Cwmtawe School measles: 200 to be offered MMR jab
Two hundred pupils at a secondary school in Neath Port Talbot are being offered the MMR vaccination.
Tuesday's special session was organised following one confirmed case of measles and four suspected cases linked to Cwmtawe School in Pontardawe.
Two pupils and a member of staff have been affected by the outbreak, said health officials.
There are two other suspected cases, believed to be relatives who are pupils at another school.
Public health officials said those two probable cases had been identified in children at Ysgol Y Cribarth, Abercrave, Powys.
Parents of children who are not protected against measles but who are showing symptoms, including a fever, runny nose and rash, are being asked to keep their children at home.
Health officials said a disappointing number of children at Cwmtawe had been vaccinated.
Of 1,260 pupils, 62 are recorded as having received no doses of the MMR vaccine and 142 have received only one dose.
But at Ysgol Y Cribarth, the number of unvaccinated children is so small Powys Teaching Health Board is making arrangements for children to be immunised individually.
It comes three months after Wales' biggest measles outbreak ended.
The Swansea area epidemic saw suspected cases first reported last November before it spread to mid and west Wales.
By the time the outbreak was declared over in July, it had resulted in 1,219 notifications of measles cases in the Abertawe Bro Morgannwg, Hywel Dda and Powys health board areas.
Some 88 people visited a hospital due to measles during the outbreak and more than 75,000 were vaccinated throughout Wales.
Gareth Colfer-Williams, 25, from Swansea, died from pneumonia after contracting the virus at the height of the epidemic.
The symptoms of measles include a fever, fatigue, runny nose, conjunctivitis and a distinctive red rash.
Two MMR doses are needed to provide the maximum 99% protection against measles, say experts.