A British doctor's ingenuity may revolutionise innoculation against tuberculosis in developing countries, preventing many thousands of deaths.

Dr John Lunn, a retired consultant in community health from Buckinghamshire, has devised a simple, cheap, disposable injector which will allow the benefits of the BCG vaccine to be enjoyed by millions more children worldwide.

A spokesman for UN childrens' organisation UNICEF, which runs immunisation programmes in developing countries, described the invention as 'exciting'.

In developing countries, old fashioned injectors designed for teenagers or adults are being used by ill-trained staff, and most often to vaccinate babies against TB.

So the BCG vaccine, which needs to be precisely delivered in exactly the right quantities, is often wasted - leaving the child with no protection against one of the third world's major killers.

Learning of the problems faced by South Africa, which has found no decrease in the rate of tuberculous meningitis despite widespread vaccination efforts, Dr Lunn teamed up with an engineering firm there to develop a solution.

Less than 30 pence a time

The new injector (right) costs 30p - the other �20 plus �1 a shot

The result is an injection device which delivers the right dose to the right spot every time - and costs less than 30 pence.

Previous disposable injectors - essential in countries where AIDS and hepatitis B are rife - initially require the purchase of at least one �20 syringe handle, and disposible needles are �1 each, making them prohibitively expensive for third world countries.

Dr Lunn sees the potential for his brainchild: "It fits all the requirements of healthcare in developing countries.

"It doesn't need skilled personnel to work it and it injects to precisely the right depth every time. There are a great many countries where this could be of use.

"If you are having to pay out a minimum of �20 per clinic, plus �1 per child inoculated, that is way too dear for many health systems."

Sally Burnheim, a spokesman on immunisation for UNICEF UK, said: "This will certainly benefit our work.

"Particularly in Africa, conflicts can make it very difficult to find skilled health workers, so anything that is simple will help.

"If it costs less, that will help as well.

"TB is killing more people than ever before. It is the biggest killer among infectious diseases."

In Southern India, the BCG vaccine currently has practically a zero success rate, although scientists are unsure whether the fault lies in the way it is delivered, or perhaps inbuilt genetic differences which render it useless.

A BCG vaccine, unlike other injections, which are given into muscle or just beneath the skin, has to be given precisely within the skin layer itself.

This means that a few millimetres difference may either make the injection ineffective, or lead to unpleasant complications like huge ulcers.

Birth the only opportunity

In many developing countries, the only time the injection can be given is immediately after the birth of the child. Once the baby leaves the hospital, the authorities have no way of tracing it.

But this creates more difficulties. Dr Lunn said: "The skin of a baby is thinner, and hasn't got the same resistance to pressure. It becomes excessively difficult to give the injection with traditional injectors."

The injector will initially be used to help South African township children

The injector has already been successfully tested against fresh skin from bodies, and the South African company is about to produce the first batch.

With an estimated one million births a year in South Africa alone, the potential market is immense.

The WHO now estimates that around three million people die worldwide from TB every year.

Dr Lunn said: "It's a bigger killer than AIDS, but it doesn't receive as much attention."

Most British schoolchildren are inoculated against TB between the age of 11 and 13, leaving the distinctive "BCG scar" on their upper arms.

If contracted, it can be treated with a combination of antibiotics for a six month period, but resistance to the drugs is increasing, particularly in developing countries.