Exposure to quadrivalent influenza vaccine during pregnancy: Results from a global pregnancy registry

Background: The Fluzone® Quadrivalent (IIV4, Sanofi Pasteur) Pregnancy Registry was created to monitor vaccine safety during pregnancy (clinicaltrials.gov, NCT01945424). Here, we describe maternal, pregnancy, obstetrical and neonatal outcomes after vaccine exposure in pregnant women between August 2013 and September 2019.

Methods: All women exposed to IIV4 during their pregnancy were eligible for inclusion. Outcomes were prospective (reported following vaccine exposure but before knowledge of pregnancy outcome ascertained through prenatal tests) or retrospective (prenatal tests were undertaken before the exposure was reported).

Results: Among 239 IIV4 vaccine exposure reports received, there were 105 prospective and 10 retrospective reports of maternal adverse events (AEs). The most frequent prospectively reported maternal AEs were medication errors (expired product [n = 8, 3.8%]; extra dose [n = 7, 3.3%]) and injection site pain (n = 7, 3.3%). Among 62 prospectively reported pregnancy and obstetrical events with available follow-up information, seven AEs were reported, four (6.4%) of which were spontaneous abortions. A further seven AEs were reported among the 29 retrospective pregnancy and obstetrical events with available follow-up information. Among neonatal outcomes (15 prospective; 28 retrospective), >85% were reported as full-term births. One premature birth was reported prospectively. Four other neonatal AEs were reported, all retrospectively: two cases of talipes (club foot), one central nervous system anomaly and one atrial septal defect. All infants with available information had normal APGAR scores at 5 minutes.

Conclusions: The frequency of AEs following exposure to IIV4 during pregnancy did not indicate new safety concerns.