What are the treatment and prevention options for Varicella-Zoster Virus (VZV) infections?

Treatment and Prevention of Varicella-Zoster Virus (VZV) Infections

Primary Treatment Recommendations

For immunocompromised patients with varicella or disseminated herpes zoster, initiate intravenous acyclovir immediately—within 24 hours of rash onset—to prevent mortality and severe morbidity. 1

Treatment Algorithm by Clinical Presentation

Varicella (Chickenpox)

Immunocompromised Patients:

• Administer IV acyclovir 10 mg/kg every 8 hours for 7-10 days, started within 24 hours of rash onset 2, 1
• Reduce immunosuppressive medications temporarily 2
• Critical pitfall: Acyclovir loses efficacy when initiated >24 hours after rash onset 1

Immunocompetent Adults and Adolescents (≥13 years):

• Oral acyclovir 800 mg four times daily for 5 days if started within 24 hours of rash onset 1, 3
• Alternative: Valacyclovir 20 mg/kg three times daily for 5 days (not to exceed 1 gram three times daily) 4

Pregnant Women:

• For serious complications (e.g., pneumonia): IV acyclovir 1
• For increased risk of moderate-to-severe disease: Oral acyclovir (FDA Category B with reassuring safety data) 1

Immunocompetent Children (<13 years):

• Supportive care only for otherwise healthy children 1
• Oral acyclovir 20 mg/kg four times daily (maximum 800 mg per dose) for 5 days for children with chronic cutaneous disorders (eczema) or pulmonary disorders, if started within 24 hours 1, 3

Herpes Zoster (Shingles)

Uncomplicated Herpes Zoster:

• Oral acyclovir 800 mg five times daily for 7-10 days 2, 3
• Alternative: Oral valacyclovir (superior bioavailability) 2, 4
• Continue treatment at least until all lesions have scabbed 2

Disseminated or Invasive Herpes Zoster:

• IV acyclovir with temporary reduction in immunosuppressive medications 2
• Continue until all lesions have scabbed 2
• Switch to oral antiviral after clinical response, completing 14-21 days total 2

Herpes Simplex Virus (HSV) Infections:

• Superficial HSV 1,2: Oral acyclovir, valacyclovir, or famciclovir until lesions resolve 2
• Systemic HSV 1,2: IV acyclovir with reduction in immunosuppression, then switch to oral therapy for 14-21 days total 2
• Frequent recurrences: Daily suppressive therapy with oral acyclovir or famciclovir 2

Post-Exposure Prophylaxis

VZV-Susceptible Individuals (no history of chickenpox or negative serology):

First-line (within 3 days of exposure):

• Varicella vaccine is >90% effective in preventing disease when given within 3 days of exposure 1
• Do not vaccinate: HIV-infected adults, immunocompromised patients, or pregnant women 2

High-Risk Individuals with Vaccine Contraindications (within 96 hours):

• Varicella-zoster immune globulin (VZIG) for: 2, 1
  • Pregnant women
  • Immunocompromised patients
  • Kidney transplant recipients
  • Newborns whose mothers had varicella 5 days before to 2 days after birth
• If VZIG unavailable or >96 hours post-exposure: 7-day course of oral acyclovir begun 7-10 days after exposure 2

HIV-Infected Children:

• Asymptomatic, non-immunosuppressed children (immunologic category 1): Live attenuated varicella vaccine at 12-15 months 2
• Other HIV-infected children: Do not vaccinate due to risk of disseminated infection 2

Prevention Strategies

Household Contacts:

• Vaccinate seronegative, HIV-negative household contacts (especially children) of susceptible immunocompromised persons to prevent transmission 2

Herpes Zoster Prevention:

• No preventive measures currently available for shingles recurrence in HIV-infected or immunocompromised persons 2
• Vaccination (Zostavax®) boosts VZV-specific cell-mediated immunity in adults >50 years, reducing herpes zoster burden and postherpetic neuralgia 5

Infection Control

Isolation Requirements:

• Isolate patients until all lesions are crusted (typically 5-7 days after rash onset) 1
• Healthcare settings: Airborne and contact precautions 1
• Avoid exposure for susceptible individuals to persons with active chickenpox or shingles 2

Dosage Adjustments for Renal Impairment

Acyclovir Dose Modifications: 3

• Creatinine clearance 10-25 mL/min: 800 mg every 8 hours
• Creatinine clearance 0-10 mL/min: 800 mg every 12 hours
• Hemodialysis: Administer additional dose after each dialysis (60% decrease in plasma concentrations during 6-hour dialysis)

Key Clinical Pitfalls

Timing is Critical:

• Antiviral therapy must be initiated within 24 hours of rash onset for maximum efficacy in most populations 1
• VZIG must be given within 96 hours of exposure 2, 1
• Varicella vaccine is most effective within 3 days of exposure 1

Prophylaxis Errors:

• Acyclovir is not indicated for prophylactic use in otherwise healthy individuals after varicella exposure—vaccination is the method of choice 1
• Do not use live attenuated varicella vaccine in immunocompromised adults or children due to risk of disseminated viral infection 2

Pregnancy Considerations:

• VZIG is recommended for VZV-susceptible pregnant women within 96 hours after exposure 2
• Acyclovir shows no increased birth defect rates compared to general population (FDA Category B) 1