DEIR AL-BALAH, Gaza Strip (AP) — Palestinian health authorities and United Nations agencies on Sunday began a large-scale campaign of vaccinations against polio in the Gaza Strip, hoping to prevent an outbreak in the territory that has been ravaged by the ongoing Israel-Hamas war.

Authorities plan to vaccinate children in central Gaza until Wednesday before moving on to the more devastated northern and southern parts of the strip. The campaign began with a small number of vaccinations on Saturday and aims to reach about 640,000 children.

Israel has agreed to limited pauses in fighting to facilitate the campaign, according to the World Health Organization.

Hospitals in Deir al-Balah and Nuseirat confirmed that the campaign had begun on Sunday.