Influenza: The Disease Burden, Clinical Spectrum, Risk Groups, and the Role of Vaccination in Immunocompromised Patients

Background: Influenza is a very common communicable viral infection affecting the respiratory tract that contributes significantly to global morbidity, mortality, and periodic pandemics. People with diabetes mellitus (DM) are particularly vulnerable due to impaired immune responses and poor glycemic control during infection. Annual influenza vaccination remains the most effective preventive measure and is strongly recommended for all individuals aged 6 months and older. Objective: This study aimed to summarize current evidence on influenza epidemiology, disease burden, affected organ systems, high-risk groups, vaccine recommendations, and the specific benefits of influenza vaccination for diabetic individuals. Methodology: A narrative review approach was followed, synthesizing evidence from global health guidelines, peer-reviewed literature, and World Health Organization/Centers for Disease Control and Prevention recommendations. Types of influenza viruses, systemic impacts, vaccine categories, high-risk populations, dosing schedules, and the importance of vaccination for individuals with DM. A structured search by the electronic databases, including PubMed/MEDLINE. Data were collected from January 2000 to June 2025. Results: Findings indicate that influenza A and B viruses are primarily responsible for seasonal epidemics and severe complications. High-risk groups, including children, older adults, pregnant women, those with chronic conditions, and healthcare workers, experience disproportionately high hospitalization and mortality rates. Annual influenza vaccination significantly reduces infection, complications, and healthcare burden. For diabetic individuals, vaccination markedly lowers influenza-related hospital admissions, cardiovascular events, mortality, and risks of poor glycemic control. Conclusion: Influenza remains a major global health threat because of its transmissibility and potential for severe systemic complications. Vaccination is the most effective strategy for preventing disease, protecting vulnerable groups, and reducing healthcare strain.