The number of measles cases recorded in the Swansea outbreak - which started last November - has passed 1,000, according to Public Health Wales.
Some 1,011 cases have now been recorded and 9,000 people aged between 10 and 18 still need to be vaccinated.
In the last month, 4,000 people have received the MMR jab.
ITV News Science and Medical Editor Lawrence McGinty reports:
But Public Health Wales has warned that the country as a whole needs to replicate Swansea's response to the outbreak, with 50,000 10 to 18 year-olds still unvaccinated across Wales.
Marion Lyons, director of health protection for Public Health Wales, said: “While not enough children are vaccinated, this outbreak can easily spread anywhere in Wales.”
An ITV News/Com Res poll has found 71% of people think parents are acting irresponsibly if they don't get the MMR jab for their children.