It's a fair question. Part of the answer is this: (1) the diseases against which vaccines have historically been mandated are substantially more severe than COVID-19, which is almost unnoticeable except for a very small minority, for whom it can be severe or fatal, (2) the vaccines have been heavily tested and have a very, very low serious side effect ratio compared to their efficacy against the disease to which they provide immunity, and (3) the immunity these vaccines provide does not fade after several months, and is substantially greater with respect to any potential variants within the virus against which they provide immunity, something that the COVID-19 vaccines currently cannot do.
Bring us a COVID-19 vaccine that satisfies the same criteria that these vaccines satisfy, and we can reconsider the issue. Until then, it should remain a matter of personal choice.