The Importance of Frailty in the Assessment of Influenza Vaccine Effectiveness Against Influenza-Related Hospitalization in Elderly People

Enhanced influenza vaccination for older adults in Europe: a review of the current situation and expert recommendations for the future

INTRODUCTION

Influenza causes considerable morbidity and mortality in Europe, particularly among older adults due to comorbidities, as well as immunosenescence and inflammaging, which contribute to a diminished immune response. Vaccination remains the most effective way to prevent poor outcomes; however, uptake is suboptimal and many countries recommend standard vaccines despite evidence supporting better protection with enhanced (adjuvanted and high-dose) vaccines.

AREAS COVERED

A multidisciplinary group of experts reviewed the burden of influenza in Europe and evaluated data on enhanced vaccines, providing recommendations for their use in older adults. The group discussed barriers to vaccination and strategies to increase uptake.

EXPERT OPINION

Improving protection of older adults against influenza relies upon increasing vaccine uptake and ensuring access to vaccines that overcome age-related immunological decline. Achieving higher uptake requires national policies that facilitate equitable access and clear communication about vaccine eligibility. Based on available evidence, enhanced vaccines offer better protection than standard vaccines against hospitalization and complications in older adults. National recommendations should prioritize the use of enhanced influenza vaccines over standard vaccines in older adults. Limitations to interpretation of evidence include discrepancies in reporting of influenza-related medical encounters and underreporting of influenza-related complications.

Uptake of Influenza Vaccine among Older Adults with Cardiovascular Comorbidities

BACKGROUND

Influenza vaccination reduces illness and fatality in older adults, especially those with cardiovascular comorbidities.

OBJECTIVE

To investigate influenza vaccination uptake among community-dwelling older Brazilian patients with cardiovascular comorbidities.

METHODS

This cross-sectional study analyzed data from the ELSI-Brazil Second wave (2019-2021), involving 9,949 older adults. Participants with cardiovascular conditions provided data on influenza vaccination from the previous year. Vaccination-associated factors were identified, with subgroup analyses for each cardiovascular comorbidity. An exploratory analysis investigated the primary reasons for non-vaccination. Statistical significance was determined with a two-sided P-value < 0.05.

RESULTS

This study included 5,296 individuals. Of these, 76.6% reported receiving the influenza vaccine within the year before data collection. Vaccinated individuals were generally older females, widowed, and non-smokers with healthier habits and private healthcare access, although they had higher frailty and cardiovascular comorbidities. Age significantly influenced the likelihood of vaccination across subgroups. In hypertension, private healthcare and good health status increased the odds, while smoking and alcohol consumption reduced them. The most common reasons for not receiving the influenza vaccine were fear of adverse reactions (18.2%), belief in a low-risk infection (14.9%), vaccine unavailability (13.9%), and lack of confidence in its effectiveness (12%).

CONCLUSION

About 24% of older Brazilian adults with cardiovascular conditions remain unvaccinated against influenza, posing severe health risks. Strategies addressing personal beliefs, improving access, and enhancing healthcare provider engagement are crucial. Tailored interventions should align with the population's demographic and health characteristics to overcome these barriers effectively.

Oseltamivir Reduces 30-Day Mortality in Older Adults With Influenza: A Pooled Analysis From the 2012-2019 Serious Outcomes Surveillance Network of the Canadian Immunization Research Network

Background

Oseltamivir is recommended for the treatment of adults hospitalized with influenza, but adherence is often suboptimal. This may be due to doubts about the reliability of the evidence supporting its benefits, particularly when initiation is delayed. We aimed to assess the effectiveness of oseltamivir in reducing mortality in older adults hospitalized with influenza, with a focus on the timing of initiation.

Methods

The CIRN-SOS Network gathered data on severe respiratory illnesses across 5 Canadian provinces during the influenza seasons 2012-2019. Individuals aged ≥65 years with confirmed influenza and available antiviral prescription data were included. We compared the 30-day survival rates of hospitalized patients based on oseltamivir prescription status. Kaplan-Meier estimated survival probability and inverse probability of treatment (IPT)-weighted Cox proportional hazard models were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for mortality. The analyses considered the time to antiviral initiation (>48 vs ≤48 hours).

Results

Among the 8135 influenza patients studied, 2126 did not receive antiviral treatment, whereas 6009 were treated with oseltamivir. A total of 395 patients were hospitalized for >30 days. The overall mortality rate was 8.32 per 1000 person-days, with 53.9% of the deaths occurring within the first week. Oseltamivir recipients had a 18% lower risk of 30-day mortality (IPT-weighted HR, 0.82 [95% CI, .69-.98]). The benefit was significant for influenza A (IPT-weighted HR, 0.74 [95% CI, .61-.91]) but not for influenza B (IPT-weighted HR, 1.12 [95% CI, .81-1.56]). Oseltamivir remained effective even when initiated after 48 hours (IPT-weighted HR, 0.66 [95% CI, .49-.90]). Influenza vaccination did not mediate the effectiveness of oseltamivir in reducing mortality.

Conclusions

Oseltamivir significantly reduces mortality risk in older adults hospitalized with influenza, even when administered after 48 hours, independent of vaccination status. Clinical Trials Registration. NCT01517191.

COVID-19 vaccine safety and effectiveness at 3 months in institutionalized old people

BACKGROUND

Older age and associated comorbid conditions increase the risk of severe form of COVID-19 and death. The SARS-CoV-2 vaccination campaign began in France in December 2020 targeting institutionalized older population before having been evaluated in this population. The objective of our study was to assess the tolerability of vaccination 21 days (D21) and 90 days after the first vaccination (D90) in institutionalized old people. Secondary objective was to assess its effectiveness (mortality, hospitalization and occurrence of COVID) at D21 and D90.

METHODS

People living in nursing homes or in long-term hospitalization facilities in France were included 12-2020-06-2021. They were divided into SARS-CoV-2 vaccinated and unvaccinated groups. Vaccine tolerability was prospectively assessed by the occurrence of health events at D21 and D90 (local and systemic side effects, geriatric syndromes, cardiovascular events). Vaccine efficacy was assessed by the occurrence of COVID-19 and serious adverse events (unscheduled hospitalization and all-cause mortality).

RESULTS

The mean age of the 2595 participants was 86 years, 83% received COVID-19 vaccine. There were no significant difference between the vaccinated and unvaccinated for systemic or local adverse events at D21 and D90. At D90, vaccinated participants had significantly fewer SARS-CoV-2 infections (odds ratio (95% confidence interval) = 0.35 (0.22-0.58)), fewer deaths or hospitalizations (0.50 (0.31-0.81)), fewer cardiovascular events (0.28 (0.12-0.64)) and fewer pressure ulcers (0.38 (0.17-0.88)).

CONCLUSIONS

In this prospective cohort study, COVID-19 vaccine in a very old institutionalized geriatric population had a reassuring safety profile and a protective effect on COVID-19, hospitalizations and deaths, cardiovascular events and pressure ulcers.

A standard procedure for constructing a multi-level social vulnerability index using CLSA and SOS data as working examples

BACKGROUND

The construct of social vulnerability attempts to understand social circumstances not merely as a descriptor, but as a predictor of adverse health events. It can be measured by aggregating social deficits in a social vulnerability index (SVI). We describe a standard procedure for constructing a multi-level SVI using two working examples.

METHODS

First, we describe a six-step approach to constructing a SVI. Then, we conducted a secondary analysis of a clinical dataset (Canadian Immunization Research Network's Serious Outcomes Surveillance Network (SOS)) and a population-based dataset (Canadian Longitudinal Study on Aging (CLSA)). In both datasets, we construct SVIs, use descriptive statistics to report distributions by age and sex, and perform a multivariable linear regression of social vulnerability on frailty.

RESULTS

Procedures for drafting a list of candidate social items, selecting deficits for inclusion, and screening deficits to meet inclusion criteria were applied to yield a 18-deficit SVI for the SOS and 74-deficit SVI for the CLSA. Deficits in each SVI were re-scored between 0 and 1, where 1 indicates the greater risk. Finally, the sum of all deficits is calculated into an index. In the SOS, SVI was associated with age only for females and was weakly associated with frailty (r = 0.26, p<0.001). In the CLSA, SVI was associated with age for both sexes and moderately associated with frailty (r = 0.41, p<0.001).

