What is the recommended post-exposure prophylaxis for varicella zoster in non-immune individuals?

Post-Exposure Prophylaxis for Varicella Zoster in Non-Immune Individuals

For non-immune individuals exposed to varicella zoster virus, VariZIG (varicella zoster immune globulin) should be administered as soon as possible after exposure and within 10 days for high-risk individuals, while varicella vaccine is recommended for healthy non-immune individuals within 3-5 days of exposure. 1

Assessing Immunity Status

Before determining the appropriate post-exposure prophylaxis, it's essential to assess immunity status:

• Evidence of immunity includes:
  • Documentation of age-appropriate varicella vaccination
  • Laboratory evidence of immunity or laboratory confirmation of disease
  • Birth in the U.S. before 1980 (except for healthcare workers and pregnant women)
  • History of varicella disease diagnosed by a healthcare provider
  • History of herpes zoster diagnosed by a healthcare provider

Post-Exposure Prophylaxis Options

1. VariZIG (Varicella Zoster Immune Globulin)

VariZIG is indicated for high-risk individuals who lack evidence of immunity and for whom varicella vaccine is contraindicated 1:

• Timing: Should be administered as soon as possible after exposure, ideally within 96 hours (4 days) for greatest effectiveness, but can be given up to 10 days post-exposure 1, 2
• Dosage: 125 units/10 kg of body weight, up to a maximum of 625 units (five vials), with a minimum dose of 125 units 1
• High-risk groups eligible for VariZIG:
  • Immunocompromised patients without evidence of immunity
  • Pregnant women without evidence of immunity
  • Newborns of mothers with varicella onset within 5 days before or 2 days after delivery
  • Premature infants (<28 weeks gestation or ≤1000 g birth weight)
  • Premature infants ≥28 weeks gestation whose mothers lack evidence of immunity

2. Varicella Vaccine

For healthy, non-immune individuals who are eligible for vaccination:

• Should be administered within 3-5 days of exposure
• Can prevent or significantly modify disease if given within this timeframe
• Not recommended for pregnant women, severely immunocompromised individuals, or infants <12 months

3. Antiviral Therapy (Acyclovir)

When VariZIG is unavailable or the window for administration has passed:

• Can be considered for immunocompromised patients when VariZIG cannot be administered
• Typically 80 mg/kg/day divided into 4 doses (maximum 800 mg 4 times daily) for 7 days 3
• Should begin 7-10 days after exposure

Effectiveness of Post-Exposure Prophylaxis

• VariZIG: Studies show low rates of varicella development in high-risk individuals receiving VariZIG, with similar effectiveness whether administered within 96 hours or up to 10 days post-exposure 2

  • Incidence of varicella after VariZIG: 4.5% in immunocompromised participants, 7.3% in pregnant women, and 11.5% in infants 2
  • When varicella does develop, it's typically milder than in untreated cases 4

• Varicella vaccine: Post-exposure vaccination has been shown to reduce disease rate and severity in otherwise healthy children

Important Clinical Considerations

• VariZIG may extend the incubation period of varicella from 10-21 days to >28 days, which should be considered during monitoring 1
• Patients receiving monthly high-dose IVIG (>400 mg/kg) within 3 weeks before exposure likely don't require VariZIG 1
• VariZIG is not effective for treating established varicella or herpes zoster infection
• For subsequent exposures occurring >3 weeks after a dose of VariZIG, another full dose should be administered if the patient remains at high risk 1

Common Pitfalls to Avoid

1. Delayed administration: Efficacy decreases with time, so administer prophylaxis as soon as possible after exposure
2. Overlooking bone marrow transplant recipients: These patients should be considered non-immune regardless of previous history of varicella or vaccination 1
3. Misinterpreting exposure risk: Significant exposure includes face-to-face indoor contact (not transient), household contact, or hospital contact (sharing room with infectious patient)
4. Failing to recognize that VariZIG reduces severity but doesn't prevent all cases: Patients should still be monitored for breakthrough infection

By following these evidence-based recommendations, clinicians can effectively manage varicella zoster virus exposures in non-immune individuals and reduce the risk of severe disease and complications.