Yes. There is a small risk when being immunized. So it might seem safer not to have it done. The risk of catching something is very small because other people are immunized. However the more people that are not immunized the greater the risk to those people. If those other people were not immunized the risk of not being immunized would be much greater.
So basically it is only safer not to be immunized if other people take the risk and are immunized. As a result I think it should be compulsory.