International Journal of Molecular Medical Science, 2025, Vol.15, No.4, 165-174 http://medscipublisher.com/index.php/ijmms 165 Research Insight Open Access Clinical and Immunological Factors Affecting Vaccine Efficacy in Frail Older Adults Hua Xu, Manman Li Hainan Institute of Biotechnology, Haikou, 570206, Hainan, China Corresponding author: manman.li@hibio.org International Journal of Molecular Medical Science, 2025, Vol.15, No.4 doi: 10.5376/ijmms.2025.15.0017 Received: 19 May, 2025 Accepted: 09 Jul., 2025 Published: 20 Jul., 2025 Copyright © 2025 Xu and Li, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Xu H., and Li M., 2025, Clinical and immunological factors affecting vaccine efficacy in frail older adults, International Journal of Molecular Medical Science, 15(4): 165-174 (doi: 10.5376/ijmms.2025.15.0017) Abstract This study explores the physical and immune reasons why elderly people with weak constitutions and frequent illnesses have poor responses after vaccination. Physical weakness is a common health problem encountered by the elderly. It interacts with the aging of the immune system, jointly weakening the body's humoral and cellular immune responses to vaccines. This leads to a smaller increase in antibodies, a slower response, and a shorter protection period after vaccination. Physical reasons include whether the nutrition is good or not, whether the metabolism is normal or not, whether there is a long-term illness, whether multiple medications are taken at the same time, and the lifestyle and daily activity ability, etc. All of these will alter the efficacy of vaccines by influencing the function of the immune system. From the perspective of the immune system, the main issue is the decline in T cell capacity, the weakening of antibodies produced by B cells, and the combined effect of long-term mild inflammation in the body and some factors that suppress the immune system. This article also explores methods to enhance the efficacy of vaccines, such as improving the vaccine formula and booster shots, conducting immunomodulatory treatment, and adjusting the timing of injections and the arrangement of booster shots. In the future, accurate immunization tests, large-scale trials conducted in collaboration with multiple hospitals, research on the immune system and overall analysis methods should be carried out to predict and improve vaccine responses and promote personalized vaccination plans. Keywords Frailty; Immunosenescence; Vaccine efficacy; Inflammaging; Personalized vaccination 1 Introduction Nowadays, there are more and more elderly people in the world, and the proportion of people aged 65 and above in the total population is getting larger and larger. This demographic change has brought about significant public health problems, as the elderly are more prone to infectious diseases such as influenza, pneumonia, shingles and COVID-19. Compared with young people, they are at a higher risk of getting sick, dying and leaving long-term disabilities. The physical changes brought about by aging, having other diseases and deteriorating body functions can make infections more severe. Therefore, formulating effective preventive measures, especially vaccination, is the key to making the elderly healthier and reducing their medical burden (Wagner and Weinberger, 2020; Cadar et al., 2023; Incalzi et al., 2023). Frailty is a common condition among the elderly, characterized by a decline in physical reserve capacity and greater sensitivity to stress, such as infections. It is different from simply getting older, which means poorer health outcomes, greater chances of hospitalization and a higher risk of death. In terms of immunity, physical weakness is increasingly regarded as a key factor influencing immune function It often aggravates "immunosenescence"-the phenomenon where the body's first line of defense (innate immunity) and specific defense (adaptive immunity) capabilities decline with age (Cadar et al., 2023). Elderly people with weak constitutions usually produce fewer antibodies after vaccination, and the response of immune cells also weakens, leading to a decline in the protective effect of the vaccine and an increased risk of infection and complications (Ridda et al., 2009; Semelka et al., 2023). Physical weakness, long-term illness and immune system problems interact with each other, forming a cycle of "susceptibility to illness", which poses a challenge to traditional vaccination strategies (Yao et al., 2011; Wagner and Weinberger, 2020; Incalzi et al., 2023).
RkJQdWJsaXNoZXIy MjQ4ODYzNA==