It's a bit more complex than that. The Smallpox vaccine was based on the virus of another species. The Polio virus is based on a weakened human virus - which, unfortunately, sometimes becomes infectious again and that is a problem in its own right. Also, the last pockets of infection are basically in war zones where it's difficult to get the vaccines to. But hopefully you're right - maybe we'll eradicate it in the next few decades.

OPV is a weakened virus, that's why you took it orally, but the modern vaccine isn't, it's a conventional killed virus vaccine and, since it's dead, can't cause polio.

Unfortunately the modern vaccine is also much more expensive (which is a problem in poor countries) and much less effective (which is a problem in countries with endemic polio).

I thought viruses weren't alive as such?

Sure, and neither is a car. But we understand if someone says "My car is dead" they don't mean merely that they switched off the ignition.

If you prefer another word is "inactivated".

Anyhow, I'd like a more precise description of the difference between "weakened" and "dead/inactive" (which is what the parent of my comment was about).

"bricked"

Viruses being alive is a debated topic and doesn’t have an objective distinction from what I understand.

There are two polio vaccines - the conventional live-attenuated polio vaccine works really well in developing settings, because it's cheap, multi-dose, and vaccinated individuals shed virus, which give people who were previously or un-vaccinated some protection via exposure.

But if we ever get down to actually thinking "These are the last 5 cases..." it's entirely possible to use the killed virus formulation used in the U.S. and Europe.

Where those cases are is a bigger pain.