The reports from Dhaka are hopeful. It is 2005, and Dr. Firdausi Qadri and colleagues at the International Center for Diarrheal Disease Research, Bangladesh, are testing a new cholera vaccine on children. In their study, a single dose of live, crippled bacteria goes down easily in a fizzy drink. Within days, most of the children are showing exactly the kind of robust immune response that should enable them to fend off an attack from the deadly pathogen, with no notable side effects.

The study follows a similar success immunizing adults in the same city. The stage is now set for a large-scale trial to test the vaccine, known as Peru-15, to prevent the seasonal flare-ups of life-threatening diarrhea that dog the poor in Bangladesh and other regions of the developing world.

In the developed world, too, Peru-15 is close to final testing as a rapidly acting traveler’s vaccine.