Acute gastroenteritis is associated with sudden onset of disturbances in gastrointestinal function such as nausea, vomiting, diarrhea (sometimes bloody), abdominal cramps, and fever. The illness typically lasts less than 2 weeks and is most commonly associated with an infectious etiology. Treatment with antibiotics and anti-motility agents may be indicated depending upon the causative infectious agent and the severity of symptoms. Acute gastroenteritis is very common and is estimated to cause 179 million cases, over 470,000 hospitalizations, and over 5,000 deaths among U.S. residents each year.¹ People usually acquire the infectious agents (bacteria, viruses, or protozoa) via the ingestion of contaminated food or water or direct person-to-person contact. Although developed nations have reduced the risks of exposure to gastrointestinal pathogens by building infrastructures of sanitary systems for water distribution and sewage disposal, transmission via contaminated food and water remains common.

In military populations, the threat of gastroenteritis is enhanced when personnel are serving in field settings as part of training, deployment, or in theaters of combat. The efforts of military preventive medicine and environmental health assets focus on minimizing the risks of food-borne and waterborne disease not only in the peacetime settings of congregate housing and field training but also in the austere settings of combat. Although such preventive measures are effective, they do not prevent all gastrointestinal illness.

Immunizations provide a powerful class of defense against infectious diseases. Although vaccines protecting against at least 30 different infectious diseases have been approved by the U.S. Food and Drug Administration (FDA) on the basis of evidence of safety and effectiveness, only 2 of those vaccines (cholera, rotavirus) offer the prospect of an immunological defense against a specific cause of gastroenteritis.²

The FDA-approved cholera vaccine is a live, orally administered vaccine that offers protection against the Vibrio cholerae O1 strain, a bacterium capable of causing gastroenteritis at the more severe end of the spectrum (i.e., cholera).³ Cholera vaccine is not a routinely administered vaccine, and no country or territory currently requires vaccination against cholera as a condition of entry for visitors. The Advisory Committee for Immunization Practices and the Centers for Disease Control and Prevention recommend cholera vaccine for individuals 18–64 years of age who reside in an area with endemic cholera or who will travel to an area that is experiencing a cholera outbreak or that has a high risk of cholera because of a humanitarian crisis.3 There are also 3 other oral vaccines for cholera that are not approved for use in the U.S. These vaccines are killed vaccines and they require 2 doses at least a week apart for full protection.³

Rotavirus-caused gastroenteritis affects nearly all children by the time they reach the age of 5 in both developed and underdeveloped regions around the world.⁴ The live, oral vaccine must be given in 2 or 3 doses, depending upon the brand of vaccine used. The first dose should be administered before 14 weeks and 6 days of age and the last dose by 8 months and 0 days of age. The vaccine is not indicated for adults.⁵

The better-recognized bacterial species associated with gastroenteritis are members of the genera Escherichia, Salmonella, Shigella, Campylobacter, Clostridium, Staphylococcus, Bacillus, Yersinia, and Vibrio. Except for V. cholerae, there are no vaccines for any of these bacteria. Protozoan causes of gastroenteritis are less commonly identified than the bacterial and viral causes, but there are no vaccines for the more common protozoans (i.e., Giardia, Cryptosporidium, and Cyclospora). There are numerous viral causes of gastroenteritis, but the best known are the caliciviruses (including noroviruses), astroviruses, and rotaviruses. Except for the rotavirus vaccine, there are no FDA-approved vaccines to protect against the viral causes of acute gastroenteritis. It has been estimated that noroviruses are the cause of about one-third of all cases of gastroenteritis in the U.S., so an efficacious norovirus vaccine has been the subject of much research to date.⁶ The quest for a norovirus vaccine or vaccines has proven especially challenging because of the relatively short period of immunity following a clinically significant infection, the heterogeneity of strains of norovirus, and the inability to culture the virus in the laboratory.⁶ Despite these challenges, several norovirus vaccine candidates are currently being evaluated in human clinical trials, including a study of a bivalent vaccine in military recruits.⁷

The incidence rates of most types of acute infectious gastroenteritis are not susceptible to reduction by vaccines. The prevention of gastroenteritis (and other diseases) spread through fecal contamination of water, food, or fomites depends upon diligent implementation of the wide spectrum of measures that constitute sanitation, hygiene, environmental health, food safety, and disease surveillance. Responsibilities in these areas fall to government agencies, suppliers of food and water, educators, public health authorities, healthcare providers, parents, and individuals.

A current review of required immunizations for Department of Defense personnel by Combatant Command is available at https://health.mil/Military-Health-Topics/Health-Readiness/Immunization-Healthcare/Vaccine-Recommendations/Vaccine-Recommendations-by-AOR.

Author affiliations: GDIT contracted to the Armed Forces Health Surveillance Branch, Defense Health Agency, Silver Spring, MD (Dr. O'Donnell); Immunization Healthcare Branch, Public Health Division, Defense Health Agency, Falls Church, VA (Col Rans).

References

1. Scallan E, Griffin PM, Angulo FJ, Tauxe RV, Hoekstra RM. Foodborne illness acquired in the United States—unspecified agents. Emerg Infect Dis. 2011;17(1):16–22.
2. U.S. Food and Drug Administration. Vaccines licensed for use in the United States. https://www.fda.gov/vaccines-blood-biologics/vaccines/vaccines-licensed-use-united-states. Accessed 21 Feb. 2020.
3. Centers for Disease Control and Prevention. Cholera–Vibrio cholerae infection. Vaccines. https://www.cdc.gov/cholera/vaccines.html. Accessed 21 Feb. 2020.
4. Dormitzer PR. Rotaviruses. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:1854–1864.
5. Centers for Disease Control and Prevention. Rotavirus vaccination: information for health care professionals. https://www.cdc.gov/vaccines/vpd/rotavirus/hcp/index.html. Accessed 3 Jan. 2020.
6. O’Ryan M, Vidal R, del Canto F, Salazar JC, Montero D. Vaccines for viral and bacterial pathogens causing acute gastroenteritis: Part I: Overview, vaccines for enteric viruses and Vibrio cholerae. Hum Vaccin Immunother. 2015;11(3):584–600.
7. Mattison CP, Cardemil CV, Hall AJ. Progress on norovirus vaccine research: public health considerations and future directions. Expert Rev Vaccines. 2018;17(9):773–784.