Varicella (Varivax) Dosing Recommendations
All individuals receiving Varivax should get 0.5 mL per dose administered subcutaneously, with the number of doses and timing dependent on age at first vaccination. 1
Dose Volume and Route
- Each dose of Varivax is 0.5 mL administered subcutaneously (or intramuscularly if needed) 1
- The subcutaneous route is preferred, though inadvertent intramuscular administration does not require revaccination 2
Pediatric Dosing (12 Months Through 12 Years)
Children in this age group require two 0.5 mL doses separated by at least 3 months. 3, 1
First Dose Timing
- Administer the first dose at 12-15 months of age 3, 4
- May be given anytime from 12 months through 12 years of age 1
Second Dose Timing
- Routinely recommended at 4-6 years of age (before entering kindergarten or first grade) 3, 4
- Can be administered earlier if the minimum 3-month interval is maintained 3, 4
- Important caveat: If the second dose is inadvertently given between 28 days and 3 months after the first dose, it does not need to be repeated 3, 4
Rationale for Two-Dose Schedule
- Two doses provide 98% vaccine efficacy versus 94% for one dose 3, 4
- Recipients of two doses are 3.3-fold less likely to develop breakthrough varicella compared to one dose 3, 4
- After two doses, >99% of children achieve protective antibody levels 4
- Two-dose vaccination provides 100% efficacy against severe disease 3
Adolescent and Adult Dosing (≥13 Years)
Individuals 13 years and older require two 0.5 mL doses separated by at least 4 weeks (28 days). 3, 1
- This shorter interval (4 weeks vs. 3 months for children) applies to all adolescents and adults without evidence of immunity 3, 4
- Only monovalent varicella vaccine (Varivax) may be used in this age group 4
Vaccine Formulation Options
- Varivax (monovalent): Approved for ages ≥12 months, including adolescents and adults 3, 4, 1
- ProQuad (MMRV combination): Approved only for ages 12 months through 12 years 3, 4
Reconstitution and Administration
- Use only the supplied sterile diluent free of preservatives, antiseptics, and detergents 1
- Withdraw entire volume of diluent and slowly inject into lyophilized vaccine vial 1
- Gently agitate to dissolve completely; reconstituted vaccine should be clear, colorless to pale yellow 1
- Critical timing: Administer immediately after reconstitution; discard if not used within 30 minutes 1
- Do not freeze reconstituted vaccine 1
- Do not combine with any other vaccine through reconstitution or mixing 1
Common Pitfalls to Avoid
- Do not delay the first dose beyond 15 months without reason—vaccination at 12-15 months is equally effective as later vaccination 5
- Do not repeat a second dose given at 28 days to 3 months after the first dose in children 3
- Do not use MMRV (ProQuad) in patients ≥13 years old 4
- Do not use preservatives or antiseptics when reconstituting, as these inactivate the vaccine virus 1