Real-World Incidence of Adverse Events Following COVID-19 Vaccination: Systematic Review and Meta-Analysis – Supplementary Materials

This repository contains supplementary materials related to the systematic review and meta-analysis titled “Real-World Incidence of Adverse Events Following COVID-19 Vaccination.” The study aimed to estimate and synthesize real-world incidence measures of adverse events following immunization (AEFI) associated with COVID-19 vaccines and to examine how methodological and epidemiological factors influence reported incidence estimates. In accordance with PRISMA 2020 guidelines and prior PROSPERO registration, eight data sources, including grey literature, were systematically searched to identify observational studies reporting AEFI incidence in the general population. A total of 160 studies met the inclusion criteria. Incidence metrics varied by unit of analysis and included events per notification, events per exposed individual, events per 100 administered doses, and cumulative incidence of individuals experiencing at least one AEFI. Random-effects meta-analyses were conducted in R. Pooled estimates differed according to the mathematical structure of the incidence metric. Event-based incidence rates yielded a combined estimate of 0.118 with a 95% confidence interval of 0.066 to 0.211, whereas cumulative incidence proportions produced a pooled estimate of 0.561 with a 95% confidence interval of 0.336 to 0.763. Statistical heterogeneity was substantial, with I² values of 99 percent or higher. Subgroup analyses demonstrated variation across age groups, vaccine platforms, number of doses, data sources, and study designs. Most included studies were rated as having moderate to high risk of bias. The materials provided in this repository are intended to ensure transparency, reproducibility, and methodological traceability of the review process and statistical analyses.