On Thursday, the United Nations announced a plan to try to address one of the most terrifying consequences of Israel’s U.S.-backed offensive war in the Gaza Strip: the return of the feared poliovirus to the Palestinian territory.

Health experts call the U.N. campaign a hugely important bid to protect hundreds of thousands of children in Gaza and to shield neighboring communities — but they are unsure whether it will work, as fighting between Israel and Gaza-based militant group Hamas continues.

Polio had been wiped out in Gaza as it has in much of the world, with its last case reported 25 years ago. Yet Israel’s military operation, which followed a Hamas-led attack on Israel in October 2023, destroyed the area’s water and medical facilities and forced nearly 2 million people out of their homes. This created conditions in which the virus could flourish.

Earlier this month, local health officials confirmed that a baby had contracted the disease. The child, 11-month-old Abdul Rahman, has become severely weak, his mother recently told CNN; polio cannot be cured and can lead to paralysis or death for children.

Starting Sunday, medical personnel working with the U.N., partner organizations and Gaza’s Health Ministry will attempt to provide polio vaccines to an estimated 640,000 children in the strip who are under the age of 10, said Dr. Rik Peeperkorn of the United Nations’ World Health Organization in a Thursday press conference.

U.N. negotiations with Israeli authorities over the vaccination campaign failed to achieve the goal that aid groups sought: a “polio pause” in combat across Gaza, an idea that Hamas agreed to but was a tougher sell to Israel’s hawkish government. Instead, three-day, area-specific pauses to allow for the safe delivery of vaccinations will occur in different sections of the territory, Peeperkorn said, starting in central Gaza, where Israeli evacuation orders covering other parts of the strip have forced more than an estimated 1 million people onto a tiny piece of land.

For humanitarian workers who have already spent nearly 11 months trying to support people in Gaza, the painful process of reaching a deal was noteworthy in itself given the danger that polio poses.

“It’s really important that people understand the craziness of this, the depravity. Polio’s been almost eradicated in the world,” said Sean Carroll, the CEO of the aid group Anera.

“The idea that we’d be debating whether there’s a cease-fire to deliver polio vaccines … this is crazy,” continued Carroll, a former official at the U.S. Agency for International Development.

The sentiment reflects a concern that aid groups have expressed since the start of the war, particularly in calling for a different approach from Washington, the main sponsor of Israel’s military operation. To a degree not seen in other conflicts, including past Israeli-Palestinian clashes, they say the U.S. and other world powers are missing the forest for the trees. Amid Israel’s sweeping operation, officials are discussing details like how many trucks full of aid enter Gaza or how many days Israel will halt fighting to deliver vaccines instead of big steps that could dramatically ease Palestinian suffering, like Israel restoring electricity to the territory, ceasing its practice of forcing mass displacement, or adopting an immediate cease-fire.

The polio vaccination campaign is focused on children because of how intensely the virus can affect them and because thousands are likely to have not received inoculations since the war began, explained Dr. Zaher Sahloul, the president of the nonprofit MedGlobal, one of the United Nations’ partners in the vaccination effort. Israeli attacks on dozens of hospitals and clinics, restrictions on the flow of medical supplies, and the killing and displacement of health care workers have decimated Gaza’s public health sector, which had previously achieved a 99% polio vaccination rate.

Still, even with a plan in place and vaccines shipped into Gaza, those delivering the inoculations are doing so under intense duress, Sahloul noted, since they are physicians and nurses who are from the communities they are serving and who face the same struggles as their patients to secure shelter, clean water and food.

“Many of them lost family members; their houses are destroyed,” Sahloul added. And he highlighted a worsening problem: the severe lack of cash among Palestinians, which makes it hard for them to purchase even the supplies that are still available in Gaza’s markets. His group pays its staff in the territory via an app called PalPay, linked to the Bank of Palestine. But with the bank’s operations torpedoed in Gaza, Sahloul’s employees’ best hope of translating digital payments into cash is by using so-called exchanges, which often charge a service fee of up to 30% or 40% of the amount they are handling.

“There’s a huge black market and exploitation,” he said.

Meanwhile, the flow of foreign aid workers into Gaza has plummeted in recent months, after Israel’s takeover of the southern town of Rafah led to the closure of the Palestinian enclave’s southern border with Egypt, according to Moureen Kaki, an American aid worker who has been in central Gaza since earlier this summer, working with the organization Glia.

Meanwhile, the continued conflict means continued danger for medical personnel.

The bargain among the U.N., Israel and Hamas-linked officials ostensibly means there will be hours without fighting or bombing in the areas where vaccinations are occurring. And the WHO has developed a deconfliction mechanism with Israel’s military.

But “nothing is guaranteed,” said Mohammed Aghaalkurdi, a member of the group Medical Aid for Palestinians, who noted that at least 500 health care workers have been killed during the war so far.

On Thursday, the Israeli military launched a missile at a humanitarian convoy, killing five transportation workers and claiming armed men had captured one of its vehicles. And on Wednesday, the World Food Programme reported that one of its vehicles was shot at near an Israeli checkpoint in Gaza.

With fears of a polio outbreak still looming for now — and driving concern about large unvaccinated populations in Gaza’s neighbors Israel, Jordan and Egypt — Sahloul called the situation “an international failure.”

“War is the enemy of health,” he added.