What are the available typhoid vaccines, their dosing schedules, age indications, booster recommendations, and contraindications?

Typhoid Vaccines: Available Options and Recommendations

Two main typhoid vaccines are available: oral live-attenuated Ty21a vaccine and parenteral Vi polysaccharide vaccine, with newer typhoid conjugate vaccines (TCVs) now representing the preferred option for all ages according to WHO recommendations.

Available Vaccine Types

1. Oral Live-Attenuated Ty21a Vaccine

• Dosing schedule: 4 enteric-coated capsules taken on alternate days (days 1,3,5,7) 1
• Administration: Take with cool liquid no warmer than 37°C, approximately 1 hour before meals; must be refrigerated 1
• Age indication: Adults and children ≥10 years (can be used in children <10 years) 1
• Efficacy: Prevents approximately 50% of typhoid cases over 2.5-3 years (moderate-certainty evidence) 2
• Booster: Complete 4-dose series every 5 years under continued exposure 1

2. Parenteral Vi Polysaccharide Vaccine (Injection)

• Dosing schedule:
  • Adults and children ≥10 years: 0.5 ml subcutaneously, 2 doses separated by ≥4 weeks 1
  • Children <10 years: 0.25 ml subcutaneously, 2 doses separated by ≥4 weeks 1
• Age indication: ≥2 years 2
• Efficacy: Prevents 69% of cases in year 1 (high-certainty evidence), 59% in year 2 (moderate-certainty evidence) 2
• Booster: Every 3 years under continued exposure 1
  • Adults/children ≥10 years: 0.5 ml subcutaneously or 0.1 ml intradermally
  • Children 6 months-10 years: 0.25 ml subcutaneously or 0.1 ml intradermally 1

3. Typhoid Conjugate Vaccines (TCVs) - Newer Preferred Option

• Vi-TT (Typbar-TCV): WHO-recommended as preferred vaccine for all ages 2

• Dosing: Single dose 3

• Age indication: ≥6 months 3

• Efficacy: Highly immunogenic with 97% seroconversion and robust long-lasting IgG response 3

• Booster considerations: Immunity may wane after 5 years, especially in children <2 years; booster recommendations under review 4

• Vi-rEPA vaccine: 2 doses

  • Prevents 94% of cases in year 1,87% in year 2 (moderate-certainty evidence) 2
  • Evaluated in children 2-5 years 2

Key Contraindications and Precautions

Oral Ty21a Vaccine

• Absolute contraindications:
  • Immunocompromised persons, including HIV-infected individuals 1
• Pregnancy: No safety data available; avoid use 1
• Side effects: Rare; abdominal discomfort, nausea, vomiting, rash comparable to placebo 1, 2

Parenteral Vi Polysaccharide Vaccine

• Absolute contraindications:
  • History of severe local or systemic reactions to previous dose 1
• Pregnancy: No safety data; theoretically safer than live vaccine for immunocompromised 1
• Side effects:
  • Fever (14-29%), headache (9-30%), severe local pain/swelling (6-40%) 1
  • 13-24% missed work/school due to adverse reactions 1
  • Avoid jet-injector administration - causes increased local reactions 1

Typhoid Conjugate Vaccines

• Safety: Well tolerated with no serious vaccine-attributable adverse events 3
• Compatibility: Can be given with routine infant vaccines including MMR 5

Clinical Pitfalls to Avoid

1. Do not use acetone-inactivated vaccine intradermally - causes severe local reactions 1
2. Do not rely on vaccine alone - vaccines are not 100% effective and protection can be overwhelmed by large inocula; counsel patients on food/water safety 1
3. Ensure all 4 doses of Ty21a are completed - incomplete series reduces efficacy 1
4. Refrigeration is critical for Ty21a - improper storage compromises vaccine viability 1
5. Consider age-specific dosing - children <10 years require reduced volumes of parenteral vaccine 1

Indications for Vaccination

• Travelers to endemic areas with prolonged exposure to potentially contaminated food/water 1
• Intimate household contact with documented typhoid carrier 1
• Microbiology laboratory workers frequently handling S. typhi 1
• Not indicated: Common-source outbreaks, rural summer camps, natural disasters (floods) 1