The Advisory Committee on Immunization Practices (ACIP) has revised its recommendations for the use of the typhoid vaccine to include updated information on the 2 currently available vaccines, the epidemiology of enteric fever in the United States, and the importance of vaccination and other preventive methods for typhoid fever. The typhoid vaccine, coupled with avoiding certain foods and beverages, is becoming increasingly important for foreign travelers in the prevention of typhoid fever.
The 2 typhoid vaccines currently available for use in the United States include a Vi capsular polysaccharide vaccine for parenteral use (Typhim Vi), and an oral, live-attenuated vaccine (Vivotif). They have moderate efficacy in populations where typhoid is widespread. One study showed that the estimated 2.5- to 3.0-year cumulative efficacy was 55% (95% confidence interval [CI], 30%-70%) for the parenteral vaccine, and 48% (CI, 34%-58%) for the oral vaccine. However, studies conflict regarding the effectiveness of this vaccine in young children. One trial found effectiveness of 80% (CI, 53%-91%) in children aged 2 to 4 years, whereas another trial showed no protection in patients from the same age-group. Another study of US travelers estimated 80% protection, but did not address the specific vaccines.
Typhoid (caused by Salmonella enterica serotype Typhi) and paratyphoid (caused by S enterica serotypes Paratyphi A, Paratyphi B, and Paratyphi C) fevers are collectively referred to as enteric fever. Most commonly occurring when water or food has been contaminated by the feces of an infected person, enteric fever can be severe and sometimes life-threatening. The incubation period is 6 to 30 days, and illness onset includes gradually increasing fatigue and fever. Malaise, headache, and anorexia are common symptoms, and a transient macular rash can occur. Serious complications, such as intestinal hemorrhage or perforation, generally occur after 2 to 3 weeks. Untreated patients have been shown to have fatality rates >10%, whereas the overall fatality rate in patients who receive early and correct antibiotic treatment is <1%.
Typhoid fever is uncommon in the United States; however, approximately 90% of cases occur in the United States, in people returning from foreign travel. Most travelers (≥55%) reported that their reason for travel was visiting friends or relatives, and even short-term travel to high-incidence areas is associated with risk for typhoid fever. Although routine typhoid vaccination is not recommended in the United States, the Centers for Disease Control and Prevention recommends that travelers visiting several Asian, African, and Latin American countries receive typhoid vaccination.
The importance of typhoid vaccination in these populations is amplified by the increasing resistance of Salmonella serotype Typhi to antimicrobial medicines (eg, fluoroquinolones) in several areas of the world. Strains of Salmonella serotype Typhi that are multidrug-resistant have become common in many regions, and typhoid fever can be fatal in patients who are treated with drugs to which the organism is resistant. Therefore, pharmacists and clinicians should warn travelers that the typhoid vaccination is not a replacement for careful selection of food and beverages; typhoid vaccines are not 100% effective, and vaccine-induced protection can be weakened by large amounts of Salmonella serotype Typhi.
- Jackson BR, Iqbal S, Mahon B. Updated recommendations for the use of typhoid vaccine—Advisory Committee on Immunization Practices, United States, 2015. MMWR Recomm Rep. 2015;64:305-308.