Efficacy and Safety of Vaccinations in Geriatric Patients: A Literature Review

Vaccinations in older adults: Optimization, strategies, and latest guidelines

This article is a summary of the first AGS Symposium entitled "Update on Vaccination Strategies for Older Adults: Matching the Approach to the Individual and the Care Setting." Given declines in host defenses and immune function with aging, vaccinations play a pivotal role in fortifying older adults against preventable infections, resulting diseases, disability, and death. Current guidelines generally list recommendations applicable for an average older adult of a given chronological age. However, growing evidence indicates that heterogeneity in terms of factors as varied as biological sex, frailty, functional status, and multimorbidity may impact vaccine responses and clinical outcomes. As a result, clinicians will increasingly need to take these additional factors into consideration as they seek to improve outcomes through improved targeting of such aging-related heterogeneity. Moreover, efforts at protecting older citizens through vaccination must also include strategies to overcome barriers to the adoption of vaccine recommendations in varied settings including long-term care. This 2023 AGS Plenary Symposium sought to commence a broader dialogue across AGS and beyond on optimizing vaccinations for older adults, ensuring not only extended lifespans but also healthier and more active lives. This report is not a systematic review, and thus should not be considered comprehensive.

The desire of autonomy: A lever for vaccination of the elderly? Results of a qualitative study

The COVID-19 pandemic has highlighted the challenges of vaccination and the infectious risks among the elderlies. However, immunization rates for recommended vaccines in this population are insufficient in France. We aimed in this study to identify the levers and obstacles to vaccination among seniors, and to establish the arguments that could lead to some new vaccination behaviors. A qualitative survey based on 14 semi-structured interviews was conducted with people aged 65 and over, living at home in the Auvergne Rhône-Alpes region (France) from March to May 2022. The interviews were recorded, entirely transcribed, then subjected to a thematic content analysis. The results show that participants are keen to preserve their health by maintaining their physical capacity, taking regular exercise and eating a balanced diet. However, vaccination was not mentioned as a mean of preventing infectious diseases. Infections were not perceived as a cause for concern. Furthermore, the physical and cognitive consequences of infectious diseases, which could result in a loss of autonomy, were not known. These elements could be a good lever to bring hesitant elderly people to reconsider their position toward vaccination. Vaccines were not seen as a strategy to prevent loss of autonomy among elderlies. Since vaccines against influenza, COVID-19, shingles, pneumococcus have proved to be effective in protecting against cardiovascular events, this argument might be the starting point for a prevention campaign for the elderly.

Enhancing vaccine effectiveness in the elderly to counter antibiotic resistance: The potential of adjuvants via pattern recognition receptors

Vaccines are an effective way to prevent the emergence and spread of antibiotic resistance by preventing diseases and establishing herd immunity. However, the reduced effectiveness of vaccines in the elderly due to immunosenescence is one of the significant contributors to the increasing antibiotic resistance. To counteract this decline and enhance vaccine effectiveness in the elderly, adjuvants play a pivotal role. Adjuvants are designed to augment the effectiveness of vaccines by activating the innate immune system, particularly through pattern recognition receptors on antigen-presenting cells. To improve vaccine effectiveness in the elderly using adjuvants, it is imperative to select the appropriate adjuvants based on an understanding of immunosenescence and the mechanisms of adjuvant functions. This review demonstrates the phenomenon of immunosenescence and explores various types of adjuvants, including their mechanisms and their potential in improving vaccine effectiveness for the elderly, thereby contributing to developing more effective vaccines for this vulnerable demographic.

