What is the recommended repeat interval for the typhoid (Salmonella Typhi) vaccine?

Typhoid Vaccine Booster Recommendations

For typhoid vaccines, the recommended booster interval is every 3 years for the parenteral inactivated vaccine and every 5 years for the oral live-attenuated Ty21a vaccine. 1

Types of Typhoid Vaccines and Booster Schedules

Parenteral Inactivated Vaccine (Vi polysaccharide)

• Booster doses should be given every 3 years to persons with continued or repeated exposure to S. typhi 1
• A single booster dose is sufficient even if more than 3 years have elapsed since the prior vaccination 1
• The booster can be administered subcutaneously (0.5 mL) or intradermally (0.1 mL) 1
• The FDA-approved Vi polysaccharide vaccine recommends reimmunization consisting of a single dose for US travelers every two years under conditions of repeated or continued exposure 2

Oral Live-Attenuated Ty21a Vaccine

• The manufacturer recommends revaccination with the entire four-dose series every 5 years 1
• Long-term efficacy studies have shown continued protection for at least 5-7 years after vaccination 3
• The four-dose regimen has demonstrated 78% protection over five years of follow-up with the liquid formulation 3
• The enteric-coated capsule formulation provided 62% protection over seven years of follow-up 3

Indications for Typhoid Vaccination

• Vaccination is indicated for travelers to areas with recognized risk of typhoid exposure, particularly in developing countries in Latin America, Asia, and Africa 4
• Other groups requiring vaccination include:
  • Persons with intimate exposure to documented typhoid carriers 1
  • Workers in microbiology laboratories who frequently work with S. typhi 1
• Routine vaccination of sewage sanitation workers is only warranted in areas with endemic typhoid fever 1

Efficacy of Typhoid Vaccines

• The parenteral Vi polysaccharide vaccine prevents around two-thirds of typhoid cases in the first year (69% efficacy) and about 59% in the second year 5
• The oral Ty21a vaccine prevents approximately 50% of typhoid cases during the first three years after vaccination 5
• The newer typhoid conjugate vaccines (TCV) have shown higher efficacy (83% at 2 years post-immunization) compared to traditional vaccines 6

Important Considerations and Precautions

• Even after vaccination, careful selection of food and drink remains essential as vaccines are not 100% effective 4
• The Vi polysaccharide vaccine may cause swelling and pain at the injection site but generally does not increase fever or erythema compared to placebo 5
• The oral Ty21a vaccine may cause mild adverse events such as fever but generally does not cause more vomiting, diarrhea, nausea, or abdominal pain than placebo 5
• Typhoid vaccination is not recommended for use in areas of natural disaster 1

Special Populations

• The oral Ty21a vaccine is not recommended for children <6 years of age or immunocompromised persons 1
• Safety and effectiveness of the Vi polysaccharide vaccine have been established in children 2 years of age and older 2
• For children below 2 years of age, safety and effectiveness have not been established for the Vi polysaccharide vaccine 2

Remember that the booster schedule should be strictly followed for individuals with continued or repeated exposure to ensure ongoing protection against typhoid fever.