CRISIS measures are being introduced as the measles epidemic sweeping Swansea threatens to escalate with the start of the Easter holiday.
Health chiefs are worried that having thousands of children out and about in crowded places could lead to yet more cases being reported — with the risk of a fatality increasingly becoming a statistical inevitability.
Abertawe Bro Morgannwg University Health Board is planning a community-based MMR vaccination programme offering immunisation sessions in places like schools and hospitals.
At the start of this week there were 432 cases across the ABMU board area, the vast majority of them in Swansea with some in Neath Port Talbot and a few in Bridgend.
This figure has more than doubled since March 4, when it stood at just over 200, with 116 cases reported in the past week alone and 51 people — many of them babies — hospitalised.
An ABMU spokeswoman said: "The school holidays have started and parents will no doubt be taking their children to places like leisure centres and cinemas.
"That means a large number of children will be in crowds in relatively confined spaces, rather than just being exposed to pupils in their school or their circle of friends outside school.
"There is a danger, therefore, that the school holidays will not help what is already a very serious situation."
Children need two MMR jabs to ensure maximum protection, one just after their first birthday and the second shortly after their third.
Babies up to the age of one are deemed particularly at risk as they cannot have MMR.
For them to be protected there needs to be so-called herd immunity, where there is sufficient protection among the wider population.
But this requires a 95 per cent take-up of MMR and the ABMU area has only achieved around 75 per cent.
Measles can lead to serious problems such as blindness, deafness, encephalitis and pneumonia, and in some cases can prove fatal.
During an outbreak in Dublin a few years back there were 1,500 cases reported and three deaths.
"Our numbers are now multiplying so quickly there are concerns that, if you look at the statistics, what happened in Ireland could happen here and there could be a death," said the spokeswoman.
She said plans were being put in place to hold community immunisation sessions in places like schools and hospitals.
In the meantime public health officials are urging people to ensure their children have the MMR vaccine even if they think they have already been exposed to the virus.
"The incubation period is 9 to 18 days," said the spokeswoman. "Having MMR could outpace the virus and stop symptoms developing or reduce their severity."