Welsh Health Minister Mark Drakeford has said the number of measles cases in the Swansea area will continue to rise in the coming weeks.
In a statement to AMs, Professor Drakeford also said more than 5,000 children in the Swansea area are still at risk from the virus.
He said: “Since that time, measles cases continue to be reported across Wales, with the majority in Abertawe Bro Morgannwg, Powys and Hywel Dda Health Board areas.
On April 11, Public Health Wales reported 693 cases in the outbreak centred on the Swansea area. With the number of cases still increasing daily, the Welsh Government remains concerned and is aware that this outbreak is yet to reach its peak. Indeed, we can fully expect cases to continue to occur for a number of weeks yet.
“The only way to halt the outbreak is to ensure as many people as possible have the MMR vaccine to protect themselves, their children, family members and others in the community who may not be protected for a variety of reasons. Increasing levels of immunisation through MMR vaccination will give the community protection from a potentially dangerous but very preventable disease.”
He added: “We are actively working (along with the media) to raise public awareness of the importance of MMR vaccination and to reiterate the actions that people can take to help themselves and others.”
On the weekend, 563 people were immunised at an MMR clinic held at Ysbyty Ystrad Fawr.
Aneurin Bevan Health Board has said that 34 cases of measles have been reported in its area between January and April.
Public Health Wales figures have revealed that 9,000 children aged five to 18 are not fully protected against measles in the Aneurin Bevan Health Board area.
People who have had two doses of the MMR will be 99% protected against the disease.
An extremely contagious virus, measles can lead to serious complications and in rare cases can be fatal.
The health board has said it is keen to vaccinate people in the 16 to 25 age group and that it is crucial they are vaccinated before exams.
Typical symptoms of measles include fever, cough, conjunctivitis and a rash.
Complications are quite common even in healthy people, and about 20% of reported measles cases experience one or more complications.