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Rifaximin and Rifampicin Resistance — SCE Infectious Diseases MCQ

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HardAntimicrobial StewardshipRifaximin and Rifampicin ResistanceSCE Infectious Diseases

A 46-year-old allogeneic stem-cell recipient taking tacrolimus has prolonged household exposure to chickenpox. Childhood chickenpox is recalled, but quantitative VZV IgG is 92 mIU/mL. The first exposure day was three days ago; renal function is normal. What is the recommended UK post-exposure regimen?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — Aciclovir 800 mg orally four times daily from day 7 through day 14 post-exposure

Explanation lettering: E = shown as A · C = shown as B · A = shown as C · B = shown as E

C is correct. In immunosuppressed people, recalled disease or vaccination does not reliably establish protection; quantitative VZV IgG below 150 mIU/mL after a significant exposure meets the UKHSA susceptibility threshold. Oral antiviral PEP is first choice and is timed to cover the secondary viraemic phase: for adults, aciclovir 800 mg four times daily from day 7 to day 14 after the first exposure (valaciclovir 1 g three times daily is an alternative). Intramuscular VZIG is no longer available in the UK, immediate antiviral dosing is less effective than day-7 initiation, and any detectable antibody is not an adequate threshold in this immunosuppressed patient.

Reference: UKHSA: varicella or shingles post-exposure prophylaxis: https://www.gov.uk/government/publications/post-exposure-prophylaxis-for-chickenpox-and-shingles/guidelines-on-post-exposure-prophylaxis-pep-for-varicella-or-shingles-january-2023