Two cancer patients have been taken off their HIV medication after bone marrow transplants seemed to clear the virus from their bodies, but campaigners say it is “by no means a workable cure.”

The Harvard University researchers at Brigham and Women’s Hospital in Boston stressed that it is far too soon to talk about a functional cure as the virus could return at any point.

The two men, who have not been identified, had lived with HIV for about 30 years.

They both developed lymphoma, a cancer, which required a bone-marrow transplant.

It is difficult to get rid of HIV because it hides inside human DNA, forming untouchable reservoirs in the body.

After the transplant, there was no detectable HIV in the blood for two years in one patient and four in the other.

The pair came off their anti-retroviral drugs earlier this year.

Dr Michael Brady, medical director at Terrence Higgins Trust, the UK’s largest HIV and sexual health charity, said: “It is too early to know whether HIV has been eradicated from these men’s bodies or whether it might return. However, the case suggests that what happened to Timothy Ray Brown, the Berlin Patient was perhaps not a one-off.”

Mr Brown has been free of HIV for the past six years following a series of bone marrow transplants in 2007.

Dr Michael Brady added: “A bone marrow transplant is a complex and expensive procedure, which comes with significant risks. For most people with HIV, it would be more dangerous to undergo a transplant than to continue managing the virus with daily medication. While this is by no means a workable cure, it does give researchers another sign-post in the direction of one. Until a cure is found, we urge people to continue using condoms and testing for HIV if they’ve put themselves at risk.”

Gay, bisexual, and other men who have sex with men (MSM) continue to be disproportionately affected by the spread of HIV in the UK; accounting for almost half of all new cases in 2011.