Traveler’s Diarrhea Vaccine Shows Promise

Each year between 20%-50% of international travelers—about 10 million people— develop diarrhea. The onset of “Traveler’s Diarrhea” (TD) usually occurs within the first week of travel but may occur at any time while traveling, and even after returning home. In a recent study by researchers at The University of Texas School of Public Health, a new patch-based travelers’ diarrhea vaccine has been found to provide significant relief from diarrhea. The study results were published in a recent edition of the Lancet.

In the study, 170 travelers to Mexico and Guatemala were monitored. Of 59 individuals receiving the vaccine, only 3 suffered from severe or moderate diarrhea, while close to 24 people who took the placebo suffered from moderate or severe diarrhea.

“These results suggest that the Iomai patch has the potential to fundamentally change the way we approach prevention of this disease, an ailment against which we now have very few weapons,” said Herbert L. DuPont, M.D., professor and director of the Center for Infectious Diseases at The University of Texas School of Public Health and the principal investigator of the trial. “If these results are replicated, the Iomai vaccine will have the potential to not only mitigate a disease that sickens millions each year but also keep some patients from going on to develop the chronic symptoms of irritable bowel syndrome.”

The Trek Study was done in collaboration with UT Houston, the Johns Hopkins Bloomberg School of Public Health and other institutions. Two doses of the vaccine patch or a placebo were given to each volunteer, 2 to 3 weeks apart. The last dose was given a week before travel.

Detailed diaries were kept by travelers, with in-country checkups. The study was designed to evaluate the safety of the vaccine and the incidence of enterotoxigenic E. coli (ETEC) bacteria—the most common cause of travelers’ diarrhea. No vaccine-related serious side effects were reported. Of the few vaccinated patients who became sick, the diarrhea lasted only half a day on average, while those in the placebo group endured two days of illness and more than twice as many loose stools. Although not statistically significant, the frequency of new-onset irritable bowel syndrome, a long-term consequence of travelers’ diarrhea, was three times greater in placebo than vaccine recipients.

Approximately 55 million travelers are expected to visit countries where bacteria causing diarrhea are endemic, notably Africa, Asia and Latin America, and of these it is anticipated that 20 million will contract diarrhea. Apart from abdominal cramps and dehydration, travelers are also at higher risk of developing irritable bowel syndrome. Children are at special risk in the developing world, where diarrhea linked to enterotoxigenic E sickens 210 million children, killing an estimated 380,000 of them each year.

“Bacterial diarrheal disease is a significant medical problem both for children and travelers, and our technology represents both an advance in vaccine delivery and a breakthrough in the field of infectious disease,” said Gregory Glenn, M.D., Iomai’s chief scientific officer. “We look forward to targeting both the significant travelers’ market and developing the vaccine for the children in the developing world who still suffer serious morbidity and mortality from this disease.”

Researchers at The University of Texas School of Public Health studied the patch-based vacine as part of the Phase 2 study in conjunctoin with the Iomai Corporation. Iomai plans to initiate a Phase 3 program for the needle-free vaccine patch vaccine in 2009. If approved, the Iomai vaccine would be the first vaccine for travelers’ diarrhea available in the United States.

Source: Lancet, June 2008

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