Adverse Events of COVID-19 Vaccines in the United States: Temporal and Spatial Analysis

Abstract

Background: COVID-19, a highly contagious respiratory disease, has rapidly emerged as a global pandemic. By 3 March 2024, 103.4 million confirmed cases of COVID-19 had been reported in the United States. Vaccination against COVID-19 is currently considered one of the most effective strategies to control its spread. However, due to variations in populations and the ongoing development of vaccines, it is expected that a certain number of individuals may experience adverse events following immunization (AEFI) for COVID-19 vaccines.Objective: In this study, we exclusively examined AEFI associated with COVID-19 vaccination reported by vaccine recipients. Our objective was to analyze the temporal and spatial characteristics of these reported AEFI to gain insights into their patterns and distribution. Methods:We analyzed the administration data from the Centers for Disease Control and Prevention (CDC) (N = 663,822,575) and the reports from the surveillance system-Vaccine Adverse Event Reporting System (VAERS) (N = 900,522) between 2020 and 2022. To gain a broader understanding of reported post-vaccination AEFI, we categorized them into System Organ Classes (SOCs) according to the Medical Dictionary for Regulatory Activities (MedDRA). Additionally, temporal analysis was conducted to examine the trends of AEFI in all VAERS reports, those related to Pfizer and Moderna as well as the Top 10 AEFI trends in serious reports. We also compared the similarity of symptoms across various regions within the United States.Results: Our findings revealed that the most frequently reported symptoms following COVID-19 vaccination were headache (N = 141,186), pyrexia (N = 122,120), and fatigue (N = 121,910). The most common symptom combination was chills and pyrexia (N = 56,954). Initially, General disorders and administration site conditions (SOC 22) were the most prevalent class reported. Moderna exhibited a higher reporting rate of AEFI compared to Pfizer. Over time, we observed a decreasing reporting rate for COVID-19-related AEFI. And the overall rates of AEFI between the Pfizer and Moderna vaccines were comparable. In terms of spatial analysis, the middle and north regions displayed a higher reporting rate of AEFI for COVID-19 vaccines, while the southeast and south central regions showed notable similarity in reported COVID-19 symptoms. Conclusions:This study presents a potentially beneficial method for AEFI surveillance, especially for severe cases, which can intensify research efforts in areas where abnormal or severe presentations occur. The findings suggest that increasing vaccination coverage reduces the reported AEFI, thereby enhancing vaccine confidence. Our study highlights the importance of robust health policies for managing AEFI in future vaccination campaigns. Specifically, health authorities should consider implementing targeted monitoring programs to detect and manage AEFI early, especially for symptoms that were severe and frequently reported in our analysis. These programs can help improve public confidence in COVID-...