Adverse Effects of M-RNA Vaccine on Health After COVID-19 in COVID-19 mRNA Vaccine Takers Worldwide

Esomchukwu Enoch Okpara

Abstract: The rapid development and global adoption of messenger ribonucleic acid (mRNA) vaccines against Coronavirus Disease 2019 (COVID-19) represented a major advancement in modern medicine and public health. Despite the demonstrated effectiveness of these vaccines in reducing severe illness, hospitalization, and mortality, concerns regarding their potential adverse effects on human health have remained a subject of scientific investigation and public debate. This study aimed to analyse the adverse health effects associated with mRNA COVID-19 vaccines using a systematic literature review and meta-analysis of available scientific studies. A comprehensive search of electronic databases including PubMed, Scopus, Embase, Web of Science, Cochrane Library, and Google Scholar was conducted using vital keywords related to mRNA vaccines and adverse events. Additional data were gotten from pharmacovigilance systems such as the Vaccine Adverse Event Reporting System (VAERS), the Centers for Disease Control and Prevention (CDC), and the World Health Organization (WHO). Studies published between 2020 and 2026 that investigated adverse effects associated with Pfizer-BioNTech and Moderna mRNA vaccines were added. Data extraction and quality checks were performed using standardized methodological tools, while pooled estimates were analyzed using random-effects meta-analysis models. The findings showed that the majority of adverse effects associated with mRNA vaccines were mild and transient, including injection-site pain, fatigue, fever, headache, and myalgia. Serious adverse effects were rare but included myocarditis, pericarditis, neurological complications, thrombotic events, and allergic reactions. Myocarditis and pericarditis were the most commonly reported significant adverse effects, particularly among young males after the second vaccine dose. However, the absolute incidence remained low, and most cases resolved with conservative treatment. Neurological and thrombotic complications were uncommon, while anaphylactic reactions rarely occurred and were generally manageable with prompt medical intervention. Importantly, no substantial evidence was identified which indicated that mRNA vaccines alter human DNA, cause infertility, or produce widespread long-term systemic disease. The study further demonstrated that the risks associated with COVID-19 infection itself, including severe cardiovascular and respiratory complications, significantly exceeded the risks associated with vaccination. Overall, the evidence supports the conclusion that mRNA COVID-19 vaccines has a favorable safety profile and that their public health benefits outweigh the associated risks in most populations. Continued long-term surveillance, transparent reporting, and evidence-based communication remain important for optimizing vaccine safety and maintaining public confidence.

Keywords: mRNA COVID-19 vaccines, vaccine safety, adverse health effects, myocarditis, pharmacovigilance

How to Cite?: Esomchukwu Enoch Okpara, "Adverse Effects of M-RNA Vaccine on Health After COVID-19 in COVID-19 mRNA Vaccine Takers Worldwide", Volume 15 Issue 9, September 2026, International Journal of Science and Research (IJSR), Pages: 802-807, https://www.ijsr.net/getabstract.php?paperid=SR26911061003, DOI: https://dx.doi.org/10.21275/SR26911061003

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