UNICEF aid workers in Vanuatu are aiming to immunise 1000 children a day over the next ten days to prevent a measles epidemic.
Follow our reporters Koroi Hawkins and Kim Baker Wilson LIVE in Port Vila
Relief agencies said conditions following Cyclone Pam are among the most challenging they have faced, with concerns mounting that disease and a lack of clean water could lead to more deaths.
UNICEF spokesperson in Port Vila, Alice Clements, spoke to Radio New Zealand before she flew to Tanna Island this morning.
"So we've already vaccinated 1,000 children under the age of five in the last 24 hours and we're aiming for 10,000 within 10 days."
Ms Clements said the next focus will be getting children back into schools as soon possible, to try reduce their levels of stress with the regular routine of classes.
Disaster management authorities in Vanuatu said the confirmed death toll as a direct result of Cyclone Pam is seven.
They said while the number of fatalities is being reported as 11, technically only seven people were killed by the storm.
They say four sick people died in hospital while the cyclone was battering the country but are included in the toll.
A state of emergency has now been declared for all provinces in Vanuatu.
90 percent of Vanuatu affected
The damage in Vanuatu caused by Cyclone Pam is much worse than previously thought.
Radio New Zealand International reporter Koroi Hawkins said it was originally estimated that 70 percent of the country had been badly damaged by the storm but following an assessment of the outer islands yesterday that's now been scaled up to 90 percent.
He said flying over the capital Port Vila yesterday, the extent of the damage he could see was surreal.
"It was totally devastated, everything like from the coast all the way up to when the hills start in Port Vila is quite a long way. Everything was flattened in one direction, it was like a tsunami type hit without the water."
Aid starts getting through
Emergency aid is beginning to reach some of the worst-hit islands of Vanuatu.
Officials say planes have taken food, water and medical supplies to Tanna island, which was directly in the path of Cyclone Pam.
A United Nations assessor on the island, Joe Lowry, said a huge amount of help will be needed in the coming weeks.
The Red Cross, meanwhile, has started to give personal hygiene kits to cyclone victims.
Spokesperson in Port Vila, Hanna Butler, said the Red Cross had managed to mobilise support from around the world, and the response is going well.
Children's charity UNICEF said it was preparing for what could be an influx of malnourished children at Port Vila's hospital.
Emergency nutrition specialist Megan Gayford said it was expecting the rate of infectious disease to increase.
Forced to dig for spoilt food
Villagers just outside of Port Vila say they are having to dig up crops from under floodwater so they have food to eat.
The chief of Mele Village, Kalokai Masai, said food was starting to becoming an issue but he has faith that aid organisations will help them.
"We have two rivers and the village was in the middle and when we're talking about the flooding, it [destroyed] our gardens and we could not see any crops from the grounds, so we dig where we know there's something there."
His village in Efate is focussing on repairing the school grounds in time for classes next week and recovering crops.
Chief Masai said the community can learn a lot from 1987 Cyclone Uma as they rebuild and recover.
"What we need is we need to cooperate and rebuild in such a way that whatever we find we rebuild in terms of looking into restructuring back our buildings and things. Of course this needs money and things but as a community it will take time."
Police in Port Vila are searching for a person who forced dozens of people to run to the hills in the middle of the night after spreading a false tsunami warning.
Police say that in the absence of any power in Port Vila following Cyclone Pam at the weekend, a vehicle passed through the darkness warning people to get out of their houses because a tsunami was going to hit the capital.
There were reports of injuries as people then rushed to higher ground, before police managed to get the situation under control.