Coronavirus disease 2019 (COVID-19) vaccines played a major role in reducing severe illness, hospitalization, and mortality worldwide. Booster doses were introduced to maintain immunity against emerging variants and waning antibody responses. Although booster vaccination has shown significant public health benefits, post-vaccination complications and adverse events have been increasingly reported. Most adverse effects are mild and self-limiting, including fever, fatigue, headache, and injection-site pain. However, rare but serious complications such as myocarditis, thrombosis, Guillain–Barré syndrome, autoimmune reactions, and neurological manifestations have also been documented. This review summarizes the currently available evidence regarding complications associated with COVID-19 booster vaccination, mechanisms involved, clinical manifestations, diagnosis, management, and preventive strategies. The review also discusses vaccine safety surveillance systems and the balance between vaccine benefits and risks.
1*A. Sneha, 2S. Ahammad, 2D. C. Gowri Thrinay, 1Dr. E. Sunil Kumar (2026) studied this question.