CONCLUSION

We present a standard method of constructing a SVI by incorporating factors from multiple social domains and levels in a social-ecological model. This SVI can be used to improve our understanding of social vulnerability and its impacts on the health of communities and individuals.

Measuring the impact of influenza vaccination in the Netherlands using retrospective observational primary care, hospitalisation and mortality data

We aimed to estimate the impact of influenza vaccination in the Netherlands using general practitioner medical records for 2011-2020. We found that vaccinees had higher consultation rates for influenza-like-illness, acute respiratory infections, and pneumonia, as well as antibiotic use, hospitalisations, and several control diagnoses (i.e. illnesses for which there was no a priori expectation that influenza vaccination would play a protective effect). We found similar rates for respiratory mortality and lower all-cause mortality in the vaccinees versus non-vaccinees, mainly driven by the 75+ age group. These results expand, but are fairly consistent with those of previous investigations, and highlight the difficulty of using registry data to assess the impact of vaccination, because of underlying differences between vaccinees and non-vaccinees. Whether these biases also play a role for hospitalisations and mortality remains unclear. Our findings support the implementation of randomized studies to assess the impact of influenza vaccination.

Assessing the Impact of Frailty on Infection Risk in Older Adults: Prospective Observational Cohort Study

Background

Infectious diseases are among the leading causes of death and disability and are recognized as a major cause of health loss globally. At the same time, frailty as a geriatric syndrome is a rapidly growing major public health problem. However, few studies have investigated the incidence and risk of infectious diseases in frail older people. Thus, research on frailty and infectious diseases is urgently needed.

Objective

The purpose of this study was to evaluate the association between frailty and infectious diseases among older adults aged 65 years and older.

Methods

In this prospective observational cohort study, we have analyzed the infectious disease prevalence outcomes of older adults aged 65 years and older who participated in frailty epidemiological surveys from March 1, 2018, to March 2023 in Dalang Town, Dongguan City, and from March 1, 2020, to March 2023 in Guancheng Street, Dongguan City. This study has an annual on-site follow-up. Incidence data for infectious diseases were collected through the Chinese Disease Control and Prevention Information System-Infectious Disease Monitoring and Public Health Emergency Monitoring System. A project-developed frailty assessment scale was used to assess the frailty status of study participants. We compared the incidence rate ratios (IRR) of each disease across frailty status, age, and gender to determine the associations among frailty, gender, age, and infectious diseases. Cox proportional hazards regression was conducted to identify the effect of frailty on the risk of demographic factors and frailty on the risk of infectious diseases, with estimations of the hazard ratio and 95% CI.

Results

A total of 235 cases of 12 infectious diseases were reported during the study period, with an incidence of 906.21/100,000 person-years in the frailty group. In the same age group, the risk of infection was higher in men than women. Frail older adults had a hazard ratio for infectious diseases of 1.50 (95% CI 1.14-1.97) compared with healthy older adults. We obtained the same result after sensitivity analyses. For respiratory tract-transmitted diseases (IRR 1.97, 95% CI 1.44-2.71) and gastrointestinal tract-transmitted diseases (IRR 3.67, 95% CI 1.39-10.74), frail older adults are at risk. Whereas no significant association was found for blood-borne, sexually transmitted, and contact-transmitted diseases (IRR 0.76, 95% CI 0.37-1.45).

Conclusions

Our study provides additional evidence that frailty components are significantly associated with infectious diseases. Health care professionals must pay more attention to frailty in infectious disease prevention and control.

Predicting major clinical events among Canadian adults with laboratory-confirmed influenza infection using the influenza severity scale

We developed and validated the Influenza Severity Scale (ISS), a standardized risk assessment for influenza, to estimate and predict the probability of major clinical events in patients with laboratory-confirmed infection. Data from the Canadian Immunization Research Network's Serious Outcomes Surveillance Network (2011/2012-2018/2019 influenza seasons) enabled the selecting of all laboratory-confirmed influenza patients. A machine learning-based approach then identified variables, generated weighted scores, and evaluated model performance. This study included 12,954 patients with laboratory-confirmed influenza infections. The optimal scale encompassed ten variables: demographic (age and sex), health history (smoking status, chronic pulmonary disease, diabetes mellitus, and influenza vaccination status), clinical presentation (cough, sputum production, and shortness of breath), and function (need for regular support for activities of daily living). As a continuous variable, the scale had an AU-ROC of 0.73 (95% CI, 0.71-0.74). Aggregated scores classified participants into three risk categories: low (ISS < 30; 79.9% sensitivity, 51% specificity), moderate (ISS ≥ 30 but < 50; 54.5% sensitivity, 55.9% specificity), and high (ISS ≥ 50; 51.4% sensitivity, 80.5% specificity). ISS demonstrated a solid ability to identify patients with hospitalized laboratory-confirmed influenza at increased risk for Major Clinical Events, potentially impacting clinical practice and research.

Immunogenicity of BNT162b2 as a first booster after a ChAdOx1 primary series in a Thai geriatric population living with frailty

OBJECTIVES

Impact of frailty towards immunogenicity and reactogenicity of BNT162b2 boosters administered via intramuscular or intradermal routes in a Thai geriatric population DESIGN: Prospective, randomized, open-labeled.

SETTING

Siriraj Hospital, Thailand.

PARTICIPANTS

Geriatric adults aged ≥65 years.

INTERVENTION

10 μg intradermal or 30 μg intramuscular BNT162b2 (Pfizer-BioNTech).

MEASUREMENTS

Anti-SARS-CoV-2 receptor binding domain IgG, neutralizing antibodies (NAb), and interferon-gamma producing cells against Wuhan and Omicron BA.4/5. Analyses were stratified based on participants' Clinical Frailty Scale.

RESULTS

A total of 139 participants were included in the analysis. Two-four weeks post-booster administration, NAb titers against Wuhan but not Omicron BA.4/5 were significantly lower among frail participants than non-frail participants who received intramuscular administration. Spike-specific T cell responses were similar for frail and non-frail participants, regardless of administration route. Frail participants who received intradermal BNT162b2 had fewer local adverse events (AEs), but higher systemic AEs than non-frail participants.

CONCLUSION

Similar immune responses across vaccine routes warrants further evaluation of intradermal BNT162b2 in frail geriatric populations. Frail participants may be more sensitive to reporting systemic AEs.

REGISTRATION OF CLINICAL TRIALS

The parent study was registered under the Thai Clinical Trials Registry (TCTR20220112002).

Immunotherapy use in older adults with cancer with frailty: A young SIOG review paper

Immune checkpoint inhibitors (ICIs) became a treatment option in most tumor types and improved survival in patients with cancer in the last decade. Older patients with cancer are underrepresented in the pivotal clinical trials with ICIs. Older patients with cancer often have significant comorbidities and geriatric syndromes like frailty, which can complicate cancer care and treatment decisions. Frailty is among the most prevalent geriatric syndromes in patients with cancer and could lead to inferior survival and a higher risk of complications in patients treated with chemotherapy. However, the effect of frailty on the efficacy and safety of ICIs is understudied. This review focuses on the available evidence regarding the association between frailty and ICI efficacy and safety. Although the survival benefits of ICIs have generally been shown to be independent of age, the available real-world data has generally suggested higher rates of immune-related adverse events (irAEs) and treatment discontinuation in older patients. While international organizations recommend conducting a comprehensive geriatric assessment CGA to assess and address frailty before the start of anti-cancer therapies, an Eastern Cooperative Oncology Group (ECOG) performance status of 2 or higher is frequently used in clinical practice as synonymous with frailty, albeit with significant limitations. The available data has generally demonstrated diminished ICI efficacy in patients with an ECOG 2 or higher compared to patients with better performance status, while the incidence of high-grade irAEs were similar. Whilst evidence regarding outcomes with ICI in older patients and in those with sub-optimal performance status is growing, there is very limited data specifically evaluating the role of frailty with ICIs. These studies found a shortened overall survival, yet no evidence of a lower response rate to ICIs. These patients experienced more AEs, but they did not necessarily have a higher incidence of irAEs.

