The number of cases in the Swansea measles epidemic has topped the 1,000 mark.
Public Health Wales says the figure now stands at 1,011 but added that about 5,000 youngsters in the area aged between 10 and 18 still need vaccinating.
A vaccination programme has been running in schools and hospitals with 4,000 receiving the MMR jab in the last month alone.
The outbreak started last November.
A total of 84 people have been treated in hospital since it began while a post-mortem examination into the death of a man who died while suffering from measles proved inconclusive.
An inquest into the death of 25-year-old Gareth Colfer-Williams from Swansea was opened and adjourned on Tuesday.
Vaccinations are also continuing in schools in the Abertawe Bro Morgannwg health board area, which covers Swansea, Neath Port Talbot and Bridgend.
Dr Marion Lyons, director of health protection for Public Health Wales, said: "The efforts to vaccinate susceptible children in the Abertawe Bro Morgannwg University Health Board area have been tremendous and we are delighted to see that around half of children needing vaccination have now received the MMR.
"But with around 50,000 children (in Wales) in the 10 to 18 age group still not vaccinated and more than 1,000 cases now reported to us, we cannot be complacent.
"While not enough children are vaccinated, this outbreak can easily spread anywhere in Wales.
"Therefore we urge parents of children, and young people themselves, to take up opportunities to receive the MMR vaccine as a matter of urgency.
"Vaccination sessions are continuing in schools throughout Wales and I urge pupils and their parents to take advantage of these.
"Those not vaccinated are highly likely to catch measles, which is highly contagious.
"It is just a matter of time before a child is left with serious and permanent complications such as eye disorders, deafness or brain damage, or dies."
Hywel Dda Health Board school nursing service is also visiting secondary schools in Carmarthenshire, Pembrokeshire and Ceredigion to offer the vaccine to up to 4,000 pupils who have not yet received the first or both MMR vaccinations.
In England, one million schoolchildren who missed MMR jabs are to be targeted by a vaccination plan aimed at curbing the growing threat of measles.
There are fears that a generation of children have low levels of protection after the MMR scare in the 1990s.
The catch-up campaign, run through GPs, schools and community groups, will focus on children aged 10 to 16.
The campaign is expected to cost £20m and the Department of Health already has 1.2 million vaccines ready to go.
Typical symptoms of measles include fever, cough, conjunctivitis and a rash.
Complications are quite common even in healthy people, and around 20% of reported measles cases experience one or more complication.
These can include ear infections, vomiting and diarrhoea, pneumonia, meningitis and serious eye disorders.