Should chemotherapy be stopped and varicella (chickenpox) immunoglobulin be administered to a child undergoing chemotherapy who has been exposed to varicella due to a sibling's infection?

Management of Chemotherapy and Varicella Immunoglobulin After Household Exposure

Do not stop chemotherapy, but administer varicella-zoster immune globulin (VariZIG) immediately—ideally within 96 hours but up to 10 days after exposure—to this immunocompromised child who has been exposed to varicella through household contact with their sibling. 1

Immediate Actions Required

Administer VariZIG Without Delay

• VariZIG should be given as soon as possible after exposure, ideally within 96 hours (4 days) for maximum effectiveness, though it can be administered up to 10 days post-exposure 1
• The household setting represents the highest-risk exposure scenario, with 65-100% attack rates in susceptible household contacts 1, 2
• Dosing: 125 units/10 kg body weight, up to maximum 625 units (five vials), minimum dose 125 units 1
• VariZIG can be obtained 24 hours/day from FFF Enterprises at 1-800-843-7477 1

Continue Chemotherapy

• There is no guideline recommendation to stop chemotherapy after varicella exposure 1
• The evidence shows that immunocompromised children on chemotherapy who develop varicella should be hospitalized and treated with intravenous acyclovir, but chemotherapy interruption is a consequence of illness, not a preventive measure 3
• Stopping chemotherapy prophylactically would compromise cancer treatment without proven benefit for varicella prevention 1

Rationale for This Approach

Why VariZIG is Critical

• In immunocompromised children who received VariZIG within 96 hours, only 1 in 5 exposures resulted in clinical varicella, and 1 in 20 resulted in subclinical disease—compared to 65-85% attack rates in historical controls 1
• Among those who developed illness despite VariZIG, disease severity (percentage with >100 lesions or complications) was significantly reduced 1
• Children on chemotherapy are at high risk for visceral dissemination, fulminant hepatitis, disseminated intravascular coagulation, and fatal outcomes 4, 5

Why Chemotherapy Should Continue

• The 2013 IDSA guidelines emphasize that varicella vaccination (not chemotherapy cessation) is the appropriate preventive strategy, and this should ideally occur before immunosuppression begins 1
• Post-exposure management focuses on passive immunization with VariZIG, not chemotherapy modification 1
• Chemotherapy interruption would only be warranted if the child develops active varicella infection requiring treatment 3

Critical Monitoring and Follow-Up

Extended Incubation Period

• VariZIG may extend the varicella incubation period from the typical 10-21 days to >28 days 1
• Monitor the child closely for 28+ days after exposure for any signs of varicella 1

If Varicella Develops Despite VariZIG

• Immediate hospitalization for intravenous acyclovir 30 mg/kg/day (or standard dosing per protocol) 3, 6
• Consider high-dose intravenous immunoglobulin (IVIG) in addition to acyclovir if dissemination occurs, as this combination has rescued children with multiple organ failure 4, 5
• Chemotherapy will need to be held during active infection and treatment 3

Important Caveats

VariZIG Limitations

• VariZIG is not 100% effective—prophylaxis failure can occur even with appropriate administration 6
• Protection lasts approximately 3 weeks (one half-life of immunoglobulin); if re-exposed >3 weeks later, another full dose is needed 1
• Patients receiving monthly high-dose IGIV (>400 mg/kg) within 3 weeks of exposure likely don't need VariZIG, but this doesn't apply to most chemotherapy patients 1

Sibling Management

• The infected sibling should be isolated from the immunocompromised child until all lesions are crusted 2
• Consider vaccinating other susceptible household contacts at time of cancer diagnosis to prevent future exposures 3

Not a Treatment for Active Disease

• VariZIG is for post-exposure prophylaxis only—it does not treat active varicella or prevent disseminated zoster 1
• If the child already has symptoms or lesions, VariZIG is not indicated; proceed directly to acyclovir treatment 1