Most vaccines work by teaching the immune system to recognize harmful viruses or bacteria before a person gets infected and becomes unwell. A few cancer vaccines do this, too. For example, a vaccine is given to young people as protection against human papillomaviruses that can cause cervical cancer.

But scientists are also developing cancer vaccines that could be used as treatments, after cancer has been found.

These vaccines work by teaching the body’s immune system to distinguish between healthy cells and abnormal cancer cells. To do this, researchers need to identify proteins that are made by cancer cells but not by healthy cells. These proteins can be used like a barcode. The vaccine teaches the body’s immune cells to ‘read’ the barcode, as a way of identifying the cancer. This video explains how these vaccines are made, and the pros and cons of various types of cancer vaccine.