Health workers in Vanuatu are racing to immunise as many children as possible to prevent a measles epidemic.
They fear the conditions left by Cyclone Pam could lead to a nationwide outbreak.
Vaccinations started in earnest on Tuesday with the hope of immunising 10,000 children in the capital, Port Vila, alone.
On the outskirts of Vanuatu's capital, a call goes out by megaphone for children to come out from where they are staying.
Some are staying in their homes, while others are displaced.
This area is poor, and it is well-populated. This is the latest in a string of vaccinations that were only able to start on Tuesday.
A UNICEF immunisation specialist, Ridwan Gustiana, said the cyclone means children have double the risk of getting measles.
"In Port Vila we're targetting to vaccinate 10,000 children between six months and five years old. Yesterday we managed to vaccinate 15,00 and our target today is 1,200," he said.
He is with one of four teams working in the same area at the same time, while two others are slightly further away.
All of them are battling to stop a measles outbreak which he fears could spread across islands, and across the country.
"Everything's collapsed. So now we start trying to reactivate that. We're basically predicting it will possibly increase but hopefully speeding up the vaccinations will reduce the speed and spread of the disease," Mr Gustiana said.
Claudia Shem is one of the many mothers who has brought her young child along the debris-littered streets for vaccination.
Hers is three years old.
"After a disaster, children will always be the most delicate and [get] sick very easily. It is very important for our kids to get vaccinated," she said.
Parents are given general health messages and other items easily handed out like Vitamin A and worming tablets.
Mr Gustiana said that until last year, Vanuatu had for many years been free of measles.
But he said there was an outbreak last year when it was brought from Solomon Islands.
It was contained, but more cases were found in January.
The day starts for the vaccination teams back at Vanuatu's crippled national immunisation storage facility.
They are briefed in the dark about the day ahead - only emergency lighting is working after flooding swept through the building.
Mr Gustiana said what other power there was largely went toward the crucial task of keeping the vaccines cool.
After 48 hours, the vaccines cannot be used.
He feared he wouldn't be able to find a generator in time before they became useless.
"With a disaster people usually gather in one safe place, that's basically how measles spreads very easily. Measles is very dangerous, it can kill children very easily if they get measles," he said.