Seasonal influenza vaccine exposure in pregnancy: 5-year results from a pregnancy registry.

The World Health Organization recommends that all pregnant women receive seasonal influenza vaccine. Under a post-authorization safety study protocol (NCT02148211), a pregnancy exposure registry was established in the United States to monitor spontaneously reported pregnancy outcomes in women vaccinated with GSK's seasonal inactivated influenza vaccines (IIVs). From 1 June 2014 to 31 May 2019, 507 pregnancies were prospectively reported: 352 (69.4%) were lost to follow-up and 40 (7.9%) were ongoing. Reported outcomes for the remaining 115 were: 101 (87.8%) live births without congenital anomalies; 3 (2.6%) live births with congenital anomalies; 2 (1.7%) spontaneous abortions with no congenital anomalies; 1 (0.9%) spontaneous abortion with a congenital anomaly; 1 stillbirth with no apparent congenital anomaly; 7 (6.1%) 'Unknown'. Results from 493 prospective reports received via worldwide spontaneous, passive surveillance showed similar outcomes. All cases with congenital anomaly were assessed as not likely/unlikely/unrelated to vaccination. Despite the limited number of cases and outcomes, no safety signal was identified. The study findings are aligned with previously published data and should be confirmed with other robust data sources.