There have been another five deaths in Samoa's measles epidemic, bringing the toll to 53.

It's the sixth day the death toll has risen, with children under the age of four making up almost all but five of the dead.

The Ministry of Health said in the past 24 hours, there were another 198 cases of measles recorded, bringing the total to more than 3700.

One hundred and eighty-three people remain in hospital, including 19 critically ill children.

Samoa is racing to immunise its entire population and today authorities expanded the ages of those eligible for vaccinations.

They're now available for people aged six months to 60 years old.

Breaking: FIVE more children in Samoa have died, the measles death toll at 53. Total cases over 3,700 with 198 new cases overnight.

Just spoke to Fala'i and Lupino who lost little Soane. They're grieving & said the most beautiful things & made us cry too. #SamoaMeasles

— Alex Perrottet (@alexperro) December 2, 2019

Previously, the vaccines were being prioritised for everyone between six months and 19, and non-pregnant women up to 35 years old.

Researchers at the University of Auckland last week developed a model that predicted the epidemic would hit a peak of around 70 deaths.

The assessment is consistent with officials and medical experts who have warned the worst is yet to come.

The researchers' model predicted a total of 4500 to 6500 cases in Samoa.