Updated 21 December 2012, 9:39 AEST
The United Nations Children's Fund has begun helping the children in need in cyclone-affected Fiji and Samoa.
UNICEF says one of the immediate challenges is to ensure there are no outbreaks of disease as a result of contaminated water.
The organisation says it will supply 5,000 doses of tetanus vaccine for Samoa.
It will also provide tens of thousands of sachets of oral rehydration salts to both countries.
UNICEF's representative Dr Isiye Ndombi is in Fiji and says there are several priorities - and challenges.
"Our lead role is in the areas of water, sanitation and nutrition of children and protecting them from harm. Luckily, the schools are closed now," he told Radio Australia's Pacific Beat.
"The immediate priorities are to ensure that these people have sufficient food, they have safe water and sanitation and they have good shelter, but also to circulate key hygiene and health messages to the population.
"Because this is a time when epidemics can spread very easily."
More than 8,000 people in Fiji and 7,000 in Samoa have been forced to flee their homes in the wake of Tropical Cyclone Evan.
UNICEF says water and electricity shortages across both countries are creating a potentially dangerous situation for thousands.
Meanwhile, police in Fiji say 15 people are due in court on Friday charged with looting during Cyclone Evan.
They say 12 men and two women are accused of stealing $20,000 Fijian dollars worth of goods from a supermarket. Another man is accused of stealing $2,000 worth of liquor.
In Samoa, five people have been killed and at least 12 people are still missing after Cyclone Evan smashed into the Pacific island nation last week.
Audio: UNICEF reaching out to children in Fiji, Samoa (ABC News)