We had a non-zero chance of stopping covid, even considering vaccines would take a couple of years to get to everyone, it didn't matter (much) if variants happened. The chance of zero covid comes from vaccines coming out fast enough to drop the R value below 1.0 for a significant amount of time for the virus to go away.

However, in hindsight, with animal populations being able to get infected, I think it probably was zero, although that gets well beyond my armchair "skills" ;)