For smallpox as it existed in his time, perhaps. Remember that it took decades of effort to slowly box in smallpox with widespread vaccinations - and not only have many of those vaccinations worn off, but there are millions upon millions of children and young adults who have never been vaccinated - so any re-eradication process could take months or years.
However, if some idiot genetically engineers new traits into smallpox, then it could be a really nasty bioweapon.
Smallpox was not eradicated with widespread vaccinations. It was eradicated by a very small team that traveled from village to village, vaccinating only those who had been exposed. Once this policy was adopted it took about three years, worldwide.
the mass vaccination policy was a failure.