SAN FRANCISCO - A single injection of microscopic plastic capsules could someday eliminate the need for injections booster vaccination. The new technique, described here yesterday at the annual meeting of the American Chemical Society, could save money for health care by reducing the need for the doctor to repeat visits.
The vaccines against diseases such as polio and tetanus currently are given in several small doses spaced weeks or months apart. But this can pose logistical problems in developing countries and even in some urban areas of the United States, a significant proportion of children fail to return for repeat injections. It was five years ago, a team led by Jeffrey Cleland of the biotech company Genentech in San Francisco set out to simplify the procedure with microspheres, plastic ball a few tens of micrometers through that slowly release drugs as they dissolve into the muscles or other tissues.
to mimic a booster injection, the microspheres have been designed to survive for months in the body, then quickly release the vaccine. The key is found to be using a thicker crust of plastic - polylactidglycolide, the same substance used in medical sutures - to encapsulate small vaccine droplets. Researchers tested the thicker shell microspheres with an experimental vaccine against AIDS, called GP0, developed by Genentech. They injected a group of baboons with a normal dose as a first vaccination, combined with a booster shot nestled in microspheres that dissolve after 40 days. This group had an immune response much higher and more prolonged than those given traditional booster shot injection after 40 days had. Cleland speculates that the microspheres, which took several days to release the vaccine, have done a better job of stimulating the immune system. "The more you can keep antibody levels up, the better you are," he said.
The experts are happy to see the progress. "I am very positive, very happy" with the work says chemical engineer Bob Langer of the Massachusetts Institute of Technology. "Ideally, you can use this method with any vaccine." Haro Hartounian, specialist drug delivery technologies to DepoTech in San Diego, provides that the microspheres will prove more effective than traditional booster shots and - by eliminating this second visit to the doctor - could reduce the cost. Cleland says the technology is ready to be allowed to vaccinemakers willing to give it a shot.
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