The onset of colder weather has slowed the number of refugees and migrants landing on Greek islands near Turkey but the looming of winter has activists worried more than 15,000 people being held in detention centers and camps will face worsening conditions.

Arrivals on islands from Nov. 19-25 was 751, official figures showed, according to Kathimerini, while 863 people were transferred to facilities on the mainland to ease pressure on overcrowded reception and identification centers human rights groups said aren’t fit for humans.

At the Moria camp on the island of Lesbos, built for a maximum of 3,000 people, more than 5,800 are being held in such appalling conditions that the BBC called the facility the “worst in the world” housing refugees and migrants, most seeking asylum after the European Union closed its borders to them and reneged on promises to Greece to help take some of the overload.

A spillover camp in an adjacent olive grove houses another 1,400 people staying in summer tents, as are hundreds inside the perimeter fences, as the container homes available are all occupied, the paper said.

The official registration and processing center on Samos, built to house 650 people, is currently home to 3,895, with hundreds also being forced to live in summer tents inside and outside the facility.

NGO Doctors Without Borders said it had vaccinated 2,000 children on Lesvos and another 300 on Chios, and is planning to give booster shots to more than 1,000 minors on Samos in the coming days.

In November, Budget cuts imposed by the ruling Radical Left SYRIZA-led coalition have rendered Greece’s asylum system unable to keep up with a torrent of applications to stay in the country which will leave thousands stuck in detention centers and camps, many housed in tents during the winter.

A United Nations envoy warned the refugees and migrants, some 15,000 on islands and more than another 52,000 on the mainland, are in a perilous position after more than 20 human rights groups and activists said conditions in some centers and camps are unfit for humans.

This will be the fourth winter that Greece has said it would improve conditions without fulfilling that pledge despite repeated assurances from the Leftists to help refugees and migrants that Prime Minister Alexis Tsipras said European Union officials were crying “crocodile tears” over.

Philippe Leclerc, the UN refugee agency’s representative in Athens, said EU policy on Greece during the debt crisis was “totally legitimate,” despite Greece’s complaints it hasn’t received enough aid and after a Greek newspaper said Defense Minister Panos Kammenos was shuffling European Union subsidies for the camps and centers to business friends.

LeClerc told The Guardian, which reported on the problem, that Greece “is a state that is affected by the consequences of the financial crisis and public control spending measures … (so) you have an emergency situation on the islands and the mainland, where the state is not fully equipped to respond,” without explaining then why the EU doesn’t.