Actually, the vaccination schedules differ from one state to the next, and the 4yo MMR is standard in Victoria.

As I said, I agonised over this decision. The research (aside from the mercury issue) that I read indicated a problem from combining vaccines not only in the same shot (like MMR) but the seperate shots on the same day - we have MMR and 2 other vaccinatins all at once at 12 months.