Skin patch vaccine to prevent travelers' diarrhea

There are more than 6 billion people living around the world but it may be still be surprising that travelers' diarrhea affects as many as 22,000 of them every day.

Travelers' diarrhea (TD) is the most common illness affecting travelers. Each year between 20%-50% of international travelers, an estimated 10 million persons, develop diarrhea. Montezuma's revenge is the colloquial term for any cases of traveler's diarrhea contracted by tourists visiting Mexico. The name humorously refers to Montezuma II (1466-1520), the ruler of the Aztec civilization who was defeated by Hernándo Cortés, the Spanish conquistador. It is estimated that 40% of foreign traveler vacations in Mexico are disrupted by infection.


Image source: Escherichia coli, Wikipedia, public domain.

The most common causative agent is enterotoxigenic Escherichia coli (ETEC). The primary source of infection is ingestion of fecally contaminated food or water.

In a phase II study published in The Lancet, 178 healthy adults (aged 18–64 years) who planned to travel to Mexico or Guatemala were vaccinated before travel, with two skin patches given 2–3 weeks apart. Patches contained either 37·5 μg of heat-labile toxins from E coli (LT) or placebo.

According to the study authors, the vaccine was safe and immunogenic. The 59 LT-patch recipients were protected against moderate-to-severe diarrhea (protective efficacy 75%) and severe diarrhea (protective efficacy 84%). LT-patch recipients who became ill had shorter episodes of diarrhea (0·5 days vs 2·1 days) with fewer loose stools (3·7 vs 10·5) than placebo.

The authors concluded that ETEC diarrhea illness occurring in 10% of cases of TD. The vaccine patch is safe and feasible, with benefits to the rate and severity of travelers' diarrhea.

References:
Use of a patch containing heat-labile toxin from Escherichia coli against travellers' diarrhoea: a phase II, randomised, double-blind, placebo-controlled field trial. The Lancet 2008; 371:2019-2025.
Travelers' Diarrhea. CDC.
Traveler's diarrhea, from Wikipedia, the free encyclopedia.
Top image source: Flickr, Creative Commons license.

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