Insights into vaccines for elderly individuals: from the impacts of immunosenescence to delivery strategies

Immunosenescence increases the risk and severity of diseases in elderly individuals and leads to impaired vaccine-induced immunity. With aging of the global population and the emerging risk of epidemics, developing adjuvants and vaccines for elderly individuals to improve their immune protection is pivotal for healthy aging worldwide. Deepening our understanding of the role of immunosenescence in vaccine efficacy could accelerate research focused on optimizing vaccine delivery for elderly individuals. In this review, we analyzed the characteristics of immunosenescence at the cellular and molecular levels. Strategies to improve vaccination potency in elderly individuals are summarized, including increasing the antigen dose, preparing multivalent antigen vaccines, adding appropriate adjuvants, inhibiting chronic inflammation, and inhibiting immunosenescence. We hope that this review can provide a review of new findings with regards to the impacts of immunosenescence on vaccine-mediated protection and inspire the development of individualized vaccines for elderly individuals.

Influenza vaccination for elderly, vulnerable and high-risk subjects: a narrative review and expert opinion

Influenza is associated with a substantial health burden, especially in high-risk subjects such as older adults, frail individuals and those with underlying chronic diseases. In this review, we summarized clinical findings regarding the impact of influenza in vulnerable populations, highlighted the benefits of influenza vaccination in preventing severe illness and complications and reviewed the main evidence on the efficacy, effectiveness and safety of the vaccines that are best suited to older adults among those available in Italy. The adverse outcomes associated with influenza infection in elderly and frail subjects and those with underlying chronic diseases are well documented in the literature, as are the benefits of vaccination (mostly in older adults and in patients with cardiovascular diseases, diabetes and chronic lung disease). High-dose and adjuvanted inactivated influenza vaccines were specifically developed to provide enhanced immune responses in older adults, who generally have low responses mainly due to immunosenescence, comorbidities and frailty. These vaccines have been evaluated in clinical studies and systematic reviews by international immunization advisory boards, including the European Centre for Disease Prevention and Control. The high-dose vaccine is the only licensed influenza vaccine to have demonstrated greater efficacy versus a standard-dose vaccine in preventing laboratory-confirmed influenza in a randomized controlled trial. Despite global recommendations, the vaccination coverage in high-risk populations is still suboptimal. All healthcare professionals (including specialists) have an important role in increasing vaccination rates.

Clinical features and outcomes of influenza and RSV coinfections: a report from Canadian immunization research network serious outcomes surveillance network

BACKGROUND

Influenza and RSV coinfections are not commonly seen but are concerning as they can lead to serious illness and adverse clinical outcomes among vulnerable populations. Here we describe the clinical features and outcomes of influenza and RSV coinfections in hospitalized adults.

METHODS

A cohort study was performed with pooled active surveillance in hospitalized adults ≥ 50 years from the Serious Outcomes Surveillance Network of the Canadian Immunization Research Network (CIRN SOS) during the 2012/13, 2013/14, and 2014/15 influenza seasons. Descriptive statistics summarized the characteristics of influenza/RSV coinfections. Kaplan-Meier estimated the probability of survival over the first 30 days of hospitalization.

RESULTS

Over three influenza seasons, we identified 33 cases of RSV and influenza coinfection, accounting for 2.39 cases per 1,000 hospitalizations of patients with acute respiratory illnesses. Adults aged 50 + years commonly reported cough (81.8%), shortness of breath (66.7%), sputum production (45.5%), weakness (33.3%), fever (27.3%), and nasal congestion (24.2%) as constitutional and lower respiratory tract infection symptoms. The mortality rate was substantial (12.1%), and age, comorbidity burden, and frailty were associated with a higher risk for adverse clinical outcomes.

CONCLUSIONS

Older adults are at higher risk for complications from influenza and RSV coinfections, especially those over 65 with a high comorbidity burden and frailty.

To Be Frail or Not to Be Frail: This Is the Question-A Critical Narrative Review of Frailty

Many factors have contributed to rendering frailty an emerging, relevant, and very popular concept. First, many pandemics that have affected humanity in history, including COVID-19, most recently, have had more severe effects on frail people compared to non-frail ones. Second, the increase in human life expectancy observed in many developed countries, including Italy has led to a rise in the percentage of the older population that is more likely to be frail, which is why frailty is much a more common concern among geriatricians compared to other the various health-care professionals. Third, the stratification of people according to the occurrence and the degree of frailty allows healthcare decision makers to adequately plan for the allocation of available human professional and economic resources. Since frailty is considered to be fully preventable, there are relevant consequences in terms of potential benefits both in terms of the clinical outcome and healthcare costs. Frailty is becoming a popular, pervasive, and almost omnipresent concept in many different contexts, including clinical medicine, physical health, lifestyle behavior, mental health, health policy, and socio-economic planning sciences. The emergence of the new "science of frailty" has been recently acknowledged. However, there is still debate on the exact definition of frailty, the pathogenic mechanisms involved, the most appropriate method to assess frailty, and consequently, who should be considered frail. This narrative review aims to analyze frailty from many different aspects and points of view, with a special focus on the proposed pathogenic mechanisms, the various factors that have been considered in the assessment of frailty, and the emerging role of biomarkers in the early recognition of frailty, particularly on the role of mitochondria. According to the extensive literature on this topic, it is clear that frailty is a very complex syndrome, involving many different domains and affecting multiple physiological systems. Therefore, its management should be directed towards a comprehensive and multifaceted holistic approach and a personalized intervention strategy to slow down its progression or even to completely reverse the course of this condition.

Impact on the time elapsed since SARS-CoV-2 infection, vaccination history, and number of doses, on protection against reinfection

SARS-CoV-2 reinfections have been frequent, even among those vaccinated. The aim of this study is to know if hybrid immunity (infection + vaccination) is affected by the moment of vaccination and number of doses received. We conducted a retrospective study in 746 patients with a history of COVID-19 reinfection and recovered the dates of infection and reinfection and vaccination status (date and number of doses). To assess differences in the time to reinfection(tRI) between unvaccinated, vaccinated before 6 months, and later; and comparing one, two or three doses (incomplete, complete and booster regime) we performed the log-rank test of the cumulative incidence calculated as 1 minus the Kaplan-Meier estimator. Also, an adjusted Cox-regression was performed to evaluate the risk of reinfection in all groups. The tRI was significantly higher in those vaccinated vs. non-vaccinated (p < 0.001). However, an early incomplete regime protects similar time than not receiving a vaccine. Vaccination before 6 months after infection showed a lower tRI compared to those vaccinated later with the same regime (adj-p < 0.001). Actually, early vaccination with complete and booster regimes provided lower length of protection compared to vaccinating later with incomplete and complete regime, respectively. Vaccination with complete and booster regimes significantly increases the tRI (adj-p < 0.001). Vaccination increases the time it takes for a person to become reinfected with SARS-CoV-2. Increasing the time from infection to vaccination increases the time in which a person could be reinfected and reduces the risk of reinfection, especially in complete and booster regimes. Those results emphasize the role of vaccines and boosters during the pandemic and can guide strategies on future vaccination policy.

A clinical and economic assessment of adjuvanted trivalent versus standard egg-derived quadrivalent influenza vaccines among older adults in the United States during the 2018-19 and 2019-20 influenza seasons

BACKGROUND

Clinical evidence supports use of enhanced influenza vaccines in older adults. Few economic outcome studies have compared adjuvanted trivalent inactivated (aIIV3) and standard egg-derived quadrivalent inactivated influenza vaccines (IIV4e).

RESEARCH DESIGN AND METHODS

A retrospective cohort study was conducted leveraging deidentified US hospital data linked to claims data during the 2018-19 and 2019-20 influenza seasons. Relative vaccine effectiveness (rVE) was compared in adults aged ≥ 65 years receiving aIIV3 or IIV4e using inverse probability of treatment weighting (IPTW) and Poisson regression. An economic assessment quantified potential real-world cost savings.

