What is the recommended interval between the first and second doses of the varicella (chickenpox) vaccine?

Varicella Vaccine Dosing Interval

For children aged 12 months through 12 years, the minimum interval between varicella dose #1 and dose #2 is 3 months, though a dose given as early as 28 days after the first is considered valid and does not need repeating. 1, 2

Age-Specific Minimum Intervals

Children 12 Months Through 12 Years

• The recommended minimum interval is 3 months between the first and second varicella vaccine doses 1, 2
• This 3-month interval is based on the design of clinical trials that evaluated two-dose regimens in this age group 1
• If the second dose is inadvertently administered at least 28 days (but less than 3 months) after the first dose, it is considered valid and does not need to be repeated 1, 2
• The routine schedule recommends the first dose at 12-15 months and the second dose at 4-6 years (before school entry), though earlier administration is acceptable if the minimum interval is met 1, 2

Persons Aged 13 Years and Older

• The minimum interval between doses is 4 weeks (28 days) for adolescents and adults 1, 3
• The recommended interval is 4-8 weeks apart for this age group 1, 3
• Only single-antigen varicella vaccine (not MMRV) may be used in persons ≥13 years 3

Clinical Rationale for Two-Dose Schedule

The two-dose regimen provides substantially superior protection compared to a single dose:

• Vaccine efficacy increases from 94% with one dose to 98% with two doses 2
• Recipients of two doses are 3.3-fold less likely to experience breakthrough varicella compared to single-dose recipients 2
• After two doses, >99% of children achieve protective antibody levels, compared to only 76-85% after a single dose 2

Important Considerations

Timing with Other Live Vaccines

• MMR and varicella vaccines must either be given on the same day OR separated by at least 28 days 4
• Administering live virus vaccines less than 28 days apart (unless simultaneous) may result in impaired immune response 4

Common Pitfalls to Avoid

• Do not restart the vaccine series regardless of time elapsed—simply complete the two-dose series with appropriate intervals 2
• Do not use MMRV vaccine for persons ≥13 years, as it is only licensed for children 12 months through 12 years 2, 3
• The 28-day minimum for children 12 months-12 years is a grace period for inadvertent early administration, not the recommended interval 1, 2

School Entry Requirements

• All children entering school should have received two doses of varicella vaccine or have other evidence of immunity 1, 2
• As of 2012,36 states had implemented two-dose varicella vaccination school entry requirements, resulting in coverage levels of 79.9%-92.0% among 7-year-olds 5