(1134) Safety and Efficacy of Influenza Vaccination in Pregnancy: Umbrella review and meta-analyses

Friday, January 31, 2025

4:00 PM – 6:00 PM

Submitting Author and Presenting Author(s)

Nikan Zargarzadeh, MD

Research Fellow
Boston Children's Hospital, Harvard Medical School
Boston, Massachusetts, United States

Coauthor(s)

Giulia Bonanni, MD

Postdoctoral Research Fellow
Postdoctoral Research Fellow Fetal Care and Surgery Center Division of Fetal Medicine and Surgery Boston Children's Hospital, Harvard Medical School
Boston, MA, United States
MH

Mohammad Haddadi, MD

Vali-E-Asr Reproductive Health Research Center, Family Health Research Institute, Tehran University of Medical Sciences, Tehran, Iran
Tehran, Tehran, Iran
Ali Javinani, MD (he/him/his)

Postdoctoral Research Fellow
Boston Children's Hospital, Harvard Medical School
Boston, Massachusetts, United States
James Versalovic, MD, PhD

Pathology-in-Chief
Department of Pathology & Immunology, Baylor College of Medicine, Houston, TX, USA Department of Pathology, Texas Children’s Hospital
Houston, Texas, United States
Kjersti M. Aagaard, MD, PhD

Medical Director, HCA Healthcare and HCA Research Institute
Boston Children’s Hospital, Division of Fetal Medicine and Surgery, Boston, MA; HCA Healthcare and HCA Healthcare Research Institute, Nashville, TN; HCA Texas Maternal Fetal Medicine, Houston, TX; Baylor College of Medicine and Texas Children's Hospital, Houston, TX
Tomball, Texas, United States
SP

Stefania Papatheodorou, MD, MSc, PhD

Department of Epidemiology, Harvard T.H. Chan School of Public Health, Harvard University, Boston, MA, USA Department of Biostatistics and Epidemiology, Rutgers School of Public Health, New Brunswick, NJ, USA
New Brunswick, New Jersey, United States
Alireza A. Shamshirsaz, MD (he/him/his)

Department Director, Professor of Surgery
Fetal Surgeon Chief, Division of Fetal Medicine and Surgery Director of the Maternal Fetal Care Center Director of the Perinatal Surgery Fellowship Professor of Surgery, Boston Children’s Hospital Harvard Medical School
Boston, Massachusetts, United States

Objective: Although influenza vaccination during pregnancy is known to prevent seasonal flu outbreaks, reliable and contemporary quantitation of benefits and safety has not been performed. The aim of the current umbrella review to synthesize evidence from multiple meta-analyses was to reliably and robustly provide quantitative measures of the effectiveness and safety of influenza vaccines among gravidae.

Study Design:

We conducted a systematic search of PubMed, Scopus, Web of Science, and Embase from inception to 09/13/2023, including over 100 individual studies retaining 38 million pregnancies. Data were extracted from multiple meta-analyses, and included studies were filtered to ensure no duplication within outcomes. Risk ratios (RRs) and pooled proportions were calculated using R, with aggregate effect sizes and random-effects models applied. Egger’s test was used to assess publication bias. PROSPERO registration: CRD42024519189.

Results:

As shown in Figure & Table, influenza vaccination during pregnancy resulted in a significant risk reduction of fetal death or stillbirth (RR 0.83 & 0.77, 95% CI 0.78–0.89 and 0.69–0.87), PTB (RR 0.92, 95% CI 0.88–0.96), and LBW neonates (RR 0.88, 95% CI 0.84-0.93). Reflective of changes in co-morbidities and other respiratory illness pandemics over the study interval, there was heterogeneity in some outcomes, such as PTB (I²: 63.06%), while other outcomes showed low to moderate heterogeneity. Egger’s test for publication bias indicated no significant bias across the studies.

Conclusion:

Influenza vaccination during pregnancy is associated with significant and quantifiable reductions in the risk ratio of multiple adverse perinatal outcomes. Providing these quantitative estimates may aid in public health messaging and shared decision-making with patients and their families.