Infectious Disease as a Modifiable Risk Factor for Dementia: A Narrative Review

This narrative review examines infectious diseases as modifiable risk factors for dementia, particularly in the context of an aging global population. As the prevalence of Alzheimer's disease and related dementias is expected to rise, prevention has become increasingly important due to the limited efficacy of current treatments. Emerging evidence links specific infectious diseases to increased dementia risk, possibly through mechanisms like neuroinflammation and disruption to normal cell function. Here, we review findings on how viral and bacterial infections contribute to dementia and explore potentially preventive measures, including vaccinations and antiviral treatments. Studies indicate that vaccinations against influenza, herpes zoster, and hepatitis, as well as antiviral treatments targeting human herpesvirus, could reduce the incidence of dementia. Additionally, non-pharmaceutical interventions during pandemics and in long-term care settings are highlighted as effective strategies for reducing the spread of infectious diseases, potentially lowering dementia risk. Putative mechanisms underlying the protective effects of these interventions suggest that reducing systemic inflammation may be important to their efficacy. While the currently available evidence suggests at best an association between some infectious diseases and dementia, this narrative review emphasizes the need to incorporate infectious disease prevention into broader public health strategies to potentially mitigate the growing burden of dementia. Further research is required to explore these preventive measures across diverse populations and to deepen our understanding of the biological mechanisms involved.

Aging amplifies a gut microbiota immunogenic signature linked to heightened inflammation

Aging is associated with low-grade inflammation that increases the risk of infection and disease, yet the underlying mechanisms remain unclear. Gut microbiota composition shifts with age, harboring microbes with varied immunogenic capacities. We hypothesized the gut microbiota acts as an active driver of low-grade inflammation during aging. Microbiome patterns in aged mice strongly associated with signs of bacterial-induced barrier disruption and immune infiltration, including marked increased levels of circulating lipopolysaccharide (LPS)-binding protein (LBP) and colonic calprotectin. Ex vivo immunogenicity assays revealed that both colonic contents and mucosa of aged mice harbored increased capacity to activate toll-like receptor 4 (TLR4) whereas TLR5 signaling was unchanged. We found patterns of elevated innate inflammatory signaling (colonic Il6, Tnf, and Tlr4) and endotoxemia (circulating LBP) in young germ-free mice after 4 weeks of colonization with intestinal contents from aged mice compared with young counterparts, thus providing a direct link between aging-induced shifts in microbiota immunogenicity and host inflammation. Additionally, we discovered that the gut microbiota of aged mice exhibited unique responses to a broad-spectrum antibiotic challenge (Abx), with sustained elevation in Escherichia (Proteobacteria) and altered TLR5 immunogenicity 7 days post-Abx cessation. Together, these data indicate that old age results in a gut microbiota that differentially acts on TLR signaling pathways of the innate immune system. We found that these age-associated microbiota immunogenic signatures are less resilient to challenge and strongly linked to host inflammatory status. Gut microbiota immunogenic signatures should be thus considered as critical factors in mediating chronic inflammatory diseases disproportionally impacting older populations.

Impact of ageing on homologous and human-coronavirus-reactive antibodies after SARS-CoV-2 vaccination or infection

The endemic human coronaviruses (HCoVs) circulate worldwide yet remain understudied and unmitigated. The observation of elevated levels of HCoV reactive antibodies in COVID-19 patients highlights the urgent necessity of better understanding of HCoV specific immunity. Here, we characterized in-depth the de novo SARS-CoV-2 specific antibody responses and the boosting of HCoV-reactive antibodies after SARS-CoV-2 vaccination or infection in individuals up to 98 years old. All the vaccinees were home-dwelling with no documented SARS-CoV-2 infection before receiving the COVID-19 mRNA vaccine (BNT162b2). The first two vaccine doses elicited potent SARS-CoV-2 spike binding antibodies in individuals up to 80 years. The third dose largely boosted the previously low S2 domain binding and neutralizing antibodies in elderly 80-90 years old, but less so in those above 90 years. The endemic betacoronavirus (HKU1 and OC43) reactive antibodies were boosted in all vaccinees, although to a lesser extent in those above 80 years old. COVID-19 patients had potent elevation of alpha- and betacoronavirus (229E, NL63, HKU1 and OC43) reactive antibodies. In both patients and vaccinees, S2 domain specific antibody increases correlated with SARS-CoV-2 neutralizing and HCoV-reactive antibody responses in all ages, indicating S2 domain as a candidate for future universal coronavirus vaccine design.