GENEVA, Switzerland (AFP) — The World Health Organization (WHO) said Wednesday it will send more than one million polio vaccines to war-torn Gaza after the virus was detected in the Palestinian territory’s wastewater.

WHO chief Tedros Adhanom Ghebreyesus said in a press conference that health workers need free movement within Gaza to administer the vaccines in the coming weeks, saying that a ceasefire, or at least a few “days of tranquillity,” was essential to protect Gaza’s children with routine vaccinations.

“The detection of polio in wastewater in Gaza is a tell-tale sign that the virus has been circulating in the community, putting unvaccinated children at risk.”

No clinical cases have yet been detected.

Andrea King, from the WHO’s global health cluster team, said the vaccination campaign would be a “huge logistical challenge.”

“It’s vaccines as well as the associated cold chain supplies that are needed to enter Gaza... as well as the micro-planning within Gaza,” she told the press conference.

“The hope is that if everything lines up, these will arrive in time for the planned vaccination dates later this month, the first round to start on 17 August.”