U.S. Naval Medical Research Center Developing Promising Vaccine for Travelers’ Diarrhea

Capt. Stephen Savarino, Naval Medical Research Center, Head, Enteric Diseases Department

Cmdr. Mark Riddle (left), clinical trial principal investigator, and Capt. Stephen Savarino, physician-scientist who has spearheaded the development of the ETEC adhesin vaccine, shown in the hallway outside the Clinical Trials Center at the Walter Reed Army Institute of Research.

Diarrhea is the most often reported illness among troops in Iraq and Afghanistan, nearly two-thirds of whom reported at least one episode during deployment, half of those requiring medical care.

The number one cause is enterotoxigenic Escherichia coli, or ETEC which is found most often in food and sometimes in water. This type of illness is commonly called Travelers’ Diarrhea. To infect a person, ETEC bacteria must latch onto the intestinal lining. ETEC are covered with fine hairs and at the tip of each hair is a sticky protein that makes it possible for ETEC to attach onto the intestinal lining. Once it is attached, it rapidly multiples and releases a toxin that triggers diarrhea. The signs and symptoms include cramps, nausea, watery diarrhea and sometimes fever.

There is no vaccine available today to prevent travelers’ diarrhea. But we hope to change that. Our team at the Naval Medical Research Center in Silver Spring, Md. has developed a vaccine that alerts the body to produce anti-attachment and anti-toxin antibodies to defend against infection. We are heading into the first clinical trial with a favorable tailwind in that all of the data that we’ve accrued in preparation for this clinical trial has been very promising. 

Researchers will administer the test vaccine by skin patch, and then collect specimens to gauge the body’s ability to mount an immune defense against ETEC. The primary outcome for this first trial is safety. We hope the vaccine will be safely tolerated and not result in any adverse events.

Electron micrograph of the ETEC bacterium, with the hair-like fimbriae radiating from its surface. The adhesin-based vaccine has been engineered from the sticky protein found at the far tips of each of these hairs.

An additional outcome is immunogenicity. We hope this trial will demonstrate that the vaccine results in robust immune responses and specifically immune responses in the G.I. tract.