At what age is the varicella (chickenpox) vaccine recommended?

Varicella Vaccine Age Requirements

The first dose of varicella vaccine should be administered at 12-15 months of age, with the second dose routinely given at 4-6 years of age (before kindergarten or first grade entry). 1

Primary Vaccination Schedule

First Dose Timing

• All healthy children should receive their first dose of varicella-containing vaccine routinely at 12-15 months of age 1
• The vaccine is approved for use starting at 12 months of age 1
• Research demonstrates that vaccine effectiveness does not differ based on whether children are vaccinated at 12-14 months versus 15-18 months of age, supporting the current 12-15 month recommendation 2

Second Dose Timing

• The second dose is routinely recommended at 4-6 years of age (before entering prekindergarten, kindergarten, or first grade) 1
• However, the second dose may be administered at an earlier age, provided the minimum interval between doses is met 1
• This timing is strategically chosen because varicella incidence and outbreaks are higher among elementary school-aged children compared to preschool-aged children 1

Minimum Intervals Between Doses

Children 12 Months Through 12 Years

• Minimum interval: 3 months between first and second doses 1, 3
• This 3-month interval is based on the design of clinical studies evaluating two-dose regimens in this age group 1, 3
• Important exception: If the second dose is inadvertently administered between 28 days and 3 months after the first dose, it is considered valid and does not need to be repeated 1, 3

Persons 13 Years and Older

• Minimum interval: 4 weeks (28 days) between doses 1, 3
• Adolescents and adults without evidence of immunity should receive two 0.5-mL doses separated by at least 28 days 1
• Only single-antigen varicella vaccine (not MMRV) is licensed for use in persons ≥13 years 1

Rationale for Two-Dose Schedule

Superior Protection

• Two doses provide 98% vaccine efficacy compared to 94% for a single dose 3
• Recipients of two doses are 3.3-fold less likely to experience breakthrough varicella compared to single-dose recipients 3
• After two doses, >99% of children achieve protective antibody levels, compared to only 76-85% after a single dose 3
• Seroconversion rates are 98.2% after one dose versus 99.9% after two doses 4

Public Health Impact

• The two-dose schedule reduces breakthrough cases and outbreaks among school-aged populations 3
• School outbreaks have demonstrated that single-dose vaccine effectiveness of 72-85% is insufficient to control transmission in highly vaccinated populations 1
• By 2012, two-dose coverage among 7-year-olds reached 79.9%-92.0% in sentinel sites, approaching MMR coverage levels 5

School Entry Requirements

• As of 2012, 36 states (including DC) had implemented two-dose varicella vaccination elementary school entry requirements, up from only 4 states in 2007 5
• All children entering school should have received two doses of varicella-containing vaccine or have other evidence of immunity 1
• The high transmission risk in school settings necessitates this requirement 1

Available Vaccine Formulations

For Children 12 Months Through 12 Years

• Monovalent varicella vaccine (Varivax): Approved for ages ≥12 months 1
• Combination MMRV vaccine (ProQuad): Approved only for ages 12 months through 12 years 1
• Combination vaccines are preferred when all components are indicated to minimize the number of injections 1

For Persons ≥13 Years

• Only single-antigen varicella vaccine may be used 1
• MMRV is not licensed for this age group 1

Common Pitfalls to Avoid

• Do not delay the first dose beyond 15 months without valid contraindications, as this increases the period of susceptibility 1
• Do not repeat the second dose if it was inadvertently given between 28 days and 3 months after the first dose in children <13 years 1, 3
• Do not accept parental self-reporting of varicella disease as adequate documentation of immunity in the vaccine era, as it has become less reliable 1
• Ensure written documentation of vaccination dates; only doses with written documentation should be considered valid 1, 6
• Do not administer live virus vaccines less than 28 days apart unless given on the same day, as this may impair immune response 6

Special Populations Requiring Priority Vaccination

Adults at increased risk who lack evidence of immunity should receive special consideration for two-dose vaccination 1:

• Healthcare personnel
• Household contacts of immunocompromised persons
• Teachers and daycare employees
• College students and military personnel
• Nonpregnant women of childbearing age
• International travelers