The CEO of Children's Health Ireland has said it "will be weeks" before the IT systems in Temple Street, Crumlin, Tallaght and Children's Health Ireland at Connolly hospital are operating normally following the cyber attack nearly five weeks ago.

Speaking on RTÉ's News at One, Eilísh Hardiman said this is because their systems are not linked up and "that integration is slow and painful".

She said at the moment, when they put something in place, something else goes down and access to care is their greatest operational challenge at the moment.

Ms Hardiman said at the moment, they are not able to get through those patients on waiting lists because they are trying to reduce the burden on their labs.

Their lab systems are not connected at the moment, she explained, and while they are up and running individually as IT systems, they are not connected so paper still has to be passed around the system.

Ms Hardiman added that they will start to open up services "according to how our labs can function".

The staff in these hospitals are depending on paper and it was only last week that they got some of their core systems back up and running, she added.

They have 2,500 IT systems and they only have ten core ones back up, the CEO commented.

80% of its 2,500 pieces of hardware such as laptops and servers have been replaced or restored, Ms Hardiman said.

In relation to Temple Street, Crumlin and Connolly, Ms Hardiman said parents are being contacted to attend scheduled outpatient services.

She said the emergency departments in these hospitals are open, but they are slower because there are still some paper processes ongoing.

Tallaght children's services are fully functioning and are operating as normal.