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.
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