Can varicella vaccine brands be interchanged?

Can Varicella Vaccine Brands Be Interchanged?

Yes, varicella vaccine brands are fully interchangeable—you can use any available varicella-containing vaccine (Varivax or ProQuad) to complete the vaccination series without compromising efficacy or safety. 1

Evidence Supporting Interchangeability

The ACIP General Best Practices guidelines explicitly state that all brands of varicella vaccines are interchangeable within their respective series, similar to hepatitis B and hepatitis A vaccines. 1 While there is a preference that doses in a series come from the same manufacturer when feasible, vaccination should never be deferred when the manufacturer of the previously administered vaccine is unknown or when the vaccine from the same manufacturer is unavailable. 1

Practical Implementation

When to Interchange Brands

• If you don't know which brand was previously administered, use any available varicella-containing vaccine to continue or complete the series 1
• If the previously used brand is unavailable, proceed with the available product without delay 1
• Available data demonstrate that infants receiving sequential doses of different vaccine brands produce satisfactory antibody responses after completing the primary series 1

Age-Specific Considerations

For children 12 months through 12 years:

• Either monovalent varicella vaccine (Varivax) or combination MMRV vaccine (ProQuad) can be used interchangeably 1, 2
• The minimum interval between doses is 3 months (though doses given as early as 28 days apart don't need repeating) 2

For persons 13 years and older:

• Only single-antigen varicella vaccine (Varivax) should be used, as MMRV is not licensed for this age group 2
• The minimum interval between doses is 4 weeks 2

Key Differences Between Products

While interchangeable, there are compositional differences worth noting:

• Varivax (monovalent): Contains minimum 1,350 PFU (approximately 3.13 log10 PFU) of Oka/Merck VZV per 0.5 mL dose 1
• ProQuad (MMRV): Contains higher varicella antigen concentration with minimum 3.99 log10 PFU per dose 1

Despite these potency differences, both products achieve comparable immunogenicity and protection when used in the two-dose series. 1

Clinical Outcomes with Interchangeability

The two-dose varicella vaccination schedule provides:

• 98% efficacy against any varicella disease (compared to 94% with one dose) 2
• Recipients of two doses are 3.3-fold less likely to experience breakthrough varicella 2, 3

• 99% of children achieve protective antibody levels after two doses 2

These outcomes are maintained regardless of whether the same brand is used for both doses. 1

Common Pitfalls to Avoid

• Don't delay vaccination waiting to identify or obtain the previously used brand 1
• Don't restart the series if switching brands mid-series—simply continue where you left off 1
• Don't accept self-reported vaccination history without written documentation, but if restarting, any brand is acceptable 1
• Don't use MMRV (ProQuad) for persons ≥13 years—it's only licensed for ages 12 months through 12 years 2