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Difficulty: HardImmunizations and Vaccine-Preventable Diseases

A 5-year-old girl is brought to the pediatrician by her parents due to a potential varicella exposure. Yesterday, she spent 4 hours playing indoors with her 6-year-old cousin, who subsequently developed a low-grade fever and a diffuse vesicular rash earlier today. The cousin has just been diagnosed with chickenpox. The patient has a history of acute lymphoblastic leukemia, diagnosed one year ago, and she is currently on a maintenance chemotherapy regimen consisting of daily 6-mercaptopurine and weekly methotrexate. A review of her immunization registry shows she completed all routine infancy vaccines, including her first doses of the measles-mumps-rubella and varicella vaccines at 12 months of age. No further vaccines have been administered since her cancer diagnosis. The patient feels well today, and her physical examination is completely normal. Which of the following is the most appropriate next step in the management of this patient?

  1. A
    Measure serum varicella IgG antibodies
  2. B
    Prescribe a 7-day course of prophylactic oral acyclovir
  3. Administer varicella-zoster immune globulinAnswer
  4. D
    Administer the live-attenuated varicella vaccine
  5. E
    Reassure the parents and monitor the patient closely for a rash

Answer

The most appropriate next step in management is to administer varicella-zoster immune globulin.
The correct answer is to administer varicella-zoster immune globulin (VZIG). This patient has had a significant exposure to the varicella-zoster virus (defined as face-to-face contact, playing indoors for >1 hour, or household contact). She is at high risk for severe, disseminated varicella due to her immunocompromised state resulting from maintenance chemotherapy for acute lymphoblastic leukemia. Although she received one dose of the varicella vaccine at age 12 months, a single dose does not provide reliable immunity, especially in a patient with active immunosuppression. Therefore, she lacks definitive evidence of immunity. For severely immunocompromised individuals without evidence of immunity who have significant VZV exposure, post-exposure prophylaxis with VZIG is indicated as soon as possible (ideally within 96 hours, but up to 10 days post-exposure) to prevent or attenuate the disease.

Step-by-Step Solution

1
Evaluate the risk level of the exposure.
The patient had 4 hours of indoor contact with a contagious individual, qualifying as a significant exposure.
Determining the exposure severity is required to assess the need for post-exposure prophylaxis.
2
Assess the patient's immune status and susceptibility.
The patient is on maintenance chemotherapy, rendering her severely immunocompromised. Her single prior dose of the varicella vaccine is insufficient to confer reliable immunity in this state.
Immune status determines both the risk of severe disease and the safety of clinical interventions, such as live vaccines.
3
Determine the optimal post-exposure prophylaxis strategy.
Passive immunization with varicella-zoster immune globulin is required as soon as possible.
Severely immunocompromised patients lacking full evidence of immunity must receive passive immunization to prevent life-threatening disseminated infection.

Key Concept

Post-exposure prophylaxis for varicella-zoster virus in immunocompromised patients
Estimated Time:1m 30s
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Topics

Immunizations and Vaccine-Preventable Diseases

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