Israel’s military and Palestinian group Hamas have agreed to three separate, zoned three-day pauses in fighting in Gaza to allow for the first round of vaccination of 640,000 children against polio, a senior WHO official said on Thursday.

The vaccination campaign is due to start on Sunday, with the pauses scheduled to take place between 6 a.m. and 3 p.m. (0300-1200 GMT), said Rik Peeperkorn, the World Health Organization’s senior official for the Palestinian territories.

He said the campaign would start in central Gaza with three consecutive daily pauses in fighting, then move to southern Gaza, where there would be another three-day pause, followed by northern Gaza. Peeperkorn added there was an agreement to extend the pause in each zone to a fourth day if needed.

“From our experience, we know an additional day or two is very often needed to achieve sufficient coverage,” Mike Ryan, WHO emergencies director, told the U.N. Security Council on Thursday during a meeting on the humanitarian situation in Gaza.

A second round of vaccination would be required four weeks after the first round, said Peeperkorn.

“At least 90% of coverage is needed during each round of the campaign in order to stop the outbreak and prevent international spread of polio,” Ryan said.

The WHO confirmed on Aug. 23 that one baby has been paralyzed by the type 2 polio virus, the first such case in Gaza in 25 years.

“We are ready to cooperate with international organizations to secure this campaign, serving and protecting more than 650,000 Palestinian children in the Gaza Strip,” Hamas official Basem Naim told Reuters.

The Israeli military’s humanitarian unit (COGAT) said on Wednesday that the vaccination campaign would be conducted in coordination with the Israeli military “as part of the routine humanitarian pauses that will allow the population to reach the medical centers where the vaccinations will be administered.”

Evacuation orders

Israel was continuing a “focused and intensive effort” to deliver aid to Gaza and coordinate the polio vaccination campaign with WHO and U.N. children’s agency UNICEF, Oren Marmorstein, spokesperson for Israel’s foreign affairs ministry, posted on X.

Deputy U.S. Ambassador to the U.N. Robert Wood said it was important that Israel facilitate access and “ensure periods of calm and refrain from military operations during vaccination campaign periods.” He added that the United States urged “Israel to avoid further evacuation orders during this period.”

The latest bloodshed in the decades-old Israeli-Palestinian conflict was triggered on Oct. 7 when Palestinian Islamist group Hamas attacked Israel, killing 1,200 and taking about 250 hostages, according to Israeli tallies.

Israel’s subsequent assault on the Hamas-governed enclave has since killed over 40,000 Palestinians, according to the local health ministry, while also displacing nearly the entire population of 2.3 million, causing a hunger crisis and leading to genocide allegations at the World Court that Israel denies.

The U.N. Office for the Coordination of Humanitarian Affairs on Wednesday said aid operations in Gaza were “heavily restricted by hostilities, insecurity, and mass evacuation orders affecting aid transport routes and facilities.”

Acting U.N. aid chief Joyce Msuya said on Thursday that for the first time in the nearly 11-month long war Israel had reversed an evacuation order for three blocks in Deir al-Balah, adding: “Our teams are working to confirm if we can now return to the premises we had to leave on 25 August.”

The evacuation orders issued on Sunday had “led to the largest relocation of U.N. staff since we were forced to leave northern Gaza in October 2023,” Msuya said, affecting some 200 staff, more than a dozen guesthouses used by the U.N. and aid groups and four U.N. warehouses.