Police and paramedics were called to the scene between Wootton and Whippingham at just before 07:40 following what is thought to be a collision between a vehicle and a push bike.
Traffic is heavy in and around the area and therefore motorists are advised to find an alternative route.
Southern Vectis buses are diverting via Staplers until further notice.
UPDATE @ 08:35 – A cordon has been erected at the bottom of Lushington Hill – near where the speed limit changes to 50mph – as Police continue their investigations.
The road has been placed under a hard road closure in both directions and is likely to remain closed for some time.
The casualty is said to have sustained a head injury and has been rushed to St Mary’s Hospital, Newport.
UPDATE @ 10:57 – Lushington Hill has now re-opened in both directions.
The casualty is said to be in a stable condition.