Vaccines without a sticking point.

Getting vaccinated generally means enduring an unpleasant needle jab. Preliminary studies in mice, however, suggest that injectable liquid vaccines can be processed, dried to a powder, and painlessly pushed into the skin with a puff of helium gas from a pneumatic gun.

The skin is an ideal target for vaccines, says Dexiang Chen of PowderJect Vaccines of Madison, Wis. It contains a powerful network of immune cells acting as the body's primary defender against infection (SN: 9/11/99, p. 164).

Powders made from flu, tetanus, hepatitis B, and other vaccines induced immune responses in mice as well as injected vaccines do, Chen reports. Because immune cells lie close to the skin's surface, the powdered vaccine can contain just a tenth the amount of material required in standard formulations and still work--at least in mice, he says.

"This technique is preliminary but promising," says Philippe H. Lagrange of the St. Louis Hospital in Paris. Most liquid vaccines require refrigeration, but the powdered vaccines will probably be stable at room temperature, making them especially useful in developing countries, he adds.

So far, Chen and his colleagues have not worked with any vaccines that contain live, weakened viruses. Drying these formulations will be more complicated, but possible, Chen says.