[Connection between viral infections, vaccines, and dementia]

Dementia represents a growing public health challenge in the elderly population worldwide, with its development being influenced by multifactorial mechanisms. In recent years, increasing evidence has supported the notion that certain viral infections – particularly herpesviruses, the human immunodeficiency virus (HIV), and SARS-CoV-2 – may contribute to neurodegenerative processes either directly or indirectly. It has been demonstrated that chronic inflammation, immune system dysregulation, and blood–brain barrier damage induced by viral agents potentially promote the pathogenesis of dementia, especially Alzheimer’s disease. Simultaneously, remarkable new research has emerged highlighting the potential protective effects of vaccination. According to a study conducted by Stanford University and published in 2025, elderly adults vaccinated against herpes zoster (shingles) exhibited a significantly lower incidence of dementia over a 7-year follow-up period. Researchers identified a 20% relative risk reduction, particularly among women. Other studies have supported similar effects for vaccines against influenza, tetanus, and diphtheria. The aim of our publication was to summarize the causative role of viral infections in dementia and to present the inhibitory effects of vaccines, which likely extend beyond specific antiviral infection prevention. Furthermore, we sought to emphasize the clinical and public health significance of these findings, particularly for the elderly population with compromised immune systems. Orv Hetil. 2025; 166(45): 1763–1768.