Safety of RSV Vaccine among Pregnant Individuals: A Real-World Pharmacovigilance Study Using Vaccine Adverse Event Reporting System

Abstract

Objectives:To describe the post-marketing safety of RSVPreF among pregnant individuals.Design:This case series study analyzed adverse event (AE) reports submitted to the U.S. Food and Drug Administration's Vaccine Adverse Event Reporting System (VAERS) database following RSVPreF immunization from September 1, 2023, to February 23, 2024.Setting:VAERS, as a national spontaneous vaccine safety surveillance system, provides insights into the safety profile of the RSVPreF vaccine in a real—world setting.Participants:Surveillance data included all AE reports submitted to VAERS for pregnant individuals following vaccination.Exposure:Receipt of RSVPreF vaccine among pregnant individuals in the U.S.Primary and secondary outcome measures:Descriptive statistics assessed all AE reports with RSVPreF, including frequency, gestational age at vaccination, time to AE onset, and serious report proportions. The Bayesian Confidence Propagation Neural Network (BCPNN) was utilized, estimating the information component (IC) to identify disproportionate reporting of RSVPreF—event pairs.Results:VAERS received 77 reports pertained to RSVPreF vaccination in pregnant individuals, with 42 (54.55%) classified as serious. The most reported non-pregnancy-specific AEs were headache, injection site erythema, and injection site pain. Preterm birth was the most frequently reported pregnancy-specific AE, followed by preterm premature rupture of membranes, cesarean section, cervical dilatation, and hemorrhage during pregnancy. The median time from immunization to reported preterm birth was 3 days, with two-thirds of cases within a week. Disproportionality analysis indicated a significant signal for various AEs, particularly highlighting preterm birth with an IC of 2.18 (95%CI, 1.54–2.63), suggesting that reports of preterm birth associated with RSVPreF vaccination occurred more frequently than statistically expected.Conclusions:While reported AEs were generally consistent with the safety profile observed in prelicensure studies, this study highlights ongoing concern about preterm birth among pregnant individuals following RSVPreF vaccination. Comprehensive longitudinal follow-up, including prospective pregnancy registries and infant follow-up studies is urgently required.