The United Nations, in collaboration with Palestinian health authorities, began to vaccinate 640,000 children in the Gaza Strip on Sunday, with Israel and Hamas agreeing to brief pauses in their 11-month war to allow the campaign to go ahead.
The World Health Organisation (WHO) confirmed last month that a baby was partially paralysed by the type 2 polio virus, the first such case in the territory in 25 years.
The campaign began on Sunday in areas of central Gaza, and will move to other areas in coming days.