Public Health Wales is urging parents to ensure their children have the second MMR "booster" jab, as four more cases emerge of measles
Two cases have already been confirmed as experts continue to focus on Cwmtawe School, in Port Talbot, where the new cases have been reported.
A vaccination session was held there last week.
Public health officials fear that youngsters in South West Wales could face a new outbreak of measles because hundreds of children are still not fully immunised.
Today they began vaccinating at Cwmtawe school in Pontardawe after one confirmed case and two suspected cases were diagnosed there. A further two cases are suspected at a school at Abercrave, further up the Swansea Valley. Rob Osborne reports.
A vaccination clinic is being held at Cwmtawe School in Pontardawe today after one confirmed and two suspected cases of measles at the school.
A further two cases have are suspected in children at Ysgol Y Cribarth in Powys.
More than 200 children at Cwmtawe are not fully vaccinated.
It is just three months after the end of Wales's biggest ever measles outbreak, which was also centred on the Swansea area.
More than 1,200 people contracted measles, 88 serious enough to visit hospital, and one person died.
In spite of vaccinating more than 75,000 people during the last outbreak, health officials are concerned that at least 30,000 children remain unvaccinated in Wales.
The symptoms of measles include a fever, fatigue, runny nose, pink eyes and a distinctive red rash.
Doctors are urging parents to keep children at home if they suspect measles and to seek medical advice.
They say that any unvaccinated children should receive the MMR jab as soon as possible.
Public Health Wales says there are a further four suspected cases of measles connected with a school in Neath Port Talbot.
Pupils at Cwmtawe School are due to be offered the MMR jab from tomorrow, after one child was confirmed to have measles on Friday.
Public Health Wales say two further suspected cases have been identified in the school and two other cases in Ysgol Y Cribarth, Powys, which are connected to the Neath Port Talbot cases.
Health Minister Mark Drakeford AM says the Welsh Government and local health board are well versed in dealing with measles after the Swansea outbreak. He says they are aiming to 'get on top' of what he described as a 'small outbreak' before it gets any bigger.
Public health officials say a decision will be made today on when more than 200 children in the Neath Port Talbot area will receive MMR vaccinations.
Laboratory tests last week confirmed a child at Cwmtawe Comprehensive School had contracted measles.
Abertawe Bro Morgannwg University Health Board is arranging for MMR vaccinations to be offered this week to all pupils at the school who are not fully vaccinated.
Of 1,260 pupils, 62 are recorded as having received no doses of the MMR vaccine and 142 have received only one dose.
The measles outbreak, centred on Swansea and Neath Port Talbot, earlier this year resulted in more than 1,200 cases - and was officially declared over in July.
MMR vaccinations will be offered to more than 200 children at a Neath Port Talbot secondary school after a case of measles was confirmed in a pupil.
Public Health Wales has received two notifications of measles in pupils at Cwmtawe Comprehensive School and one of these has been laboratory confirmed.
Abertawe Bro Morgannwg University Health Board is arranging for MMR vaccinations to be offered to all pupils at the school who are not fully vaccinated next week.
Of 1,260 pupils at the school, 62 are recorded as having received no doses of the MMR vaccine and 142 have received only one dose.
Two doses of MMR are needed to provide the maximum 99 per cent protection against measles.
Public Health Wales issues the following information on mumps:
- An acute viral illness, only known to affect humans
- Transmitted by direct contact with saliva or droplets from saliva of infected person
- One or both of parotid salivary glands (near ears) swell up and become painful
- Around one-third of people infected develop no symptoms
- Most cases are mild, but when complications occur they can be serious
- Can be caught at any age
- Having it once usually confers lifelong immunity to catching it again
- Measles-mumps-rubella (MMR) immunisation protects over 95% of children
- Current schedule recommends one dose to be given at around 13 months, and a second dose at between 3-5 years
Public Health Wales is warning that there could be an outbreak of mumps here, because too many young people have still not had an MMR vaccination.
In Wales, there have been the following confirmed cases of mumps:
- 76 so far this year, until the end of May
- 88 for the whole of 2012
- 77 for the whole of 2011
More than 50,000 unscheduled MMR vaccinations have been given across Wales since the outbreak of measles began. The public health body says young people between 10 and 18 have been hardest hit by the outbreak - and there are still 35,000 in this age group unvaccinated.
Dr Marion Lyons from Public Health Wales said the outbreak "has slowed significantly, but parents should not believe this is the last we will see of measles in Wales if large numbers remain unvaccinated."