Urgent action is needed so children in Wales are fully vaccinated for measles, the chief medical officer has warned.
Sir Frank Atherton said outbreaks could become more frequent unless uptake of the measles, mumps and rubella (MMR) vaccine increased.
He said parents should arrange jabs as soon as possible if their children are not fully vaccinated.
The World Health Organization says 95% should be double vaccinated by the age of five but the UK is below the target.
Latest figures suggest 89.5% of five-year-old children in Wales have had both doses.
Across the UK, the figure is 84.5% - the lowest level since 2010-11.
In recent months, outbreaks of the infection have been reported across the UK in areas including Cardiff and Birmingham.
In January, Birmingham Children's Hospital reported being inundated with its highest number of cases in decades.
The highly infectious disease can spread very quickly among the unvaccinated, especially in settings like nurseries and schools.
Health boards in Wales have now been asked to target pupils in every school to boost immunisation levels.
