A vaccine campaign against the coronavirus kicked off in Syria’s last rebel-held enclave on Saturday, with a 45-year-old frontline nurse becoming the first to receive a U.N.-secured shot.

Nizar Fattouh, a nurse in Ibn Sina Hospital in Idlib city, was administered one of 53,800 AstraZeneca vaccines delivered to northwest Syria through Turkey on April 21.

The vaccines come amid a new surge of COVID-19 cases in the war-torn country. Syria supplies of oxygen are depleted and its hospitals were already overwhelmed from 10 years of conflict and deteriorating healthcare services.

The AstraZeneca vaccines were delivered to the rebel-controlled area through a border crossing with Turkey, the northwestern territory’s only gateway to the outside world.

Idlib health official Yasser Najib said the vaccine doses were provided through the U.N.-led COVAX program for the world’s poor and developing nations.

Najib said the vaccination campaign will last 21 working days, starting Saturday in 2 of the enclave’s largest hospitals. On Monday, the campaign will unfold in other health centers, he added.

The small quantity will prioritize healthcare staff and aid personnel who are on the frontline of the battle against COVID-19, according to the official. Infections among healthcare workers in the enclave have been high, accounting for as many as 30% of confirmed cases at one point.

There are more than 21,000 confirmed cases in the rebel-held enclave, home to 4 million people, most of them displaced from various parts of Syria by the conflict. At least 641 have died in the area from COVID-related complications. Conflict has subsided in the area, but outbreaks of violence are still reported.

Syria has been divided by the war so inoculations in government-controlled areas, around 60% of the country’s territory, are managed and take place separately.