Israel says it has shipped more than 280,000 vials of the polio vaccine to the Gaza Strip, enough for about 2.8 million doses, since the beginning of its war against Hamas, and on Sunday said it will send 60,000 additional vials into the Palestinian enclave in coming weeks to vaccinate more than one million children. The move comes after the World Health Organization on Friday reported that polio was detected in wastewater samples in July in the Gaza Strip communities of Khan Younis and Deir al Balah.

“Since the discovery of the virus in July, and as part of the vaccination campaign, 9,000 vials were brought through the Kerem Shalom crossing, providing 90,000 additional doses of the vaccine,” Israeli government officials said Sunday on the Telegram social networking site. More than 43,000 vaccine vials, tailored to the virus found in the environmental samples, are expected to soon arrive in Israel and be transported into the Gaza Strip, officials said. “This will be sufficient to vaccinate over one million children in two doses — a total of 2,162,500 doses,” Israeli officials said.

On Friday, U.N. Secretary-General Antonio Guterres said Gaza was in a “humanitarian freefall” and called for a cease-fire so a potential polio outbreak could be averted.

“Just when it seems the situation could not get worse for Palestinians in Gaza, the suffering grows and the world watches,” Mr. Guterres told reporters. “The virus is now circulating, with hundreds of thousands .