After decades of slow progress, therapeutic vaccines that direct the immune system to attack tumours could soon become a fixture of cancer treatment.

Vaccines are usually used to prevent infectious diseases. A therapeutic cancer vaccine is different. Rather than teaching the immune system to recognize pathogens in advance of an infection, these vaccines use identifying proteins produced by cancer cells, known as antigens, to provoke a powerful immune response to existing tumours.

Numerous therapeutic cancer vaccines, on the basis of a variety of approaches, are showing encouraging results in trials.