Safety and Varicella Outcomes in In Utero–Exposed Newborns and Preterm Infants Treated With Varicella Zoster Immune Globulin (VARIZIG): A Subgroup Analysis of an Expanded-Access Program

Background Infants exposed to varicella zoster virus (VZV) in utero ≤5 days before or ≤48 hours after delivery and preterm infants are at high risk for varicella complications. An expanded-access program assessed varicella outcomes after administration of varicella zoster immune globulin (human) (VARIZIG) in a real-world setting. Methods In this open-label, expanded-access program, high-risk infants received ≤125 IU/10 kg of VARIZIG (NCT00338442). VZV outcomes and safety were assessed. Results There were 43 newborns exposed to VZV in utero and 80 preterm infants exposed to VZV; >80% received VARIZIG within 96 hours of reported exposure. When varicella outcomes were available, varicella occurred in 7 of 38 (18%) in utero–exposed newborns and zero of 65 preterm infants. Varicella-related complications were reported in 3 in utero–exposed newborns (3 with >100 lesions, 1 each with encephalitis and pneumonia). Adverse events were reported for 16% of in utero–exposed newborns and 25% of preterm infants, but few were considered related to VARIZIG. There were no deaths attributable to varicella or VARIZIG. Conclusions Varicella incidence and morbidity were low in in utero–exposed infants and zero in preterm infants who received prophylactic VARIZIG. There were few VARIZIG-related safety concerns.