Forty-five people have been diagnosed with mumps in the west of the country in the last seven weeks.
This has lead to the HSE warning of an outbreak in the region.
In particular, there has been an increase of people aged between 15 and 29 being diagnosed.
For best protection from the viral illness, the HSE is urging those who are unsure if they have received two doses of the MMR vaccination to check immediately.
The viral disease has symptoms often including fever, muscle pain, headache and painful swelling of one or both parotid salivary glands.