RESULTS

The study included 715,807 aIIV3 and 320,991 IIV4e recipients in the 2018-19 and 844,169 aIIV3 and 306,270 IIV4e recipients in the 2019-20 influenza seasons. aIIV3 was significantly more effective than IIV4e in preventing cardiorespiratory disease (2018-19 rVE = 6.2%; and 2019-20 rVE = 6.0%) and respiratory disease (2018-19 rVE = 8.9%; and 2019-20 rVE = 10.1%). During the 2018-19 influenza season cardiorespiratory hospitalization cost savings for the aIIV3 population were $392 M, and $221 M for the 2019-20 season. Respiratory hospitalization cost savings for the aIIV3 population were $145 M and $97 M, respectively.

CONCLUSIONS

Our findings suggest that aIIV3 provides clinical and economic advantages versus IIV4e in the elderly.

Polypharmacy and Antibody Response to SARS-CoV-2 Vaccination in Residents of Long-Term Care Facilities: The GeroCovid Vax Study

BACKGROUND AND OBJECTIVE

Polypharmacy is common in older adults, particularly among those living in long-term care facilities. This condition represents a marker of clinical complexity and might directly affect the immunological response. However, there are limited data on the association of polypharmacy with vaccine immunogenicity. This study evaluated the immune response to anti-SARS-CoV-2 vaccines in older residents of long-term care facilities as a function of the number of medications used.

METHODS

In 478 long-term care facility residents participating in the GeroCovid Vax study, we assessed SARS-CoV-2 trimeric S IgG levels through chemiluminescent assays before the vaccination and after 2, 6, and 12 months. A booster dose was administered between 6- and 12-month assessments. Sociodemographic information and data on chronic diseases and medications were derived from medical records. Based on the number of daily medications, residents were classified into the no polypharmacy (zero to four medications), polypharmacy (five to nine medications), and hyperpolypharmacy (ten or more medications) groups.

RESULTS

In the sample (mean age 82.1 years, 69.2% female), 200 (41.8%) residents were taking five or fewer medications/day (no polypharmacy), 229 (47.9%) had polypharmacy, and 49 (10.3%) had hyperpolypharmacy. Using linear mixed models adjusted for potential confounders, we found that hyperpolypharmacy was associated with a steeper antibody decline after 6 months from the first vaccine dose administration (β = - 0.29, 95% confidence interval - 0.54, - 0.03, p = 0.03) than no polypharmacy, while no significant differences were observed at 12 months.

CONCLUSIONS

The humoral immune response to SARS-CoV-2 vaccination of older residents showed only slight changes as a function of the number of medications taken. Although it seemed less durable among older residents with hyperpolypharmacy, the booster dose administration equalized such a difference.

Vaccine Effectiveness of non-adjuvanted and adjuvanted trivalent inactivated influenza vaccines in the prevention of influenza-related hospitalization in older adults: A pooled analysis from the Serious Outcomes Surveillance (SOS) Network of the Canadian Immunization Research Network (CIRN)

BACKGROUND

Influenza vaccines prevent influenza-related morbidity and mortality; however, suboptimal vaccine effectiveness (VE) of non-adjuvanted trivalent inactivated influenza vaccine (naTIV) or quadrivalent formulations in older adults prompted the use of enhanced products such as adjuvanted TIV (aTIV). Here, the VE of aTIV is compared to naTIV for preventing influenza-associated hospitalization among older adults.

METHODS

A test-negative design study was used with pooled data from the 2012 to 2015 influenza seasons. An inverse probability of treatment (IPT)-weighted logistic regression estimated the Odds Ratio (OR) for laboratory-confirmed influenza-associated hospitalization. VE was calculated as (1-OR)*100% with accompanying 95% confidence intervals (CI).

RESULTS

Of 7,101 adults aged ≥ 65, 3,364 received naTIV and 526 received aTIV. The overall VE against influenza hospitalization was 45.9% (95% CI: 40.2%-51.1%) for naTIV and 53.5% (42.8%-62.3%) for aTIV. No statistically significant differences in VE were found between aTIV and naTIV by age group or influenza season, though a trend favoring aTIV over naTIV was noted. Frailty may have impacted VE in aTIV recipients compared to those receiving naTIV, according to an exploratory analysis; VE adjusted by frailty was 59.1% (49.6%-66.8%) for aTIV and 44.8% (39.1%-50.0%) for naTIV. The overall relative VE of aTIV to naTIV against laboratory-confirmed influenza hospital admission was 25% (OR 0.75; 0.61-0.92), demonstrating statistically significant benefit favoring aTIV.

CONCLUSIONS

Adjusting for frailty, aTIV showed statistically significantly better protection than naTIV against influenza-associated hospitalizations in older adults. In future studies, it is important to consider frailty as a significant confounder of VE.

Kinetics of COVID-19 mRNA primary and booster vaccine-associated neutralizing activity against SARS-CoV-2 variants of concern in long-term care facility residents: a prospective longitudinal study in Japan

BACKGROUND

Coronavirus disease 2019 (COVID-19) remains a threat to vulnerable populations such as long-term care facility (LTCF) residents, who are often older, severely frail, and have multiple comorbidities. Although associations have been investigated between COVID-19 mRNA vaccine immunogenicity, durability, and response to booster vaccination and chronological age, data on the association of clinical factors such as performance status, nutritional status, and underlying comorbidities other than chronological age are limited. Here, we evaluated the anti-spike IgG level and neutralizing activity against the wild-type virus and Delta and Omicron variants in the sera of LTCF residents, outpatients, and healthcare workers before the primary vaccination; at 8, 12, and 24 weeks after the primary vaccination; and approximately 3 months after the booster vaccination. This 48-week prospective longitudinal study was registered in the UMIN Clinical Trials Registry (Trial ID: UMIN000043558).

RESULTS

Of 114 infection-naïve participants (64 LTCF residents, 29 outpatients, and 21 healthcare workers), LTCF residents had substantially lower anti-spike IgG levels and neutralizing activity against the wild-type virus and Delta variant than outpatients and healthcare workers over 24 weeks after the primary vaccination. In LTCF residents, booster vaccination elicited neutralizing activity against the wild-type virus and Delta variant comparable to that in outpatients, whereas neutralizing activity against the Omicron variant was comparable to that in outpatients and healthcare workers. Multiple regression analyses showed that age was negatively correlated with anti-spike IgG levels and neutralizing activity against the wild-type virus and Delta variant after the primary vaccination. However, multivariate regression analysis revealed that poor performance status and hypoalbuminemia were more strongly associated with a lower humoral immune response than age, number of comorbidities, or sex after primary vaccination. Booster vaccination counteracted the negative effects of poor performance status and hypoalbuminemia on the humoral immune response.

CONCLUSIONS

LTCF residents exhibited suboptimal immune responses following primary vaccination. Although older age is significantly associated with a lower humoral immune response, poor performance status and hypoalbuminemia are more strongly associated with a lower humoral immune response after primary vaccination. Thus, booster vaccination is beneficial for older adults, especially those with a poor performance status and hypoalbuminemia.

The burden of influenza and the role of influenza vaccination in adults aged 50-64 years: A summary of available evidence

Influenza is a vaccine-preventable disease and a global public health problem. Although most national influenza vaccination recommendations focus on subjects aged ≥65 years, an extensive burden of influenza has also been reported in those aged ≥50 years and is exacerbated by immune system aging. The main purpose of this review is to provide an overview of the burden of influenza and its potential prevention within the 50-64 age-group. These subjects account for a large proportion of the workforce, and play a central economic and social role. Individuals aged 50-64 years had a 3-times higher rate of hospitalization and a 9-fold higher mortality rate attributable to influenza than those aged 18-49-years, generating higher influenza-related hospitalization costs. Available data suggest that including healthy subjects aged 50-64 years in influenza vaccination recommendations would allow a broader population to be reached, reducing the economic and social burden of influenza.

