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Varicella Vaccination — SCE Infectious Diseases MCQ

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HardTravel Medicine & VaccinationVaricella VaccinationSCE Infectious Diseases

A 48-year-old man develops fever and a vesicular rash 14 days after receiving a live attenuated varicella vaccine for an occupational health requirement. He has no known immunodeficiency. VZV PCR from a vesicle is positive. Is this vaccine-strain or wild-type VZV?

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Correct answer: C — Genotyping of the VZV isolate can distinguish vaccine strain (Oka) from wild-type VZV

Post-vaccination varicella-like rash occurs in approximately 4% of vaccine recipients and can be caused by either vaccine-strain (Oka) VZV or coincidental wild-type VZV infection. VZV genotyping using restriction fragment length polymorphism (RFLP) or sequencing can distinguish the Oka vaccine strain from wild-type strains. This has implications for infection control — vaccine-strain VZV is less transmissible but still requires contact precautions. Vaccine-strain rash is typically mild with few lesions.

Reference: UKHSA 2024 – Green Book Ch 34: Varicella; PHE 2022 – VZV genotyping