The HSE is currently investigating a confirmed measles disease in Co. Mayo, with close contacts being identified and notified.
The case, which concerns a child, was reported in late April, and anyone who develops symptoms is being urged to stay at home and to phone their GP for advice.
Dr Emer O’Connell, Consultant in Public Health Medicine, said that measles can be a serious illness and is highly infectious.
“One person with the disease can infect 90 per cent of the people around them who have not been immunised,” she said.
“The best protection is to be fully vaccinated with two doses of MMR vaccine.”
Measles symptoms include a temperature of 38 degrees Celsius or above, cold-like symptoms, sore red eyes, rash (which usually appears on the head and neck first and then spreads to the rest of the body), and vomiting, diarrhoea or tummy pain.
The MMR vaccine can prevent measles in over 90% of immunised children, following a single dose of the vaccine.
With the second dose of MMR vaccine, over 99% of immunised children are protected from measles infection.
Those born in Ireland before 1978 or have had measles are unlikely to require vaccination, as they are probably immune.
Children should receive their first dose of MMR vaccine aged 1 and a second dose in baby infants when they are 4 or 5.
There is also a free catch-up MMR option via participating GPs for those who may have missed their vaccination when younger.