Can a 12-month-old healthy baby receive the varicella (chickenpox) vaccine?

Varicella Vaccine Administration at 12 Months

Yes, varicella vaccine should be given to a 12-month-old healthy baby—this is the recommended age to initiate routine varicella vaccination. 1, 2

Recommended Vaccination Schedule

All healthy children should receive their first dose of varicella-containing vaccine routinely at age 12-15 months. 1, 2 This timing is strategically chosen to provide protection early while ensuring the child's immune system is sufficiently mature to respond effectively to the live attenuated vaccine. 1

First Dose Administration

• The vaccine is approved for use starting at 12 months of age and should be administered as a 0.5 mL dose given subcutaneously. 2
• At 12 months, a healthy baby meets all criteria for routine vaccination with no special precautions needed. 1, 2
• The vaccine has been demonstrated safe and well-tolerated in this age group, with 96.6% of children aged 12-24 months achieving seroconversion within 6 weeks. 3

Second Dose Timing

• A second dose is routinely recommended at 4-6 years of age (before entering prekindergarten, kindergarten, or first grade). 1, 2
• However, the second dose may be administered earlier, provided the minimum interval of 3 months between doses is maintained. 1, 2
• If the second dose is inadvertently given between 28 days and 3 months after the first dose, it does not need to be repeated. 2

Vaccine Formulation Options

For a 12-month-old, two formulations are available:

• Single-antigen varicella vaccine (Varivax) is approved for ages ≥12 months and can be used at any age. 2
• Combination MMRV vaccine (ProQuad) is approved for children aged 12 months through 12 years. 1, 2

Important Safety Consideration for First Dose

For the first dose in children aged 12-47 months, separate MMR and varicella vaccines are preferred over MMRV (ProQuad) unless parents express preference for MMRV after discussing risks. 2 This recommendation exists because ProQuad carries approximately one additional febrile seizure per 2,300-2,600 doses compared to separate vaccines in children aged 12-23 months. 2

Clinical Efficacy

The two-dose varicella vaccination series provides superior protection:

• After two doses, >99% of children achieve protective antibody levels, compared to only 76-85% after a single dose. 2
• Recipients of two doses are 3.3-fold less likely to experience breakthrough varicella compared to one-dose recipients. 2, 4
• The vaccine efficacy is 98.3% for two doses versus 94.4% for one dose over a 10-year period. 4

Contraindications to Verify

Before administering the vaccine, ensure the 12-month-old does NOT have:

• History of severe anaphylactic reaction to vaccine components (neomycin or gelatin). 2
• Known altered immunity or immunodeficiency. 2
• High-dose systemic corticosteroids (≥2 mg/kg/day prednisone or ≥20 mg/day) for ≥14 days. 2

Common pitfall: Egg allergy is NOT a contraindication, as the varicella vaccine contains no egg protein. 2 Contact dermatitis to neomycin (as opposed to anaphylaxis) is also NOT a contraindication. 2

Safety Profile

The refrigerator-stable formulation of varicella vaccine has demonstrated excellent safety in healthy 12-15 month-old children:

• 47.7% had at least one vaccine-related adverse event, most mild. 5
• Solicited injection-site reactions occurred in 13.0% of children, typically small (≤2.5 cm) and mild. 5
• Pyrexia was the most common systemic adverse event (25.3%). 5
• Varicella-like rashes occurred in only 3.2% of vaccinated children. 5