Abstract
BACKGROUND AND AIMS: Population aging is a significant demographic change while vaccines are mostly made for children and young adults and their effectiveness might be low in the older population. Age-associated decline in the immune function (immunosenescence) is a process that may lead to poor vaccine response in the older population. This comprehensive review aims to discuss changes in the immune system with age and their impact on vaccine response to develop strategies to enhance vaccine efficacy in the elderly. METHODS: This literature review on how the immune system changes with age and affects vaccine responses in older adults was carried out by examining English-language publications. The search involved relevant keywords such as "Antibody response," "Vaccine Efficacy," "Vaccine Response," "Immune Aging," "Immunosenescence," "Inflammaging," and "Older Adults" across multiple databases, including Google Scholar, PubMed, Scopus, and Web of Science. RESULTS: Age-related changes in the immune system, such as structural changes in lymphatic tissues, a decrease in the number of naive cells, an increase in the number of dysfunctional memory cells, along with a change in the microbiota profile and its contribution to inflammaging and an increase in the number of senescent cells are factors that lead to vaccine effectiveness decreases with age. CONCLUSION: A deeper understanding of age-related alterations and their effect on vaccine efficacy can provide new insights into the enhancement of vaccine-induced immunity in the older population.