A major assumption in the 'principle of least harm' on forcing people to get vaccines is that the vaccines are well-characterized in terms of efficacy and side-effects. In the case of the smallpox vaccine, it was a sterilizing vaccine (i.e. there were zero breakthrough cases post-vaccination as far as I know, so it could be used to effectively eliminate the virus from human populations), and the side-effects, though quite severe in some cases (far more than anything reported with Covid vaccines as far as I know), were well-characterized. For example:

Inoculation with vaccinia virus is highly effective for the prevention of smallpox infection, but it is associated with several known side effects that range from mild and self-limited to severe and life-threatening.

(2003) "Smallpox Vaccine: The Good, the Bad, and the Ugly"

http://www.clinmedres.org/content/1/2/87.short

The Covid vaccines are uniformly non-sterilizing, i.e. breakthrough cases are common, even apparently the norm (this may be due to rapid evolution of new virus strains relative to older clinical trials) and the side effects seem to be relatively poorly characterized (heart issues with young adults? fact or fiction?). Hence, glowing stories like this Nov 2020 report on the Moderna vaccine might need some reconsideration:

https://www.science.org/content/article/absolutely-remarkabl...

One could argue, at this point, that a Covid vaccination is really only net beneficial to the elderly, obese and immunocompromised (comparable arguments have been made for the influenza vaccine). One could also argue that for-profit pharmaceutical corporations (who have refused to release patent rights to other manufacturers, which would drive down costs) have large conflicts of interest relative to their desire to maximize profits by pushing vaccination on those for whom it serves no beneficial purpose.