The Effect of Monovalent Influenza Vaccine on the Risk of Hospitalization and All-Cause Mortality According to the Results of Randomized Clinical Trials: A Systematic Review and Meta-Analysis

Background: In recent years, various studies have been conducted to investigate the role of the influenza vaccine in reducing the risk of hospitalization and mortality; however, the results of these studies are clearly contradictory. Accordingly, we aimed to investigate the effect of monovalent flu vaccines on the risk of hospitalization and all -cause mortality.Methods: This study was a systematic review and meta-analysis of Randomized Clinical Trial (RCT) studies published in databases (Web of Science (ISI), Scopus, PubMed, Cochrane, Science Direct, Google Scholar) from 1980 to Dec 2022. All analyzes were performed by Stata15 statistical software and the significance level in this study was considered 0.05.Results: In the initial search, 375 articles were retrieved which, considering the study criteria, finally 8 RCT were included in the meta-analysis of the effects of monovalent Flu vaccine on the risk of hospitalization, and 10 RCT on the risk of all-cause mortality. Based on the results of meta-analysis, the overall Odds Ratio (OR) of hospital-ization is equal to 0.71 (95% CI: 0.56-0.90; P <0.001) and the overall OR of all-cause mortality is equal to 0.82 (95% CI: 0.68-0.98; P=0.033). There was no publication bias in the study of the effect of monovalent flu vaccine on the risk of hospitalization and all-cause mortalityConclusion: Getting the flu vaccine can reduce the risk of hospitalization by 29% and the risk of overall death by 18%. Therefore, it may be promising to receive this vaccine as a preventive intervention for deaths and hos-pitalizations.