"1. Introduction
... There are numerous reports of adverse events following COVID-19 vaccination, with particular emphasis on specific groups such as the elderly, pregnant women. and those with pre-existing medical conditions. Furthermore, retrospective reports have highlighted vaccine-related neurological adverse events and cardiovascular complications. These reports significantly impact public willingness to receive vaccinations, consequently affecting vaccination rates. Of particular concern are the severe adverse events associated with booster vaccines, such as vaccine-induced myocarditis and pericarditis, multisystem inflammatory syndrome in children (MIS-C), and multisystem inflammatory syndrome in adults (MIS-A). The question of whether the incidence and severity of side effects increase with additional doses is of utmost importance and urgently requires detailed clinical reports to understand the current situation...
The risk of AEs could be repeated upon subsequent administrations of the same vaccine. Given the variety of COVID-19 vaccines available, each based on different technological platforms such as mRNA and non-replicating viral vectors, potential mechanisms for this could involve immunological responses such as hypersensitivity or immune sensitization, especially relevant in the context of repeated exposures to vaccine antigens. Moreover, the risk of AEs could be cumulative, potentially due to cumulative immunological effects or other underlying biological factors. This cumulative aspect is paramount in assessing the long-term safety and sustainability of ongoing COVID-19 vaccination strategies, particularly in the context of administering booster doses. A comprehensive analysis of these mechanisms, in terms of pharmacovigilance, is vital for enhancing the efficacy and safety of current and future vaccination strategies against COVID-19 and other diseases.
... This research utilizes data from the Vaccine Adverse Event Reporting System (VAERS) at Taipei Veterans General Hospital to analyze the types and incidence rates of AEs, and the correlation between the occurrence of AEs after the first and second boosters. Additionally, we evaluate whether the occurrence of AEs is a repeated phenomenon or indicative of a cumulative risk of AEs. Furthermore, we explore the relationship between the choice of vaccine brand and the booster–booster combination in relation to the occurrence of AEs...
3. Results
Over a three-month period, Taipei Veterans General Hospital administered COVID-19 vaccinations to 1711 individuals. From this group, 452 reported their post-vaccination outcomes to VAERS between 27 October 2022 and 19 January 2023. A total of 441 respondents were ultimately included in this analysis...
4. Discussion
... The incidence rates of adverse events (AEs) were relatively high, at 25.6% after the first booster and 24.9% after the second. Most notably, these AEs were predominantly non-serious, with symptoms such as injection site pain and fatigue being the most common. We observed the pattern of adverse events (AEs) following COVID-19 booster vaccinations to be repetitive rather than cumulative, where individuals who experienced an AE following the first booster were more likely to report AEs after the second booster. This finding underscores the importance of considering previous AEs, the brand of the second booster, and the booster combination in devising personalized vaccination strategies...
In our study, we observed a considerable incidence rate of adverse events (AEs) post COVID-19 booster vaccinations... The finding is compatible with a recent systematic review of 22 randomized controlled trials involving over 3.4 million older adults reporting an overall incidence rate of adverse events at 36.6%."
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