The age at which toddlers receive the MMR triple vaccine in Northern Ireland is to fall to 13 months.
It follows advice from the joint committee on vaccination and immunisation and the latest medical research to bring Northern Ireland into line with the rest of the UK.
Chief medical officer Dr Michael McBride said: "By bringing immunisation forward to 13 months, we can achieve two additional months of protection against measles, mumps and rubella, and still ensure that babies are old enough to respond effectively to this important vaccine."
Dr McBride urged all parents to have their children vaccinated and said measles outbreaks have occurred in Northern Ireland this year.
"This should serve as a reminder to parents that that MMR vaccine is the safest and most effective way to prevent measles, mumps and rubella and that all children should have two doses of MMR vaccine by age four to ensure they are protected," he added.
The change will come into effect from Monday and will be rolled out throughout November and December.