Typhoid vaccination for travellers — DTM&H MCQ

Correct answer: B — Vi capsular polysaccharide injectable vaccine (Typhim Vi)

The correct answer is B, Vi capsular polysaccharide injectable vaccine (Typhim Vi). This inactivated subunit vaccine is given as a single intramuscular or subcutaneous dose and is not a live organism, so it carries no risk of disseminated infection or interaction with the patient's likely long-term anticoagulation for a prosthetic valve, and it can safely be given by the subcutaneous route to avoid intramuscular bleeding risk. A 3 month rural stay in South Asia is a high-risk itinerary for typhoid, so vaccination is clearly indicated, and Vi polysaccharide vaccine is the UK first-line parenteral option recommended in the Green Book for travellers to endemic areas. Its favourable safety profile and lack of interaction with antibiotics or antithrombotics make it the most appropriate choice in a patient with a prosthetic valve who may be on warfarin or another anticoagulant. Why the other options are wrong: E. Live oral Ty21a vaccine (Vivotif): this is a live attenuated organism and, while not absolutely contraindicated in a well non-immunosuppressed patient, it is inactivated by concurrent antibiotics and by antimalarials such as proguanil, making it logistically less reliable for a long, complex rural itinerary; the injectable Vi vaccine avoids this interaction entirely. A. Combined hepatitis A and typhoid vaccine only: this fixes the typhoid component to a specific hepatitis A schedule and is not the recommended default when hepatitis A immunity status is unknown or already covered separately, so it should not be assumed as the primary typhoid choice. D. Whole-cell killed parenteral vaccine: this older formulation is no longer manufactured or used in the UK because of its high reactogenicity (fever, local reactions) compared with the purified Vi polysaccharide vaccine. C. No typhoid vaccine is recommended for this patient: incorrect, since prolonged rural travel in South Asia is a recognised high-risk exposure for typhoid and vaccination is specifically advised regardless of cardiac valve status. Key point: for travellers needing typhoid protection who should avoid live vaccines or have anticoagulation or interaction concerns, the injectable Vi capsular polysaccharide vaccine is the preferred single-dose option in UK travel health practice.

Reference: UK Health Security Agency, Immunisation against infectious disease (the Green Book), Chapter 33: Typhoid, updated 2022, https://www.gov.uk/government/publications/typhoid-the-green-book-chapter-33