See the detailed stories on these vaccines:
Mucosal Tissues Offer Tempting Targets,
Success of Edible Vaccine May Depend on Picking Right Fruit, and
Transcutaneous Methods Get Under the Skin
All trigger disease resistance in systems other than the blood. And examples of all approaches use cholera toxin to fortify that resistance. Genetically engineered fruits and vegetables use it to gird the gut against pathogens. Some nasal methods employ it to marshal sinus lining strength against infectious diseases. And some transdermal strategies apply it to steel the skin's immune responses against childhood ailments.
Some needle-free vaccines utilize multiple approaches. For example, Aviron Inc.'s nasal flu spray triggers a strong response in the mucosal linings of the respiratory system, but it also causes...