What if the patient did not have a diagnosis of varicella (chicken pox)?

Management When Patient Did Not Have Chickenpox

If the patient never had chickenpox (varicella-naive), they are at significant risk for severe primary varicella infection if exposed, particularly if immunocompromised, and require immediate vaccination if not on immunosuppressive therapy or urgent post-exposure prophylaxis if exposure has occurred. 1

Screening and Risk Assessment

Screen all patients by history for prior chickenpox, shingles, or receipt of two doses of varicella vaccine. 1

• Patients without a clear history of any of these should be tested for VZV IgG antibody to determine immunity status 1
• Between 65-70% of adult patients are seropositive for VZV, meaning 30-35% remain susceptible 1
• Seronegative (varicella-naive) patients face substantially higher risk of severe complications including pneumonia, hepatitis, encephalitis, and hemorrhagic disorders 1

Vaccination Strategy for Varicella-Naive Patients

Complete the two-dose varicella vaccine series at least 3 weeks prior to starting any immunomodulator or immunosuppressive therapy. 1

• The vaccine is a live attenuated virus and cannot be given to patients already on immunosuppressive therapy due to risk of disseminated viral infection 2
• Two doses provide protection from severe chickenpox and should be given 4-8 weeks apart 3
• After vaccination, subsequent immunosuppressive therapy can only be commenced after waiting at least 3 weeks 1
• If already on immunosuppression, vaccination requires a 3-6 month cessation of all immunosuppressive therapy before and after administration 1

Exception for Low-Dose Immunosuppression

• According to CDC guidelines, therapy with low-dose methotrexate (≤0.4 mg/kg/week), azathioprine (≤3.0 mg/kg/day), or 6-mercaptopurine (≤1.5 mg/kg/day) are not considered sufficiently immunosuppressive to contraindicate zoster vaccine administration 1

Post-Exposure Prophylaxis Protocol

If a varicella-naive patient is exposed to chickenpox, administer Varicella-Zoster Immune Globulin (VZIG) within 96 hours of exposure. 2

• VZIG is first-line prophylaxis for high-risk individuals, including immunocompromised patients 2
• VZIG may prolong the incubation period to 28 days, requiring extended monitoring 2
• If VZIG is unavailable, consider acyclovir 20 mg/kg (maximum 800 mg) four times daily for 5-7 days, initiated 7-10 days after exposure 2
• Post-exposure vaccination within 3-5 days may modify disease if infection has not yet occurred, but only in non-immunocompromised patients 2

Management of Active Chickenpox in Varicella-Naive Patients

Chickenpox is more severe and potentially life-threatening in adults and immunocompromised patients, requiring aggressive antiviral therapy. 1

Treatment Regimen

• Immunocompromised patients require immediate intravenous acyclovir 10 mg/kg every 8 hours 2
• Immunocompetent adults should receive oral acyclovir 800 mg orally 4-5 times daily for 7-10 days 2
• Children <45 kg should receive 20 mg/kg (maximum 400 mg/dose) 3-4 times daily for 5-10 days 2

Critical Management Steps

• Discontinue immunomodulator therapy immediately during active chickenpox infection 1, 2
• Do not commence immunomodulator therapy during active infection 1
• Immunomodulator therapy can only be reintroduced after all vesicles have crusted over and fever has resolved 1
• In a review of VZV in IBD patients, five of 20 cases of varicella proved fatal, highlighting the severity in immunocompromised populations 1

Isolation and Infection Control

Isolate patients with active chickenpox until all lesions have crusted over. 2

• Healthcare workers without immunity who are exposed should receive post-exposure vaccination and be furloughed from days 10-21 after exposure 2
• Household contacts of susceptible immunocompromised individuals should be vaccinated if seronegative 2

Common Pitfalls to Avoid

• Never assume immunity based on age alone—always verify history or serology 1
• Never administer live varicella vaccine to patients already on immunosuppressive therapy—this can cause disseminated viral infection 2
• Never delay VZIG administration beyond 96 hours post-exposure—efficacy drops significantly after this window 2
• Never continue immunosuppressive therapy during active varicella infection in severe cases—this substantially increases mortality risk 1, 2