Varicella Vaccine Exposure During Pregnancy: Data From 10 Years of the Pregnancy Registry

Abstract

Varivax (Merck), or varicella virus vaccine, is a live, attenuated viral vaccine intended to prevent varicella disease. Its use is contraindicated in pregnant women, and current recommendations are that pregnancy be avoided for 1 to 3 months after vaccination. Nevertheless, some women have inadvertently been vaccinated while pregnant. The investigators reviewed information in the Pregnancy Registry for Varivax, which was established to monitor the offspring of pregnant women exposed to varicella vaccine. The registry receives voluntary reports from health care providers or consumers about women given the vaccine 3 months before or during pregnancy. A total of 981 women were enrolled in the Registry in the years 1995–2005. Pregnancy outcomes were available for 629 prospectively enrolled women. No evidence of congenital varicella syndrome was obtained in 131 live births to varicella-zoster virus (VZV)-seronegative women. Three infants (3.7%) had major birth defects (95% confidence interval, 0.8%–10.7%). Approximately two-thirds of VZV-seronegative women in this study were vaccinated during the first or second trimester—thought to be a high-risk period. All 18 live-born infants whose mothers inadvertently received varicella vaccine rather than VZV immunoglobulin were reportedly healthy and without birth defects. Eight of these infants were born to VZV-seronegative mothers. The number of exposures analyzed is not great enough to rule out a very low risk, but they fail to support a relationship between exposure to varicella vaccine during pregnancy and either congenital varicella syndrome or other birth defects. Even so, women of reproductive age who are vaccinated should be advised to avoid becoming pregnant for 1–3 months afterward.