Health authorities have confirmed 18 cases of coronavirus linked to a special needs school in Sydney’s north, with students, their families and staff all in isolation.

NSW Health has confirmed the cases associated with the Giant Steps special education school in Gladesville on Sydney’s Lower North Shore, including three staff, seven students and eight family members.

The school caters for students with severe autism.

A NSW Health spokesperson said the first cases were notified on August 5, the school had been closed and families and staff were isolating.

“NSW Health takes proactive steps to contact all close contacts of the case, to give advice on testing, isolation, symptoms to be aware of, and their level of risk,” the spokesperson said in a statement.

Elsewhere in regional NSW, the lockdown of the Hunter and New England region has been extended by another week after 24 new cases arose overnight.

Also following a lockdown imposed in the ACT, NSW Health has advised that anyone in NSW who has been in the territory since August 5 must isolate and only leave home for essential reasons.

NSW recorded 345 new local cases across the state in the 24 hours to 8pm on Wednesday, with at least 91 in the community while infectious.

The reporting period also saw two deaths from the disease, both Sydney men in their 90s.

The state looks set to break through the 50 per cent mark for vaccine coverage this week.

Some 49.02 per cent of NSW residents aged 16 and over have had one dose of the vaccine, and 25.06 per cent are fully vaccinated.

-AAP