Typhoid Vaccine Guidelines
Typhoid vaccination is strongly recommended for travelers to endemic areas (particularly South Asia, Latin America, Asia, and Africa), household contacts of documented typhoid carriers, and laboratory workers with S. typhi exposure, using either the oral Ty21a vaccine or injectable Vi polysaccharide vaccine, both offering 50-80% protection. 1, 2
Who Should Receive Typhoid Vaccination
Primary Indications
- Travelers to endemic regions with recognized risk of S. typhi exposure, particularly those visiting developing countries in Latin America, Asia, and Africa with prolonged exposure to potentially contaminated food and water 1, 2
- Household contacts with intimate exposure to documented typhoid fever carriers 1, 2
- Laboratory workers (microbiologists and personnel) who frequently work with S. typhi cultures 1, 2
Geographic Risk Assessment
The highest risk destinations include Pakistan (24 per 100,000 travelers), Cambodia (20 per 100,000), Nepal (14 per 100,000), India (12 per 100,000), and Sri Lanka (9 per 100,000), with the Indian subcontinent representing the greatest travel-associated risk 3. Real-world effectiveness data from US travelers demonstrates 80% vaccine effectiveness (95% CI: 66-89%) 4.
Available Vaccine Options
Oral Live-Attenuated Ty21a Vaccine (Vivotif)
- Efficacy: Reduces laboratory-confirmed infection by approximately 67% for at least 4 years, with three-year cumulative efficacy of 50% 2
- Safety profile: Adverse event rates comparable to placebo (<1/100,000 doses), with fewer adverse reactions than parenteral vaccine 2
- Licensed for: Immunocompetent individuals ≥6 years of age 1
Injectable Vi Polysaccharide Vaccine
- Efficacy: 51-76% effective in preventing typhoid fever, with three-year cumulative efficacy of approximately 55% 2
- Safety profile: Causes injection site reactions but rarely systemic effects 2
- Licensed for: Children ≥2 years of age and adults 1
Vi-TT Conjugate Vaccine
- Superior efficacy: Four-year efficacy of 78%, recommended by WHO due to superior efficacy profile 2
Administration Protocols
Oral Ty21a Vaccine (Adults and Children ≥6 Years)
- Dosing regimen: One enteric-coated capsule taken on alternate days for a total of four capsules 1, 2
- Administration technique: Take with cool liquid no warmer than 37°C, approximately 1 hour before meals 2
- Booster schedule: Revaccination with entire four-dose series every 5 years under continued exposure 1, 2
Injectable Vi Polysaccharide Vaccine
- Adults and children ≥10 years: 0.5 mL subcutaneously or intramuscularly as a single dose 2
- Children 6 months to <10 years: 0.25 mL subcutaneously on two occasions separated by ≥4 weeks 2
- Booster schedule: Every 2-3 years under conditions of continued or repeated exposure 1, 2
Critical Limitations and Precautions
Vaccine Limitations
- Vaccination is NOT a substitute for careful food and beverage selection, as vaccines are not 100% effective and protection can be overwhelmed by large inocula of S. typhi 1, 2
- No protection against Salmonella Paratyphi A, B, or C infection with current typhoid vaccines 1
Contraindications
- Inactivated vaccine: Contraindicated in individuals with history of severe local or systemic reaction after previous dose 2
- Oral vaccine: Not recommended for children <6 years of age or immunocompromised persons, including those with asymptomatic HIV infection 2
Common Pitfall
The most significant clinical error is over-relying on vaccination alone without emphasizing food and water precautions, particularly given that only 5% of typhoid cases in US travelers had received vaccination compared to 20% of paratyphoid cases (against which the vaccine offers no protection) 4. This underscores both the importance of vaccination AND behavioral risk reduction.