I don't have much problem with a mandate, but I think you are missing a reason someone might be against one. A vaccine will protect the vast majority of people

I don't have much problem with a mandate, but I think you are missing a reason someone might be against one. A vaccine will protect the vast majority of people from bad outcomes if they themselves get it. There is strengthening evidence that vaccinated people can still be very infectious and a big danger to the unvaccinated. Therefore if you believe that governments should be parsimonious in their regulation of people's activities, mandating a vaccine that doesn't particularly protect anyone but the person who gets it might be an example of government overreach. We let people smoke after all. If you believe that the vaccine will protect others (and I hope it does, despite some recent concerning studies) then it is more defensible to mandate it. Basically, I would hope mandates like this are done on the science instead of on the hope that if we're all very good citizens and get our shots we will somehow be rewarded with protection from the big bad virus and an end to the pandemic.