International Journal of Molecular Medical Science, 2025, Vol.15, No.4, 165-174 http://medscipublisher.com/index.php/ijmms 166 This study will explore how clinical factors and the state of the immune system (immune factors) affect the vaccine efficacy of physically weak elderly people. By studying the effects of physical faltering, "immune system aging", and related physical and disease factors, this review aims to identify any gaps in our knowledge and provide useful strategic information for improving the vaccine response of this vulnerable population. Understanding these factors is of great significance for designing targeted vaccination methods, improving health outcomes, and guiding future research and policies targeting the global aging population. 2 Physical Weakness and an Aging Immune System 2.1 What is physical weakness, how to diagnose it and how common it is Physical weakness is a common and complex condition among the elderly, mainly manifested as reduced strength, easy fatigue and poor physical functions. This makes it more difficult for the body to resist stress like infection and also reduces the body's response to treatment. It is different from simple aging, which makes the elderly more prone to disability, hospitalization and even death. One of the common methods for judging physical frailty is the "Fried Frailty Criterion", which mainly examines whether there is unexpected weight loss, frequent fatigue, reduced grip strength, slower walking and less physical activity. Another commonly used tool is the "frailties Index", which calculates how many health problems a person has (Moehling et al., 2020). In terms of the incidence rate, the older one gets, the more likely their body is to become weak. This situation is very common among people over 65 years old. Studies have found that a weakened body accelerates the aging of the immune system, making the body less responsive to infections and vaccines. Although physical weakness is often closely related to aging, not all elderly people will experience this. Scientists are still studying its impact on people's ability to produce antibodies after vaccination. Some studies have found that in frail elderly people, the activity of some genes that control the growth of immune cells, energy use and antiviral signaling has changed, and the response of immune cells has also slowed down (Moehling et al., 2020). 2.2 The main manifestations of immune system aging Immune system aging refers to the weakening and alteration of the immune system as one ages, which affects the body's first line of defense (innate immunity) and the defense line specifically against certain pathogens (adaptive immunity). On the first line of defense, aging leads to a decline in the ability of neutrophils, monocytes, dendritic cells and natural killer cells, resulting in their poor ability to recognize pathogens, consume pathogens and signal. The characteristic of the specialized defense part is that the number of T cells and B cells capable of recognizing new bacteria decreases, while the number of T cells that remember old bacteria and are aging increases. The antibodies produced by the body and the attack ability of T cells both weaken, making it more difficult for the body to deal with new bacteria (Crooke et al., 2019; Oh et al., 2019; Pereira et al., 2020; Aiello et al., 2022). A clear sign of an aging immune system is that the body remains in a mild state of inflammation for a long time, which is called "inflammation". This persistent mild inflammation is due to the body producing more substances that promote inflammation. It is associated with poor vaccination efficacy and a higher risk of infection (Oh et al., 2019; Pereira et al., 2020; Aiello et al., 2022). These changes in the immune system interact with the aging physical environment, making the immune condition of the elderly more complex. 2.3 Physical weakness and an aging immune system jointly reduce the efficacy of vaccines Physical weakness and an aging immune system can interact with each other, jointly reducing the protective effect of vaccines on the elderly. Physical weakness will accelerate the aging of the immune system, making both humoral immunity (antibodies) and cellular immunity (direct attack by immune cells) weaker. Research shows that in physically weak elderly people, the activities of some genes that control immune cell division, energy metabolism and interferon signaling pathways have changed. At the same time, T cells are more prone to "fatigue", and the number of oxidative stress markers in the body has also increased. These changes may not be detectable by simple antibody level tests. These changes have led to a slower, weaker response to vaccines or a shorter protection period for them, making them more susceptible to infection (Moehling et al., 2020; Pereira et al., 2020).
RkJQdWJsaXNoZXIy MjQ4ODYzNA==