Safety of a refrigerator-stable varicella vaccine (VARIVAX) in healthy 12- to 15-month-old children: A randomized, double-blind, cross-over study

Abstract

The safety of a single injection of the refrigerator-stable formulation of varicella vaccine VARIVAX was assessed in a blind, randomized, cross-over trial. Five hundred seven healthy children aged 12 to 15 months received subcutaneous injections of VARIVAX on day 0 and the measles, mumps and rubella vaccine (M-M-R II) on day 42 or M-M-R II on day 0 and VARIVAX on day 42. To maintain blinding, injections were given by a study nurse not involved in safety assessments. M-M-R II acted as a reference to validate the safety assessment, as its safety profile is well known in this age range. Parents or legal guardians recorded adverse events for 42 days following each injection. Solicited injection-site reactions (erythema, swelling, pain) were recorded on days 0 to 4. Other injection-site reactions, daily temperature, rashes and systemic adverse events were recorded on days 0 to 42, and serious adverse events until the final study visit. The safety profile of M-M-R II was consistent with previous reports. Following VARIVAX administration, 47.7% of children had at least one vaccine-related adverse event. Solicited injection-site reactions were reported in 13.0% of children, and 17.2% had at least one other injection-site reaction between days 0 and 42. Most reactions were small (<or=2.5 cm) or of mild intensity. Pyrexia, reported in 25.3% of children, was the most common vaccine-related systemic adverse event. Varicella or varicella-like rashes were reported in 16 children (3.2%), of which seven cases were varicella-like rashes at the injection site. In summary, the refrigerator-stable formulation of VARIVAX had a good safety profile and was well tolerated in healthy children aged 12 to 15 months, consistent with experience with the frozen formulation of VARIVAX.

Trial registration: ClinicalTrials.gov NCT00432731.