The news coming out of the laboratory was scary. Not only had a promising new HIV vaccine failed, it may have increased the incidence of the disease in previously healthy volunteers. Scientists are now working hard to discover the cause of the biggest setback to HIV vaccine research for years.

The mystery, which has attracted almost no attention but could have huge implications for all vaccine research, centres on the V520 vaccine developed by Merck. The vaccine comprised a common cold virus with three HIV genes stitched into it (the cold virus is used simply to smuggle the HIV genes into the body). The plan, as with any vaccine, was that these harmless HIV genes would goad the immune system into making antibodies capable of fighting off a genuine infection.

Fifteen hundred high-risk, healthy individuals - many were sex workers - received the vaccine in 2005. Two years later the vaccinated group were just as likely to have caught HIV as the group who received a placebo, showing the vaccine didn't work.

But closer inspection revealed something seriously amiss among participants who, when recruited, had high levels of antibodies to the cold virus. When these cold-sensitive people were vaccinated their risk of getting HIV doubled compared with cold-sensitive people who received a placebo.

The vaccine itself will not have infected participants but scientists are desperate to find out why it apparently made recipients more vulnerable to infection. “We are analysing the data to try to determine if the results are due to immune responses induced by the vaccine, differences in study populations, or some other biological phenomenon,” said Dr Keith Gottesdiener, of Merck Research Laboratories.

The findings will be crucial, given that cold viruses are regularly used in experimental vaccines. One Merck researcher said that “the whole field will come apart at the seams” without an intensive investigation.

Leafing through my Penguin Book of Historic Speeches I happened upon an oration given by the suffragette Emmeline Pankhurst. During her era, a child born in wedlock had only one legal parent - the father. She said: “[If women had the vote] .. . the law would have said that as Nature has given to children two parents, so the law should recognise that they have two parents.” We can safely assume she meant one of each gender.

How odd, then, it seems for me to be attending a conference in Westminster tonight on the “need for a father”. The issue of paternity is being examined for its relevance to the welfare of a child born to two lesbians.

Neither nature nor science can yet create a human life from just two biological mothers or two biological fathers. For the State, therefore, to excise men from the business of parenting seems dishonest as well as discriminatory.

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