The vaccines, which were released from global emergency stockpiles, have already arrived in Gaza and are due to be issued to 640,000 children under 10 years of age.
OCHA said more than 80 per cent of the Gaza Strip is now assessed as having been placed under evacuation orders since the conflict began last October.
While the disease can be effectively prevented through vaccines, a heavily damaged and severely depleted healthcare system in Gaza means that children have not received crucial inoculations.
WHO explained that poliovirus can emerge in areas where poor vaccination coverage allows the weakened form of the orally taken vaccine virus strain to mutate into a stronger version.
It said military activity would be paused from 0500 GMT until 1600 GMT daily until further notice along the road that leads from the Kerem Shalom Crossing to the Salah al-Din Road and then northwards.