Association between seasonal influenza vaccination and neonatal outcomes in Shanghai, China

While international and domestic recommendations advocating for influenza vaccination during pregnancy, the vaccination rate among this demographic in China remains low, mainly due to concerns about fetal safety. This retrospective cohort enrolled mothers who registered and delivered between August 2020 and July 2023. The relationship between maternal influenza vaccination and adverse neonatal outcomes was assessed using Poisson regression models and logistic regression analyses. The adverse neonatal outcomes under evaluation included small for gestational age (SGA), large for gestational age (LGA), preterm birth (PTB), low birth weight (LBW), low Apgar score, congenital anomalies, neonatal intensive care unit (NICU) admission or referral, as well as stillbirth or neonatal death. Of the 2,517 women, 203 (8.1%) had received influenza vaccination during their pregnancies. The incidence rate of gestational complications in the vaccinated group being significantly higher than that in the unvaccinated group. In comparison with no vaccination, there was no statistically connection between vaccination and an increased risk of any adverse neonatal outcomes. The adjusted risk ratios (95% CIs) were: SGA 1.354 (0.842-2.177), LGA 1.504 (0.808-2.798), PTB 0.639 (0.257-1.590), LBW 0.294 (0.072-1.211), low Apgar score 0.918 (0.213-3.958), congenital anomaly 0.676 (0.087-5.247), and NICU admission or referral 0.151 (0.021-1.089). In this study, there was only 1 stillbirth and 1 neonatal death in the unvaccinated group, resulting in a cumulative incidence of 0.1%. No stillbirths or neonatal deaths occurred in the vaccinated group. These findings endorse public health initiatives aimed at enhancing vaccination rates among pregnant women.