The successful eradication of smallpox is indeed a reason to be hopeful. As they say, if we did it once, we might be able to do it again. But smallpox is a DNA virus, unlike SARS-CoV-2 and influenza virus that are RNA viruses. And RNA viruses mutate faster, so I think it might be much more challenging to eradicate SARS-CoV-2 than smallpox.