Which viral disease has been declared completely eradicated worldwide by vaccination?

Explanation

Smallpox was declared eradicated by the WHO in 1980 after a global vaccination campaign, helped by the fact that the virus had no animal reservoir and every infection was visibly obvious. Polio is the tempting choice because it is close to eradication and Pakistan is one of the last countries still reporting cases, but it is not eradicated. Measles and hepatitis B remain widespread despite effective vaccines.