US army scientists have discovered that the toxin produced by the cholera bacterium stimulates an immune response even when it is put on the skin, and that it speeds up immune responses to any other foreign protein added to it.
Tests on laboratory mice have confirmed cholera's effectiveness in helping the body to generate antibodies to diphtheria and tetanus.
Trials on humans are due to start at the end of next month. If all goes well the needle-free system could be available commercially within the next five to 10 years.
"We can take an off-the- shelf vaccine, mix it with cholera toxin and get a very nice immune response from that off-the-shelf type vaccine," said Dr Gregory Glenn, of the department of biochemistry at the Walter Reed Army Institute of Research, in Washington DC.
"The implications are that one could eliminate needles."
The army scientists' work is reported today in the science journal Nature.
The method could revolutionise vaccination programmes in developing countries, where the cost of needles for injections can be prohibitive.
The idea of using a potentially dangerous disease to produce medical benefits - the basis of immunisation - is also being suggested for techniques such as gene therapy.
Some scientists have suggested using a weakened form of HIV, the virus that causes Aids, to carry out gene therapy for genetic diseases such as cystic fibrosis.
Because HIV adds its own genetic material to the host, it could act as the carrier for helpful genes - such as those to cure cystic fibrosis. However, that work is still in its early stages.
Cholera is a more promising candidate for pain-free immunisation. Though widely feared as a disease, its real danger lies in its dehydrating effects.
When consumed (usually through infected water), the bacteria produce a toxin which inflames the gut and leads to diarrhoea and vomiting. The rapid fluid loss can seriously weaken the body. But if the lost fluids are replaced from uncontaminated sources, the immune system can usually overcome the infection.
In that sense, the cholera toxin is not deadly - instead, the principal risk arises from its side-effects.
Thus it makes an ideal candidate as an "adjuvant" for helping provoke an immune response.Reuse content