HSE reiterated the warning to parents in the west after increasing the number of cases of mumps in the region in recent weeks.
Parents of students at Claregalway School are informed that many children have developed mumps-like symptoms.
This is followed by an increase in the number of cases in the area, especially among those aged 15 to 29 years.
HSE says immunization of MMR provides the best protection for people and invites those who have not yet had two doses of the vaccine to find an additional dose.
People who are uncertain, if they have two doses, are also advised to vaccinate as soon as possible, as it can take up to 28 days for the antibodies to get effective.
Children who develop symptoms should be kept outside the school for at least five days after the onset of swelling of the neck.
Public health officials say children may be infected before infusion of swelling and may have additional symptoms such as throat pain, coughing or general malaise.
Mumps spread by coughing and sneezing and can also be transmitted by direct contact with saliva.
It is an acute viral disease, with symptoms including fever, headache and sore swollen swollen glands.
Mumps can also cause complications, such as meningitis, and can cause swollen testicles, which can cause fertility problems in later life.