Effectiveness of oral aciclovir in preventing maternal chickenpox: A comparison with VZIG

Objectives Although often presenting as a self-limiting childhood disease, chickenpox can have serious consequences if acquired in pregnancy. The UK recommendations are that varicella immunoglobulin (VZIG) is administered intramuscularly to susceptible pregnant women exposed to chickenpox prior to 20 weeks gestation. Oral aciclovir or VZIG is recommended if exposure occurs at 20+ weeks gestation. Our objective was to compare the effectiveness of oral aciclovir to VZIG in preventing maternal and neonatal chickenpox. Methods We identified and followed up 186 pregnant women who were exposed to chickenpox and compared their outcomes. Results 171/186 (91.9%) of these women received either VZIG or oral aciclovir. 53 of the 145 (36.6%) women who received VZIG went on to develop chickenpox compared to 8 of the 26 (30.8%) women who received oral aciclovir (p=0.32). No statistical difference was found between the oral aciclovir and VZIG groups even after controlling for maternal age, gestational stage, type of exposure and IgG titre (adjusted OR:0.83; 95%CI:0.26-2.65; p=0.751). Conclusions These findings support the use of oral aciclovir as first-line prophylaxis in pregnant women exposed at 20+ weeks, (and possibly second-line <20 weeks) as they suggest its effectiveness at preventing maternal chickenpox is either better or equal to VZIG.