Varicella Post-Exposure Prophylaxis in the Immunocompromised Child
A 5-year-old boy with acute lymphoblastic leukaemia is on maintenance chemotherapy and has been receiving prednisolone 2 mg/kg per day for 6 weeks. Two days ago he played with a cousin who developed a vesicular rash the following morning. He is afebrile with no rash, his lymphocyte count is 0.4 × 10⁹/L, and varicella zoster virus IgG is negative. Which of the following is the most appropriate management?
- A.Live attenuated varicella vaccine
- B.Varicella zoster immunoglobulinCorrect
- C.Reassurance and routine follow-up
- D.Hospital admission for respiratory isolation
Explanation
A seronegative, significantly immunocompromised child who has had close contact with chickenpox is at high risk of severe disseminated varicella with pneumonitis, hepatitis, coagulopathy and death, so passive immunization is required. Varicella zoster immunoglobulin should be given as soon as possible and within 10 days of exposure, ideally within 96 hours, and it substantially attenuates the illness. This child qualifies on two grounds: active chemotherapy for leukaemia and high-dose systemic corticosteroid therapy of 2 mg/kg per day for more than 14 days, both of which define significant immunosuppression. Live attenuated varicella vaccine is contraindicated in this setting because it can itself cause disseminated vaccine-strain disease in a profoundly immunosuppressed host, and post-exposure vaccination is only appropriate for healthy susceptible contacts within 3 to 5 days. Doing nothing is unsafe given the mortality of varicella in the immunocompromised. Admission for isolation is not a prophylactic measure and does nothing to prevent infection already acquired. Where varicella zoster immunoglobulin is unavailable, intravenous immunoglobulin or oral aciclovir started around day 7 after exposure is an accepted alternative. Other groups eligible for varicella zoster immunoglobulin include susceptible pregnant women, neonates whose mothers develop varicella from 5 days before to 2 days after delivery, and preterm infants with significant exposure.
Why each option
- A.
- Live varicella vaccine is contraindicated during chemotherapy and high-dose steroid therapy and could itself cause disseminated infection.
- B.
- Correct. Varicella zoster immunoglobulin within 10 days, ideally within 96 hours, is the standard post-exposure prophylaxis for susceptible immunocompromised children.
- C.
- Observation alone risks fatal disseminated varicella in a seronegative child on chemotherapy and high-dose steroids.
- D.
- Isolation protects other patients but confers no protection to this child against an exposure that has already occurred.
Reference: AAP Red Book, 2024, Varicella-Zoster Virus Infections
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