Comparative Risks of Potential Adverse Events Following COVID-19 mRNA Vaccination Among Older US Adults

Importance

Head-to-head safety comparisons of the mRNA vaccines for SARS-CoV-2 are needed for decision making; however, current evidence generalizes poorly to older adults, lacks sufficient adjustment, and inadequately captures events shortly after vaccination. Additionally, no studies to date have explored potential variation in comparative vaccine safety across subgroups with frailty or an increased risk of adverse events, information that would be useful for tailoring clinical decisions.

Objective

To compare the risk of adverse events between mRNA vaccines for COVID-19 (mRNA-1273 and BNT162b2) overall, by frailty level, and by prior history of the adverse events of interest.

Design, Setting, and Participants

This retrospective cohort study was conducted between December 11, 2020, and July 11, 2021, with 28 days of follow-up following the week of vaccination. A novel linked database of community pharmacy and Medicare claims data was used, representing more than 50% of the US Medicare population. Community-dwelling, fee-for-service beneficiaries aged 66 years or older who received mRNA-1273 vs BNT162b2 as their first COVID-19 vaccine were identified. Data analysis began on October 18, 2022.

Exposure

Dose 1 of mRNA-1273 vs BNT162b2 vaccine.

Main Outcomes and Measures

Twelve potential adverse events (eg, pulmonary embolism, thrombocytopenia purpura, and myocarditis) were assessed individually. Frailty was measured using a claims-based frailty index, with beneficiaries being categorized as nonfrail, prefrail, and frail. The risk of diagnosed COVID-19 was assessed as a secondary outcome. Generalized linear models estimated covariate-adjusted risk ratios (RRs) and risk differences (RDs) with 95% CIs.

Results

This study included 6 388 196 eligible individuals who received the mRNA-1273 or BNT162b2 vaccine. Their mean (SD) age was 76.3 (7.5) years, 59.4% were women, and 86.5% were White. A total of 38.1% of individuals were categorized as prefrail and 6.0% as frail. The risk of all outcomes was low in both vaccine groups. In adjusted models, the mRNA-1273 vaccine was associated with a lower risk of pulmonary embolism (RR, 0.96 [95% CI, 0.93-1.00]; RD, 9 [95% CI, 1-16] events per 100 000 persons) and other adverse events in subgroup analyses (eg, 11.0% lower risk of thrombocytopenia purpura among individuals categorized as nonfrail). The mRNA-1273 vaccine was also associated with a lower risk of diagnosed COVID-19 (RR, 0.86 [95% CI, 0.83-0.87]), a benefit that was attenuated by frailty level (frail: RR, 0.94 [95% CI, 0.89-0.99]).

Conclusions and Relevance

In this cohort study of older US adults, the mRNA-1273 vaccine was associated with a slightly lower risk of several adverse events compared with BNT162b2, possibly due to greater protection against COVID-19. Future research should seek to formally disentangle differences in vaccine safety and effectiveness and consider the role of frailty in assessments of COVID-19 vaccine performance.

Leveraging Influenza Virus Surveillance From 2012 to 2015 to Characterize the Burden of Respiratory Syncytial Virus Disease in Canadian Adults ≥50 Years of Age Hospitalized With Acute Respiratory Illness

Background

Respiratory syncytial virus (RSV) disease in older adults is undercharacterized. To help inform future immunization policies, this study aimed to describe the disease burden in Canadian adults aged ≥50 years hospitalized with RSV.

Methods

Using administrative data and nasopharyngeal swabs collected from active surveillance among adults aged ≥50 years hospitalized with an acute respiratory illness (ARI) during the 2012-2013, 2013-2014, and 2014-2015 influenza seasons, RSV was identified using a respiratory virus multiplex polymerase chain reaction test to describe the associated disease burden, incidence, and healthcare costs.

Results

Of 7797 patients tested, 371 (4.8%) were RSV positive (2.2% RSV-A and 2.6% RSV-B). RSV prevalence varied by season from 4.2% to 6.2%. Respiratory virus coinfection was observed in 11.6% (43/371) of RSV cases, with influenza A being the most common. RSV hospitalization rates varied between seasons and increased with age, from 8-12 per 100 000 population in adults aged 50-59 years to 174-487 per 100 000 in adults aged ≥80 years. The median age of RSV cases was 74.9 years, 63.7% were female, and 98.1% of cases had ≥1 comorbidity. Among RSV cases, the mean length of hospital stay was 10.6 days, 13.7% were admitted to the intensive care unit, 6.4% required mechanical ventilation, and 6.1% died. The mean cost per RSV case was $13 602 (Canadian dollars) but varied by age and Canadian province.

Conclusions

This study adds to the growing literature on adult RSV burden by showing considerable morbidity, mortality, and healthcare costs in hospitalized adults aged ≥50 years with ARIs such as influenza.

The impact of pre-existing influenza antibodies and inflammatory status on the influenza vaccine responses in older adults

Age-associated immune changes and pre-existing influenza immunity are hypothesized to reduce influenza vaccine effectiveness in older adults, although the contribution of each factor is unknown. Here, we constructed influenza-specific IgG landscapes and determined baseline concentrations of cytokines typically associated with chronic inflammation in older adults (TNF-α, IL-10, IL-6, and IFN-γ) in 30 high and 29 low influenza vaccine responders (HR and LR, respectively). In a background of high H3 antibody titers, vaccine-specific H3, but not H1, antibody titers were boosted in LRs to titers comparable to HRs. Pre-vaccination concentrations of IL-10 were higher in LRs compared with HRs and inversely correlated with titers of pre-existing influenza antibodies. Baseline TNF-α concentrations were positively correlated with fold-increases in antibody titers in HRs. Our findings indicate that baseline inflammatory status is an important determinant for generating post-vaccination hemagglutinin-inhibition antibodies in older adults, and IgG responses can be boosted in the context of high pre-existing immunity.

Aging and chronic inflammation: highlights from a multidisciplinary workshop

Aging is a gradual, continuous series of natural changes in biological, physiological, immunological, environmental, psychological, behavioral, and social processes. Aging entails changes in the immune system characterized by a decrease in thymic output of naïve lymphocytes, an accumulated chronic antigenic stress notably caused by chronic infections such as cytomegalovirus (CMV), and immune cell senescence with acquisition of an inflammatory senescence-associated secretory phenotype (SASP). For this reason, and due to the SASP originating from other tissues, aging is commonly accompanied by low-grade chronic inflammation, termed "inflammaging". After decades of accumulating evidence regarding age-related processes and chronic inflammation, the domain now appears mature enough to allow an integrative reinterpretation of old data. Here, we provide an overview of the topics discussed in a recent workshop "Aging and Chronic Inflammation" to which many of the major players in the field contributed. We highlight advances in systematic measurement and interpretation of biological markers of aging, as well as their implications for human health and longevity and the interventions that can be envisaged to maintain or improve immune function in older people.

Age Differences in Comorbidities, Presenting Symptoms, and Outcomes of Influenza Illness Requiring Hospitalization: A Worldwide Perspective From the Global Influenza Hospital Surveillance Network

Background

The Global Influenza Hospital Surveillance Network (GIHSN) was established in 2012 to conduct coordinated worldwide influenza surveillance. In this study, we describe underlying comorbidities, symptoms, and outcomes in patients hospitalized with influenza.

Methods

Between November 2018 and October 2019, GIHSN included 19 sites in 18 countries using a standardized surveillance protocol. Influenza infection was laboratory-confirmed with reverse-transcription polymerase chain reaction. A multivariate logistic regression model was utilized to analyze the extent to which various risk factors predict severe outcomes.

Results

Of 16 022 enrolled patients, 21.9% had laboratory-confirmed influenza; 49.2% of influenza cases were A/H1N1pdm09. Fever and cough were the most common symptoms, although they decreased with age (P < .001). Shortness of breath was uncommon among those <50 years but increased with age (P < .001). Middle and older age and history of underlying diabetes or chronic obstructive pulmonary disease were associated with increased odds of death and intensive care unit (ICU) admission, and male sex and influenza vaccination were associated with lower odds. The ICU admissions and mortality occurred across the age spectrum.

