Actualy, the difference is that if everyone had to get the vaccine, it would/could wipe out the disease. Now, I'm not saying that is the case with this particular disease and vaccines, but that is a huge part of the logic behind a mandatory vaccine, no?
Look, if there were a 100% fatal disease out there, that 10% of the world is going to get (and that is obvious), plus there is a vaccine for this disease that is 50% effective at saving lives and 50% effective at reducing transmission, would you argue that it should be mandatory?
What if those numbers were 100% for all? 100% fatal (unless you're vaccinated), and everyone will get it? Then would you say it should be mandatory? The alternative is that people are choosing suicide.