The number of children who have been vaccinated against illnesses such as measles is well below the national target, according to the chairman of the Regional Vaccination Committee in the north-east.
Dr Peter Finnegan said Irish people have become more complacent about vaccines, and no longer see diseases like mumps or measles as a threat.
About 80% of children are being immunised but Dr Finnegan said if this level should drop, the population may become vulnerable.
On the contrary, if 95% of people were vaccinated, it would be impossible for such diseases to spread, and the risk of an epidemic would diminish, according to Dr Finnegan.