Conclusions

Both virus and host factors contributed to influenza burden. We identified age differences in comorbidities, presenting symptoms, and adverse clinical outcomes among those hospitalized with influenza and benefit from influenza vaccination in protecting against adverse clinical outcomes. The GIHSN provides an ongoing platform for global understanding of hospitalized influenza illness.

The effect of metformin on influenza vaccine responses in nondiabetic older adults: a pilot trial

BACKGROUND

Aging is associated with progressive declines in immune responses leading to increased risk of severe infection and diminished vaccination responses. Influenza (flu) is a leading killer of older adults despite availability of seasonal vaccines. Geroscience-guided interventions targeting biological aging could offer transformational approaches to reverse broad declines in immune responses with aging. Here, we evaluated effects of metformin, an FDA approved diabetes drug and candidate anti-aging drug, on flu vaccination responses and markers of immunological resilience in a pilot and feasibility double-blinded placebo-controlled study.

RESULTS

Healthy older adults (non-diabetic/non-prediabetic, age: 74.4 ± 1.7 years) were randomized to metformin (n = 8, 1500 mg extended release/daily) or placebo (n = 7) treatment for 20 weeks and were vaccinated with high-dose flu vaccine after 10 weeks of treatment. Peripheral blood mononuclear cells (PBMCs), serum, and plasma were collected prior to treatment, immediately prior to vaccination, and 1, 5, and 10 weeks post vaccination. Increased serum antibody titers were observed post vaccination with no significant differences between groups. Metformin treatment led to trending increases in circulating T follicular helper cells post-vaccination. Furthermore, 20 weeks of metformin treatment reduced expression of exhaustion marker CD57 in circulating CD4 T cells.

CONCLUSIONS

Pre-vaccination metformin treatment improved some components of flu vaccine responses and reduced some markers of T cell exhaustion without serious adverse events in nondiabetic older adults. Thus, our findings highlight the potential utility of metformin to improve flu vaccine responses and reduce age-related immune exhaustion in older adults, providing improved immunological resilience in nondiabetic older adults.

COVID-19 and Frailty

Older age is a major risk factor for adverse outcomes of COVID-19, potentially due to immunosenescence and chronic low-grade inflammation, both characteristics of older adults which synergistically contribute to their vulnerability. Furthermore, older age is also associated with decreased kidney function and is consequently associated with an increased risk of cardiovascular disease. All of this in the course of COVID-19 infection can worsen and promote the progression of chronic kidney damage and all its sequelae. Frailty is a condition characterized by the decline in function of several homeostatic systems, leading to increased vulnerability to stressors and risk of adverse health outcomes. Thus, it is very likely that frailty, together with comorbidities, may have contributed to the high vulnerability to severe clinical manifestations and deaths from COVID-19 among older people. The combination of viral infection and chronic inflammation in the elderly could cause multiple unforeseen harmful consequences, affecting overall disability and mortality rates. In post-COVID-19 patients, inflammation has been implicated in sarcopenia progression, functional activity decline, and dementia. After the pandemic, it is imperative to shine a spotlight on these sequelae so that we can be prepared for the future outcomes of the ongoing pandemic. Here, we discuss the potential long-term consequences of SARS-CoV-2 infection and its possibility of causing permanent damage to the precarious balance existing in the frail elderly with multiple pathologies.

Frailty impacts immune responses to Moderna COVID-19 mRNA vaccine in older adults

BACKGROUND

Immune responses to COVID-19 mRNA vaccines have not been well characterized in frail older adults. We postulated that frailty is associated with impaired antibody and cellular mRNA vaccine responses.

METHODS

We followed older adults in a retirement facility with longitudinal clinical and serological samples from the first Moderna mRNA-1273 vaccine dose starting in February 2021 through their 3rd (booster) vaccine dose. Outcomes were antibody titers, antibody avidity, and AIM+ T cell function and phenotype. Statistical analysis used linear regression with clustered error for antibody titers over multiple timepoints with clinical predictors including, age, sex, prior infection status, and clinical frailty scale (CFS) score. T cell function analysis used linear regression models with clinical predictors and cellular memory phenotype variables.

RESULTS

Participants (n = 15) had median age of 90 years and mild, moderate, or severe frailty scores (n = 3, 7, or 5 respectively). Over the study time course, anti-spike antibody titers were 10-fold higher in individuals with lower frailty status (p = 0.001 and p = 0.005, unadjusted and adjusted for prior COVID-19 infection). Following the booster, titers to spike protein improved regardless of COVID-19 infection or degree of frailty (p = 0.82 and p = 0.29, respectively). Antibody avidity significantly declined over 6 months in all participants following 2 vaccine doses (p < 0.001), which was further impaired with higher frailty (p = 0.001). Notably, avidity increased to peak levels after the booster (p < 0.001). Overall antibody response was inversely correlated with a phenotype of immune-senescent T cells, CD8 + CD28- TEMRA cells (p = 0.036, adjusted for COVID-19 infection). Furthermore, there was increased detection of CD8 + CD28- TEMRA cells in individuals with greater frailty (p = 0.056, adjusted for COVID-19).

CONCLUSIONS

We evaluated the immune responses to the Moderna COVID-19 mRNA vaccine in frail older adults in a retirement community. A higher degree of frailty was associated with diminished antibody quantity and quality. However, a booster vaccine dose at 6 months overcame these effects. Frailty was associated with an increased immune-senescence phenotype that may contribute to the observed changes in the vaccine response. While the strength of our conclusions was limited by a small cohort, these results are important for guiding further investigation of vaccine responses in frail older adults.

Associations of influenza and pneumococcal vaccinations with burdens of older family caregivers: The Japan Gerontological Evaluation study (JAGES) cross-sectional study

BACKGROUND

Influenza and pneumonia tend to be severe in older adults; thus, vaccination is necessary to prevent these illnesses. Vaccination is especially important for older family caregivers (OFCs) not only to prevent them from becoming ill, but also to prevent secondary infections in the family care receivers (FCRs), who are mostly frail older adults and have a higher risk of severe illness. Thus, we investigated whether caregiving burdens were associated with the vaccinations among older adults.

METHODS

We used cross-sectional data from the Japan Gerontological Evaluation Study (JAGES), which was conducted in 64 Japanese municipalities from November 2019 to January 2020. The target population consisted of 26,177 individuals aged 65 years or older who were independent and did not need public long-term care. The primary outcome was the uptakes of either or both influenza and pneumococcal vaccinations. Multinomial logistic regressions were performed, setting those who underwent neither vaccinations as the reference group.

RESULTS

Among the participants, 23.3 %, 25.8 %, 9.4 %, or 41.5 % underwent neither, only influenza, only pneumococcal, or the both vaccinations, respectively. The caregiving frequency, time length in a day, or dementia of FCR were negatively associated with influenza vaccination (caregiving almost every day: relative risk ratio {RRR}: 0.39, 95 % confident interval {95 % CI} [0.24-0.63]; caregiving almost all day: 0.44, 95 % CI: 0.23-0.85; caregiving for FCR: RRR:0.55, 95 % CI: 0.34-0.91). On the other hand, those caregiving burdens were not associated with pneumococcal only or the both vaccinations. Having a family physician mitigated all the negative effect of the caregiving burdens on the vaccinations.

CONCLUSION

Our results suggest that the caregiving burden is a barrier to influenza vaccination but not to pneumococcal vaccination and that having a physician mitigates the negative effect regardless of the burden kind.

Frailty and Humoral Immune Responses Following COVID-19 Vaccination among Patients Undergoing Hemodialysis

BACKGROUND

Patients with end-stage kidney disease who are undergoing dialysis have reduced immune responses to COVID-19 vaccination. Frailty is extremely common among dialysis patients and may contribute to the impaired immunogenicity. This study aimed to determine the association between frailty and humoral immune responses following COVID-19 vaccination in hemodialysis patients.

