Scientists at the Imperial College of London are launching trials that could lead to a breakthrough in developing the world’s first HIV vaccine. At present, the best preventative treatment is PrEP, a pill that is taken daily and which offers a high degree of protection against HIV.

About 60 volunteers are being recruited by Imperial’s clinical research facility at Hammersmith hospital. They will receive three vaccination pills over a year.

The pills, manufactured by the US pharmaceutical company PaxVax, do not contain the HIV virus but a small amount of adenovirus 4, which has been engineered to express the HIV protein. So there is no risk of getting HIV.

As part of the trial, participants will swallow this tablet. The virus will replicate to a minor extent in the gut and then die off, but it is hoped that this will give out antibodies in mucosal surfaces in the vagina and rectum, the sites that HIV would normally enter. The level of antibodies will then be measured and tested against HIV, to ascertain whether these antibodies neutralise the virus.