For me it was the knowledge that whilst cases of serious communicable diseases are rare in Australia now, they are still prevalent in other countries. People travel more than they used to, therefore the chances of these diseases making a comeback if vaccination rates fall is real. Thousands of children still die from complications from things like measles in developing countries because they do not have access to the vaccines we take for granted here.
I spoke at length about risks versus benefits with my dad (a gp) and did lots of research into side effects, and I decided the benefits of vaccines for my child and the community outweigh the possible risks.

I do think adverse reactions need to be better documented though. I delayed the rotavirus vax because of a bad reaction with dd (and the fact different states have different standards and doses).

I think it's clear vaccines work for a large percentage of people. I also think more information needs to be spread about getting vaccines done ASAP, because the idea of delayed vaccination confuses me. Aren't we trying to protect young babies as well? (I am the hypocrite here because I didn't get ds vaccinated according to the schedule).