Libertarians would tell you that they have complete sovereignty over their bodies, lives etc, and that the "initiation of force" is the standard by which we know whether or not something is evil.
So, if you had to force a libertarian to be quarantined or to receive a vaccination that may result in them actually contracting the disease (small pox vaccine, like polio vaccine, actually has a small chance of infecting you with the disease and permanently damaging your health), this would be an "initiation of force", would it not?