Travelers to Mexico and many other locations around the world are warned to beware of Montezuma’s revenge and don’t drink the water.  Doctors refer to Montezuma’s revenge as travelers’ diarrhea and it does come from drinking the water and eating exotic foods during travel.

Until lately, there has been no way to prevent travelers’ diarrhea and the best medical advise has been to avoid contracting it whenever possible.  A newly developed vaccine is being tested, however, that is proving highly effective in preventing the common symptoms blamed for putting a damper on many a vacation.

Travelers’ diarrhea is most often caused by infection from the enterotoxigenic E. coli (ETEC) bacteria.  The vaccine against it, developed by the Iomai Corporation, has proven to be significantly successful in preventing or minimizing the symptoms of illness in Phase 2 trials conducted recently on travelers to Mexico and Guatemala.

All 170 of the study participants was healthy, between the ages of 18 and 64, and agreed to the patch-type vaccine or a placebo.  They also received medical evaluation in the country of their destination.

Only three of the 59 study participants treated with the Iomai vaccine patch experienced diarrhea described as moderate or severe, while 24 of the 111 travelers receiving placebo treatment reported moderate or severe diarrhea.  Suffering was documented as severe in only one traveler in the vaccine group but in 12 of the placebo group.

Vaccination against travelers’ diarrhea involved two doses, with the second dose following the first one after an interval of two to three weeks.  The second dose was administered a week before each study volunteer traveled.  Of the vaccinated travelers who did become ill, diarrhea lasted an average of only half a day while the placebo group reported an average of two days of sickness.

Of the 55 million people expected to travel internationally this year, almost 20 million of them will experience travelers’ diarrhea.  The illness can wreak havoc on the best-made vacation plans but can also trigger the onset of irritable bowel syndrome, which can be quite painful and have life-long effects.

In addition to preventing Montezuma’s revenge, the needle-free Iomai vaccine patch may prove beneficial in treating diarrheal diseases in children in the developing world.  Diarrhea associated with the same strain of E. coli strikes 210 million children around the world each year, killing almost 380,000 of them.

Before becoming the first vaccine against travelers’ diarrhea approved for use in the United States, the vaccine must undergo a Phase 3 trial, expected in 2009.

The research team, affiliated with the University of Texas School of Public Health and the Iomai Corporation, have recently published the findings of their Phase 2 study in the distinguished medical journal, Lancet.