Polio vaccinations wrap up in Gaza as officials try to inoculate 90% of children under age 10

The last day of the polio vaccination campaign is wrapping up in Gaza, the World Health Organization (WHO) said Thursday.

The campaign was launched after the first case of polio in Gaza in more than 25 years was recently detected. Health officials from the WHO, the Hamas-run Gaza Ministry of Health and partner organizations said they would be vaccinating children in three-day phases starting in central Gaza, then in southern Gaza, and ending in the north.

As of Thursday morning, more than 552,000 children under age 10 out of 640,000 have been vaccinated in Gaza, according to the WHO. The organization said at least 90% coverage is needed to stop a potential outbreak in Gaza, and the campaign may be extended if that 90% figure isn't achieved on Thursday.

Poliovirus was first detected in sewage samples from the cities of Deir al-Balah and Khan Younis – in central and southern Gaza, respectively – in mid-July, in tests conducted by the Gaza Ministry of Health in coordination with the UN.

In mid-August, the Ministry of Health reported the first case of polio in Gaza in 25 years, in a 10-month-old child who had not been vaccinated. Doctors suspected polio after symptoms resembled the virus, which was confirmed in test conducted in Amman, the capital of Jordan, according to the WHO.

Children are receiving two drops of novel oral polio vaccine type 2 (nOPV2), which has been used for outbreak response under the WHO's Emergency Use Listing approval since March 2021. A second dose is typically given four weeks after the first.

"We want to protect our children from diseases and give them the necessary vaccines because prevention is better than cure," Islam Saleh, a mother in northern Gaza, said in a video issued by the United Nations (UN) on Wednesday.

"I fear for my son because there is no cure for polio. This dose he received will protect him, and it is safe," Saleh added.

Officials have said that the vaccination operation is complicated by access restrictions, evacuation orders and fuel shortages. Israel has agreed to "temporary" pauses in fighting each day in order for the vaccinations to be administered.

Earlier this week, a convoy of UN vehicles in northern Gaza was stopped and questioned by Israeli Security Forces before being released, the Israel Defense Forces (IDF) said in a statement.

Polio largely affects children under age 5 and can lead to paralysis or death. According to the Palestinian Central Bureau of Statistics, there are about 341,000 children under the age of five in Gaza.

Children in the U.S. are recommended to get the inactivated polio vaccine as part of routine childhood immunization, according to the Centers for Disease Control and Prevention (CDC). It consists of four doses in total administered first at 2 months of age, then at 4 months, 6-18 months, and 4-6 years.

"It has been heartening to see the response to the campaign," the WHO said in comments released after a press briefing on Thursday. "Everywhere the team has gone, parents are doing all they can to ensure their child does not miss vaccination. Many vaccination sites received more than expected crowds. Special coordinated missions were also conducted to reach children in insecure and heard to reach areas."

ABC News' Jordana Miller and Dana Savir contributed to this report.