A further four cases of measles have been detected in Limerick, bringing the number of people in the city who have contracted the virus to 19 since the beginning of the year.
There is also a case in Dublin linked to the outbreak.
Nine cases involve children aged from newborns to five years and all were not vaccinated. Four of those children had to be admitted to hospital.
Eleven cases were young adults and older individuals aged between 15 and 34, and four had to be admitted to hospital. Only two of the cases in this age group had had the measles, mumps and rubella (MMR) vaccination.
The Health Service Executive said it is holding another MMR vaccination clinic in Limerick city next week to encourage parents of young children who have not had vaccinations to get their children vaccinated, as they say it offers the best protection.
The vaccination clinic will be held on 5 March from 10am at the Barrack View Primary Care Centre in the city's Edward Street.
The symptoms of the illness are a rash, a high fever, a cough and runny nose.
Measles can be life-threatening in very young babies as it may lead to a swelling of the brain, and children will need to be admitted to hospital
The outbreak was first noticed at the beginning of January when three cases were identified, mainly in people from the Carew Park area of Southill and the Ballinacurra Weston area.
An outbreak control team made up of HSE personnel has been established to try to prevent further spread of the illness.
This was carried out by the control team following up on confirmed and suspected cases and their contacts, to ensure they get the vaccine.