Pembrolizumab helps the body's defence system attack cancer, while the vaccine gives it specific information about which cells to target.

A new cancer vaccine has reduced the risk of melanoma returning or patients dying by 42 per cent when combined with an existing cancer drug, raising hopes of preventing the disease from coming back after surgery.

Melanoma is a type of skin cancer that can spread to other parts of the body. In some patients, the cancer returns even after surgery has removed the tumour, making further treatment important.

The international study involved 1,137 patients at 157 sites worldwide whose melanoma had been removed through surgery but who remained at risk of the cancer returning.