure it's against international law. Even if it isn't against international law, it is a horribly stupid thing to do as it will put all humanitarian aid personnel and projects in jeopardy for years if not decades. It's something no intelligent, rational, or ethical person would do. In other words, right up spy alley.
As to the Taliban, they've already proven they'll say and do anything to force people to follow and obey their power. They have proven themselves to the world to be irrational unreasoning scum of the worst sort. They don't want outsiders in their territories and will happily lie, steal, cheat, and kill to get their way.