Smallpox jabs 'can curb HIV virus'

The claim follows laboratory studies showing the vaccine's powerful ability to curb the Aids virus.

It may have offered protection to people in the early days of the HIV epidemic, the findings suggest. But this would have been removed once smallpox was eradicated and the vaccine withdrawn.

Smallpox immunisation was gradually phased out between the 1950s and 1970s. Since that time, rates of HIV infection have increased exponentially around the world.

Scientists in the US studied white blood cells taken from people recently immunised with the smallpox vaccine, vaccinia.

They found that immunisation led to a five-fold reduction in the ability of HIV to replicate in the cells.

Dr Raymond Weinstein, from George Mason University in Mannasas, Virginia, said: "There have been several proposed explanations for the rapid spread of HIV in Africa, including wars, the reuse of unsterilised needles and the contamination of early batches of polio vaccine. However, all of these have been either disproved or do not sufficiently explain the behaviour of the HIV pandemic.

"Our finding that prior immunisation with vaccinia virus may provide an individual with some degree of protection to subsequent HIV infection suggests that the withdrawal of such vaccination may be a partial explanation."

The research is published today in the journal BMC Immunology.

Dr Weinstein believes smallpox vaccination may produce long-term changes in the immune system that have an impact on HIV. Both types of virus exploit the same "receptor" molecule on the surface of white blood cells.

Dr Weinstein said the evidence was not yet strong enough to justify bringing back the smallpox vaccine.

"While these results are very interesting and hopefully may lead to a new weapon against the HIV pandemic, they are very preliminary and it is far too soon to recommend the general use of vaccinia immunisation for fighting HIV," he said.