Chorioamnionitis following vaccination in the Vaccine Adverse Event Reporting System

In October 2012, the Advisory Committee on Immunization Practices (ACIP) recommended a dose of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) during each pregnancy, irrespective of the woman's prior history of receiving Tdap. A retrospective cohort study to assess the safety of Tdap vaccination in pregnant women in two Vaccine Safety Datalink (VSD) sites during 2010-2012 found a small but statistically significant increased risk of chorioamnionitis.

We conducted a review of the VAERS database to describe reports of chorioamnionitis following receipt of any vaccines.

We searched the VAERS database for reports of chorioamnionitis after any vaccine in the United States during the period from July 1, 1990 through February 2, 2014.

VAERS received 31 reports of chorioamnionitis out of 3389 pregnancy reports in 24 years. The three most common vaccines in these reports were 2009 H1N1 inactivated influenza, quadrivalent human papillomavirus (HPV4), and Tdap vaccines in 32%, 29% and 26% of reports, respectively. Fifty-eight percent of reports had at least one reported risk factor for chorioamnionitis. Chorioamnionitis was identified in 3 reports of spontaneous abortions and 6 stillbirths, 6 reports of preterm birth (two of whom died) and 16 reports of term birth; maternal outcomes included two reports of postpartum hemorrhage and one report of maternal admission to the intensive care unit. No maternal deaths were reported.

Chorioamnionitis was found to be uncommonly reported, representing 1% of pregnancy reports to VAERS. A majority of reports had at least one risk factor for chorioamnionitis.