Health workers were set to launch a vaccination drive to ward off a feared outbreak of polio in Gaza after Israel and the Hamas terror group both agreed to partially pause fighting for days at a time in parts of the Strip, the World Health Organization said Thursday.

The WHO and UN children’s fund UNICEF are hoping to provide oral vaccines against type 2 poliovirus (cVDPV2) to more than 640,000 children in the Strip after a baby contracted the first confirmed case in 25 years in the Palestinian territory.

Experts say without a vaccination drive, and pauses in the fighting to facilitate the campaign, an outbreak could erupt, sinking the enclave’s civilian population into further misery after months of war.

Described as “humanitarian pauses” that will last three days in different areas of the war-ravaged territory, the vaccination campaign will start Sunday in central Gaza, said Rik Peeperkorn, World Health Organization representative in the Palestinian territories.

That will be followed by another three-day pause in southern Gaza and then another in northern Gaza.

Aid groups had said seven-day pauses were needed at a minimum.

“I’m not going to say this is the ideal way forward. But this is a workable way forward,” Peeperkorn said of the humanitarian pauses, which he said were coordinated with Israeli authorities.

“It will happen and should happen because we have an agreement,” he added.

There was no immediate comment from the office of Prime Minister Benjamin Netanyahu. On Wednesday night, Netanyahu’s office rejected a report that it had agreed to a truce, but said it was “designating certain areas in the Strip” for pauses.

According to the Channel 13 report, the decision was made by Netanyahu and senior defense officials following heavy pressure from US Secretary of State Antony Blinken during a visit to the region last week.

A spokesman for Hamas, which has long sought a halt in hostilities to regroup after nearly 11 months of intense warfare in the Strip, told London-based news site Al-Araby Al-Jadeed Thursday the group had agreed to what it described as a seven-day humanitarian truce.

Jihad Taha told the outlet that Israel must not be allowed to “evade or procrastinate and put in place alternatives by specifying places to start the vaccination process and not committing to any humanitarian truce.”

Egyptian sources cited by the outlet said the truce would not cover areas where the Israel Defense Forces are operating.

The IDF did not immediately comment. Amid the war, the military has frequently announced “tactical pauses” in military activity in certain areas to enable the delivery and distribution of humanitarian aid.

The agreement is independent of any possible ceasefire and hostage release deal being negotiated indirectly between Israel and Hamas.

The IDF said Sunday that vaccines for more than 1 million people had been delivered to Gaza, days after the WHO said a 10-month-old baby had been paralyzed in the lower part of one leg by the type 2 poliovirus, the first such case in the territory in 25 years.

The IDF said at the time that vaccinations would be conducted by international and local medical teams at “various locations” in Gaza, in coordination with Israel’s military as part of “routine humanitarian pauses” to allow people to reach health centers.

Other polio cases are suspected across the largely devastated territory after the virus was detected in wastewater in six different locations in July.

The European Union on Thursday joined the calls for “immediate” humanitarian pauses to facilitate the polio vaccination push.

“Commitment to the humanitarian pauses by all parties will be crucial to allow the successful and timely implementation of these urgent campaigns,” the EU’s top diplomat Josep Borrell said on behalf of the 27-country bloc in a statement.

“An epidemic among a population already weakened by over 10 months of fighting and displacement, malnourishment, lack of basic health services, and deplorable sanitary conditions, as well as further spread internationally, must be avoided,” he said.

The polio strain threatening Gaza evolved from a weakened virus that was originally part of an oral vaccine credited with preventing millions of children worldwide from being paralyzed. But that virus was removed from the vaccine in 2016 in hopes of preventing vaccine-derived outbreaks.

Public health authorities knew that the WHO decision would leave people unprotected against that particular strain, but they thought they had a plan to ward off and quickly contain any outbreaks. Instead, the move resulted in polio outbreaks in 43 countries that paralyzed more than 3,300 children, according to a draft report by experts commissioned by the WHO.

The WHO estimates that 95 percent of the population needs to be immunized against polio to stop outbreaks. Before the war, 99% of Gaza’s population was vaccinated against polio, but that figure is now at 86%, according to the WHO.

While short of a full ceasefire sought by much of the international community, a partial truce would still provide relief to some Gazans who have endured almost a year of fighting in the Palestinian territory, since Israel launched its war to topple Hamas following the October 7 massacres.

Some 1,200 people were killed in the unprecedented attack on Israel and 251 were kidnapped into Gaza. Israel says over 100 hostages remain in Gaza, many of them no longer alive.

US National Security Adviser Jake Sullivan told reporters earlier Thursday that the negotiations for a ceasefire and the release of hostages had made progress.

“The negotiators are bearing down on the details, meaning that we have advanced the discussions to a point where it’s in the nitty-gritty, and that is a positive sign of progress,” he said from Beijing.

Officials from the United States, Egypt, Qatar and Israel have held several days of talks trying to hammer out an updated proposal that could be submitted to Hamas. But there has been no sign of a breakthrough, and Israel and Hamas remain far apart on key issues.

US officials have said they are closing in on a deal, while Hamas has accused the US of adopting unacceptable demands by Israel and trying to force them on the terror group. Officials in Egypt, one of the key mediators, have also expressed skepticism.

“At the end of the day, nothing is done until it’s done. And so we’re just going to keep working at this until we finally get the ceasefire and hostage deal across the line,” Sullivan said.

Israel’s offensive in Gaza has killed over 40,000 people, according to Hamas-controlled health officials, without differentiating between civilians and combatants. Israel says it has killed some 17,000 fighters in battle and another 1,000 terrorists inside Israel on October 7. The figures from both sides cannot be verified.