Post-Exposure Prophylaxis for Shingles (Herpes Zoster)
Patients who do not have evidence of immunity to varicella should receive post-exposure prophylaxis with VariZIG as soon as possible (but within 10 days) after exposure to a person with varicella or shingles. 1, 2
Assessment of Immunity
Before determining appropriate post-exposure prophylaxis, assess evidence of immunity:
- Documented history of varicella disease
- Laboratory evidence of immunity or confirmed disease
- Documentation of age-appropriate vaccination
- Birth in the United States before 1980 (only for immunocompetent, non-pregnant patients)
VariZIG Administration
- Administer VariZIG as soon as possible after exposure
- Effective when given within 10 days post-exposure (previously limited to 96 hours) 2, 3
- Dosage: 125 IU/10 kg body weight (maximum 625 IU), administered intramuscularly 2
Dosing by Weight:
| Patient Weight | Recommended Dose |
|---|---|
| ≤2.0 kg | 62.5 IU (0.5 vial) |
| 2.1-10.0 kg | 125 IU (1 vial) |
| >10.0 kg | 125 IU/10 kg body weight, up to maximum 625 IU (5 vials) |
High-Risk Populations Requiring VariZIG
- Immunocompromised individuals without evidence of immunity
- Pregnant women without evidence of immunity
- Newborns whose mothers developed varicella between 7 days before and 7 days after delivery
- Premature infants (<28 weeks gestation or birth weight ≤1,000 g) regardless of maternal history
- Hospitalized premature infants (≥28 weeks gestation) whose mothers lack evidence of immunity
Post-Exposure Vaccination
For healthy, non-pregnant individuals ≥12 months of age without evidence of immunity:
- Administer varicella vaccine within 3-5 days of exposure 2
- Effectiveness: 70-90% in preventing infection or reducing severity
- Consider second dose for adults and children who have received one dose previously (if ≥4 weeks since first dose)
Alternative Prophylaxis
When VariZIG is unavailable or administration window has passed:
- Acyclovir prophylaxis may be considered: 20 mg/kg body weight (maximum 800 mg) per dose orally 4 times daily for 5-7 days 2, 4
- Valacyclovir may also be considered as an alternative, though evidence is limited 4
Monitoring After Exposure
- Monitor closely for 28 days for development of varicella 2
- VariZIG can extend the incubation period from 10-21 days to >28 days
- Initiate antiviral treatment immediately if symptoms develop
Healthcare Worker Management
For healthcare workers exposed to shingles:
- Those with 2 doses of vaccine: monitor daily during days 8-21 post-exposure
- Those with 1 dose: receive second dose within 3-5 days (if ≥4 weeks since first dose)
- Unvaccinated without immunity: furlough during days 8-21 post-exposure and vaccinate
- Those with contraindications to vaccination: receive VariZIG and extend work restriction to 28 days
Efficacy and Safety
- Recent data shows VariZIG administration is associated with low rates of varicella in high-risk individuals 5, 6
- Similar efficacy when administered ≤96 hours vs. >96 hours (up to 10 days) post-exposure 6
- Generally well-tolerated with minimal adverse effects (pain at injection site, headache) 2
- One serious adverse event (serum sickness) was reported in a child with oncologic immunodeficiency 5
Important Considerations
- VariZIG is the preferred prophylaxis for high-risk individuals
- Patients receiving monthly high-dose IGIV (>400 mg/kg) within 3 weeks before exposure likely do not require VariZIG
- A repeated dose of VariZIG may be necessary if new exposure occurs >3 weeks after initial dose
- For patients eligible for vaccination, varicella vaccine should be administered ≥5 months after VariZIG administration