A double-blind, randomized, controlled, multi-center safety and immunogenicity study of a refrigerator-stable formulation of VARIVAX®.

Objective: VARIVAX® (varicella virus vaccine, live Oka/Merck, Merck & Co., Inc., Kenilworth, NJ, USA) was originally licensed as a frozen formulation. A refrigerator-stable formulation of VARIVAX was subsequently developed to allow for increased availability of the product around the world. The objective of this study (V210-051) was to demonstrate that the safety, tolerability and immunogenicity profile of the refrigerator-stable formulation of VARIVAX was similar to the frozen formulation.

Methods: In this double-blind, randomized, multicenter study, healthy 12- to 23-month-old children with negative vaccination and clinical histories for measles, mumps, rubella, varicella, and zoster were vaccinated with either a refrigerator-stable formulation of VARIVAX (at two dosage levels; 8000 PFU [N = 320] or 25,000 PFU [N = 315]) or the frozen formulation of VARIVAX (10,000 PFU, N = 323) given concomitantly with M-M-RII® (measles, mumps, and rubella virus vaccine live, Merck & Co., Inc., Kenilworth, NJ, USA). Children were followed for 42 days after vaccination for adverse experiences. Immunogenicity was evaluated 6 weeks after vaccination.

Results: The refrigerator-stable formulation of VARIVAX was generally well tolerated. The incidence of adverse experiences was similar between all three groups. No vaccine-related serious adverse experiences were reported with any of the vaccine formulations. The immune response (percentage of subjects with varicella antibody titers ≥5 gpELISA units) for both refrigerator-stable formulations of VARIVAX at 6 weeks postvaccination was similar to that of the frozen formulation. Administration of either refrigerator-stable formulation of VARIVAX with M-M-RII yielded seroconversion rates and GMTs for measles, mumps and rubella that were comparable to those achieved after administration of the frozen formulation of VARIVAX with M-M-RII.

Conclusion: The safety, tolerability, and immunogenicity profile of the refrigerator-stable varicella vaccine was similar to that of the frozen formulation.