DESIGN, SETTING, PARTICIPANTS

Adult hemodialysis patients without prior SARS-CoV-2 infection who received a priming dose of ChAdOx1 nCoV-19, an adenovirus-vectored vaccine, were assessed for eligibility. Participants were categorized as robust, pre-frail, or frail using the Fried frailty criteria. Humoral responses were assessed 28 days after vaccination by measuring titers of anti-spike IgG antibodies. The primary outcome was anti-spike antibody seroconversion, defined as antibody levels ≥50 AU/mL. Multivariable-adjusted logistic regression models were used to assess the association between frailty status and the primary outcome.

RESULTS

A total of 206 participants (mean age 67 ± 13 years, 50% women) were included in the study, of whom 50 (24%) were characterized as frail, 86 (42%) were characterized as pre-frail, and 70 (34%) were characterized as robust. Anti-spike antibody levels were progressively lower with more advanced stages of frailty (P <0.001). Compared with robust patients, a significantly smaller proportion of pre-frail and frail patients developed anti-spike antibody seroconversion (87%, 66%, and 40%, respectively; P <0.001). Frailty was associated with the absence of humoral responses after adjustment for age, sex, body mass index, diabetes, coronary artery disease, serum albumin, and lymphocyte count (OR=0.25; 95% CI, 0.08-0.80).

CONCLUSIONS

Frailty is independently associated with impaired humoral responses following COVID-19 vaccination among hemodialysis patients. Strategies aimed at preventing or attenuating frailty in the dialysis population are warranted.

Frailty Reduces Vaccine Effectiveness Against SARS-CoV-2 Infection: A Test-Negative Case Control Study Using National VA Data

OBJECTIVES

To assess the variation of vaccine effectiveness against SARS-CoV-2 infection during the Delta wave according to frailty status among U.S. veterans.

DESIGN

Test-negative case-control study of SARS-CoV-2 mRNA vaccine effectiveness.

SETTING

Veterans Health Administration (VHA) medical centers.

PARTICIPANTS

Veterans 19 years and older who had at least one COVID-19/Flu like symptoms and received a SARS-CoV-2 PCR or antigen test at VHA medical centers between July 25 to September 30, 2021.

INTERVENTION

mRNA vaccination.

MEASUREMENTS

New SARS-CoV-2 infection. Vaccine effectiveness was defined as 1-odds of vaccination in cases/odds of vaccination in controls, where cases were patients who had a COVID-19 test and tested positive for SARS-CoV-2, and controls were those who tested negative. Frailty was measured using the VA frailty index, categorized as robust (0-<0.1), pre-frail (≥0.1-<0.21) and frail (≥0.21).

RESULTS

A total of 58,604 patients (age:58.9±17.0, median:61, IQR:45-72; 87.5%men; 68.1%white; 1.3%African American, 8.3%Hispanic) were included in the study. Of these, 27,733 (47.3%) were robust, 16,276 (27.8%) were prefrail, and 14,595 (24.9%) were frail. mRNA vaccine effectiveness against the Delta variant symptomatic infection was lower in patients with frailty, 62.8 %(95%CI:59.8-65.7), versus prefrail 73.9%(95%CI:72.0-75.7), and robust, 77.0 %(95%CI:75.7-78.3).

CONCLUSIONS

This test-negative case control study showed that mRNA vaccine effectiveness against infection declined in veterans with frailty. Frailty status is a factor to consider when designing, developing, and evaluating COVID-19 vaccines.

Investigating confounding in network-based test-negative design influenza vaccine effectiveness studies-Experience from the DRIVE project

BACKGROUND

Establishing a large study network to conduct influenza vaccine effectiveness (IVE) studies while collecting appropriate variables to account for potential bias is important; the most relevant variables should be prioritized. We explored the impact of potential confounders on IVE in the DRIVE multi-country network of sites conducting test-negative design (TND) studies.

METHODS

We constructed a directed acyclic graph (DAG) to map the relationship between influenza vaccination, medically attended influenza infection, confounders, and other variables. Additionally, we used the Development of Robust and Innovative Vaccines Effectiveness (DRIVE) data from the 2018/2019 and 2019/2020 seasons to explore the effect of covariate adjustment on IVE estimates. The reference model was adjusted for age, sex, calendar time, and season. The covariates studied were presence of at least one, two, or three chronic diseases; presence of six specific chronic diseases; and prior healthcare use. Analyses were conducted by site and subsequently pooled.

RESULTS

The following variables were included in the DAG: age, sex, time within influenza season and year, health status and comorbidities, study site, health-care-seeking behavior, contact patterns and social precautionary behavior, socioeconomic status, and pre-existing immunity. Across all age groups and settings, only adjustment for lung disease in older adults in the primary care setting resulted in a relative change of the IVE point estimate >10%.

CONCLUSION

Our study supports a parsimonious approach to confounder adjustment in TND studies, limited to adjusting for age, sex, and calendar time. Practical implications are that necessitating fewer variables lowers the threshold for enrollment of sites in IVE studies and simplifies the pooling of data from different IVE studies or study networks.

Markers of systemic inflammation are positively associated with influenza vaccine antibody responses with a possible role for ILT2(+)CD57(+) NK-cells

Background

With increasing age, overall health declines while systemic levels of inflammatory mediators tend to increase. Although the underlying mechanisms are poorly understood, there is a wealth of data suggesting that this so-called “inflammaging” contributes to the risk of adverse outcomes in older adults. We sought to determine whether markers of systemic inflammation were associated with antibody responses to the seasonal influenza vaccine.

Results

Over four seasons, hemagglutination inhibition antibody titres and ex vivo bulk peripheral blood mononuclear cell (PBMC) responses to live influenza viruses assessed via interferon (IFN)-γ/interleukin (IL)-10 production, were measured pre- and 4-weeks post-vaccination in young adults (n = 79) and older adults randomized to standard- or high-dose inactivated vaccine (n = 612). Circulating tumour necrosis factor (TNF), interleukin (IL)-6 and C-reactive protein (CRP) were also measured pre-vaccination. Post-vaccination antibody titres were significantly associated with systemic inflammatory levels; specifically, IL-6 was positively associated with A/H3N2 titres in young adults (Cohen’s d = 0.36), and in older high-dose, but not standard-dose recipients, all systemic inflammatory mediators were positively associated with A/H1N1, A/H3N2 and B titres (d = 0.10–0.45). We further show that the frequency of ILT2(+)CD57(+) CD56-Dim natural killer (NK)-cells was positively associated with both plasma IL-6 and post-vaccination A/H3N2 titres in a follow-up cohort of older high-dose recipients (n = 63). Pathway analysis suggested that ILT2(+)CD57(+) Dim NK-cells mediated 40% of the association between IL-6 and A/H3N2 titres, which may be related to underlying participant frailty.

Conclusions

In summary, our data suggest a complex relationship amongst influenza vaccine responses, systemic inflammation and NK-cell phenotype in older adults, which depends heavily on age, vaccine dose and possibly overall health status. While our results suggest that “inflammaging” may increase vaccine immunogenicity in older adults, it is yet to be determined whether this enhancement contributes to improved protection against influenza disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12979-022-00284-x.

How aging impacts vaccine efficacy: known molecular and cellular mechanisms and future directions

Aging leads to a gradual dysregulation of immune functions, one consequence of which is reduced vaccine efficacy. In this review, we discuss several key contributing factors to the age-related decline in vaccine efficacy, such as alterations within the lymph nodes where germinal center (GC) reactions take place, alterations in the B cell compartment, alterations in the T cell compartment, and dysregulation of innate immune pathways. Additionally, we discuss several methods currently used in vaccine development to bolster vaccine efficacy in older adults. This review highlights the multifactorial defects that impair vaccine responses with aging.

Effectiveness estimates for enhanced trivalent influenza vaccines in an aged care summer outbreak

An influenza outbreak occurred during summer (February 2019) in an aged-care facility in Sydney, Australia. Residents had not received the annual 2019 influenza vaccine while 76.7% had received 2018 influenza vaccines about 9 months prior. Overall, 2018 influenza vaccine effectiveness during this outbreak was high (93.6%). The effectiveness of the high-dose trivalent vaccine (HD-TIV) and adjuvanted trivalent (a-TIV) vaccine were 89.8% (95% confidence interval: 18.8%-98.7%) and 72.5% (95% confidence interval: -106.7%-96.3%) respectively. The differences in effectiveness between HD-TIV, a-TIV and SD-QIV, during the summer outbreak were not significant.

