Effect of zoster immunoglobulin for varicella prophylaxis in the newborn.

Zoster immunoglobulin (ZIG) was given for prophylaxis to 95 neonates born to mothers with perinatal varicella. The treatment had no influence on the clinical attack rate; 48 (50%) of the children developed varicella. However, the ZIG treatment clearly influenced the course of the disease for newborns at particular risk, i.e. when maternal varicella developed within 4 days before and 2 days after delivery. Of 41 such neonates, 21 (51%) contracted varicella with an incubation mean time of 11 days. 13 of the 21 developed a very mild chickenpox (no fever, less than or equal to 20 pocks), 6 had a mild to normal disease, and 2 (10%) had more severe infections; none died or got sequelae after the disease. These results should be compared with the expected rate of complications in non-treated neonates in the defined risk group, where the mortality among those contracting varicella has been reported to be as high as about 30%.