The Health Ministry is extending its campaign to boost immunisation against measles to those aged between 13 and 20.
More than 220 cases of measles have been notified to the ministry so far this year, over 18 times the total for all of last year.
The ministry says its drive to boost immunisation rates among those aged between one and 12 may be slowing the spread of the illness, and it's time to take the next step towards averting a national epidemic.
Pat Tuohy, chief advisor for child and youth health, says doctors and nurses have been actively recalling children due for a vaccine, and "opportunistically" vaccinating others seeing their doctor.
Immunisation rates appear to have lifted markedly among the younger age group, the ministry says, and the number doses of vaccine given has risen by 70%.
It is now advising those aged between 13 and 20 to be immunised if they haven't had measles or the vaccine, or are unsure whether they're protected.