Pharmacoepidemiologic implications of erroneous varicella vaccinations in pregnancy through confusion with Varicella zoster immune globulin.

A series of case reports to the varicella vaccine Pregnancy Registry described inadvertent administrations during pregnancy of this live virus product instead of the intended Varicella zoster immune globulin. Cases continued to accrue despite an early publication about the pattern. The persistent problem warrants specific educational efforts to prevent further repetitions. It also has more general implications for medical product safety surveillance. First, this problem's original detection depended on the Pregnancy Registry's open-ended collection of information about pregnancy exposures. It could have escaped recognition through surveillance limited to pre specified potential risks. This need for unrestricted reporting and human vigilance to sift through case stories has particular relevance for efforts to re-think methods to monitor gestational drug exposures. In addition, the problem's persistence despite initial publicity suggests that diligent surveillance may require continued follow-up of identified safety issues. Periodic reassessments of selected preventable problems might strengthen efforts to minimize product risks.