A measles outbreak in West Cork has now affected 51 children, including two who have been hospitalised.
Most of the children infected in Cork are teenagers and 88% of cases have never received any dose of the MMR vaccine.
The HSE is issuing a warning to parents to vaccinate their children against the disease, with the HSE's Assistant National Director of Health Protection, Dr Kevin Kelleher saying parents often under estimated just how dangerous this disease is.