Second Varicella Vaccine Timing
The second varicella vaccine dose should be administered at age 4-6 years, typically before entering prekindergarten, kindergarten, or first grade. 1, 2
Standard Two-Dose Schedule
- First dose: Administer at 12-15 months of age 2
- Second dose: Administer at 4-6 years of age (before school entry) 1, 2
The 4-6 year timing is strategically chosen because varicella incidence and outbreaks are significantly higher among elementary school-aged children compared to preschool-aged children. 2
Flexibility in Timing
The second dose may be given earlier than 4-6 years if needed, provided minimum intervals are met: 2
- For children 12 months through 12 years: Minimum interval of 3 months between doses 2
- For persons 13 years and older: Minimum interval of 4 weeks (28 days) between doses 2
If the second dose is inadvertently administered between 28 days and 3 months after the first dose in children, it does not need to be repeated. 2
Clinical Rationale for Two Doses
The two-dose schedule provides substantially superior protection compared to a single dose:
- Vaccine efficacy: 98% with two doses versus 94% with one dose 2
- Breakthrough infection risk: Recipients of two doses are 3.3-fold less likely to develop breakthrough varicella 2
- Seroprotection rates: >99% of children achieve protective antibody levels after two doses, compared to 76-85% after a single dose 2
School Entry Requirements
All children entering elementary school should have received two doses of varicella-containing vaccine or have other evidence of immunity, as this is now required in 36 states as of 2012 (up from only 4 states in 2007). 3
Catch-Up Vaccination
For children who have never received varicella vaccine (such as a 7-year-old), administer the first dose immediately and schedule the second dose 3 months later, though the minimum acceptable interval is 28 days. 2 There is no need to restart the series regardless of time elapsed. 2