COVID-19 mRNA vaccine effectiveness against hospitalisation and death in veterans according to frailty status during the SARS-CoV-2 delta (B.1.617.2) variant surge in the USA: a retrospective cohort study

Background

Studies have shown that COVID-19 vaccination is effective at preventing infection and death in older populations. However, whether vaccination effectiveness is reduced in patients with frailty is unclear. We aimed to compare vaccine effectiveness against hospitalisation and death after COVID-19 during the surge of the delta (B.1.617.2) variant of SARS-CoV-2 according to patients' frailty status.

Methods

In this retrospective cohort study, we used data derived from the US Veterans Health Administration (VHA) facilities and the US Department of Veterans Affairs (VA) COVID-19 Shared Data Resource, which contains information from the VA National Surveillance Tool, death certificates, and National Cemetery Administration. We included veterans aged 19 years or older who tested positive for SARS-CoV-2 using RT-PCR or antigen tests between July 25 and Sept 30, 2021, with no record of a previous positive test. Deaths were identified through VHA facilities, death certificates, and National Cemetery Administration data available from VA databases. We also retrieved data including sociodemographic characteristics, medical conditions diagnosed at baseline, frailty score, and vaccination information. The primary outcomes were COVID-19-associated hospitalisations and all-cause deaths at 30 days from testing positive for SARS-CoV-2. The odds ratio (OR) for COVID-19-associated hospitalisation and hazard ratio (HR) for death of vaccinated patients compared with the unvaccinated patients were estimated according to frailty categories of robust, pre-frail, or frail. Vaccine effectiveness was estimated as 1 minus the OR for COVID-19-associated hospitalisation, and 1 minus the HR for death.

Findings

We identified 57 784 veterans (mean age 57·5 years [SD 16·7], 50 642 [87·6%] males, and 40 743 [70·5%] White people), of whom 28 497 (49·3%) were categorised as robust, 16 737 (29·0%) as pre-frail, and 12 550 (21·7%) as frail. There were 2577 all-cause deaths (676 [26·2%] in the vaccinated group and 1901 [73·8%] in the unvaccinated group), and 7857 COVID-19-associated hospitalisations (2749 [35·0%] in the vaccinated group and 5108 [65·0%] in the unvaccinated group) within 30 days of a positive SARS-CoV-2 test. Vaccine effectiveness against COVID-19-associated hospitalisation within 30 days of a positive SARS-CoV-2 test was 65% (95% CI 61-69) in the robust group, 54% (48-58) in the pre-frail group, and 36% (30-42) in the frail group. By 30 days of a positive SARS-CoV-2 test, the vaccine effectiveness for all-cause death was 79% (95% CI 74-84) in the robust group, 79% (75-83) in the pre-frail group, and 68% (63-71) in the frail group.

Interpretation

Compared with non-frail patients (pre-frail and robust), those with frailty had lower levels of vaccination protection against COVID-19-associated hospitalisation and all-cause death. Future studies investigating COVID-19 vaccine effectiveness should incorporate frailty assessments and actively recruit older adults with frailty.

Funding

Miami VA Healthcare System Geriatric Research Education and Clinical Center.

An Easy-to-Implement Clinical-Trial Frailty Index Based on Accumulation of Deficits: Validation in Zoster Vaccine Clinical Trials

Purpose

Despite being among those most in need of protection, frail older adults are often not well represented in clinical trials. Although frailty likely influences responses to treatments and vaccines, frailty may not be explicitly considered in trials even when frail participants are enrolled due to the perception that frailty is difficult to measure effectively and efficiently without adding to participant or data collection burden. We developed an easy-to-implement frailty index, the Clinical Trial-Frailty Index (CT-FI), based on baseline medical history and standard patient-reported outcomes using data from clinical trials of recombinant Zoster vaccine (the ZOE-50 and ZOE-70 studies). Our objective was to demonstrate that the CT-FI is a robust measure that may be used retrospectively or prospectively in clinical trials where sufficient patient data have been collected.

Methods

The CT-FI was based on baseline medical history and Quality of Life questionnaires (SF-36 and EQ-5D). Items meeting criteria for inclusion were scored from 0 to 1, then summed for each participant and divided by the total number of deficits considered. Validation analyses included descriptive verification of distribution and age- and sex-associations in relation to usual patterns of the frailty index, regressions in relation to outcomes hypothesized to be related to frailty, and resampling methods within the index.

Results

The CT-FI distribution was well represented by a gamma distribution with a range of 0–0.70. Deficit accumulation increased with chronological age and was higher for females. Multivariate Cox regression survival analysis showed that the CT-FI, age, and sex were significant predictors of mortality. Jackknife and Bootstrap resampling methods highlighted the robustness of the CT-FI, which was not sensitive to inclusion/exclusion of specific individual or groups of variables.

Conclusion

We have developed a reliable, robust and easy-to-implement CT-FI with potential retrospective or prospective application in other clinical trials.

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Advanced biological age is associated with improved antibody responses in older high-dose influenza vaccine recipients over four consecutive seasons

Background

Biological aging represents a loss of integrity and functionality of physiological systems over time. While associated with an enhanced risk of adverse outcomes such as hospitalization, disability and death following infection, its role in perceived age-related declines in vaccine responses has yet to be fully elucidated. Using data and biosamples from a 4-year clinical trial comparing immune responses of standard- and high-dose influenza vaccination, we quantified biological age (BA) prior to vaccination in adults over 65 years old (n = 292) using a panel of ten serological biomarkers (albumin, alanine aminotransferase, creatinine, ferritin, free thyroxine, cholesterol, high-density lipoprotein, triglycerides, tumour necrosis factor, interleukin-6) as implemented in the BioAge R package. Hemagglutination inhibition antibody titres against influenza A/H1N1, A/H3N2 and B were quantified prior to vaccination and 4-, 10- and 20- weeks post-vaccination.

Results

Counter to our hypothesis, advanced BA was associated with improved post-vaccination antibody titres against the different viral types and subtypes. However, this was dependent on both vaccine dose and CMV serostatus, as associations were only apparent for high-dose recipients (d = 0.16–0.26), and were largely diminished for CMV positive high-dose recipients.

Conclusions

These findings emphasize two important points: first, the loss of physiological integrity related to biological aging may not be a ubiquitous driver of immune decline in older adults; and second, latent factors such as CMV infection (prevalent in up to 90% of older adults worldwide) may contribute to the heterogeneity in vaccine responses of older adults more than previously thought.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12979-022-00296-7.

Frailty and Age Impact Immune Responses to Moderna COVID-19 mRNA Vaccine

BACKGROUND

Immune responses to COVID-19 mRNA vaccines have not been well characterized in frail older adults. We postulated that frailty is associated with impaired antibody and cellular mRNA vaccine responses.

METHODS

We followed older adults in a retirement facility with longitudinal clinical and serological samples from the first Moderna mRNA-1273 vaccine dose starting in February 2021 through their 3rd (booster) vaccine dose. Outcomes were antibody titers, antibody avidity, and AIM+ T cell function and phenotype. Statistical analysis used antibody titers in linear mixed-effects linear regression with clinical predictors including, age, sex, prior infection status, and clinical frailty scale (CFS) score. T cell function analysis used clinical predictors and cellular phenotype variables in linear regression models.

RESULTS

Participants (n=15) had median age of 90 years and mild, moderate, or severe frailty scores (n=3, 7, or 5 respectively). After 2 vaccine doses, anti-spike antibody titers were higher in 5-fold higher in individuals with mild frailty compared to severe frailty and 9-fold higher in individuals with prior COVID-19 infection compared to uninfected (p=0.02 and p<0.001). Following the booster, titers improved regardless of COVID-19 infection or frailty. Antibody avidity significantly declined following 2 vaccine doses regardless of frailty status, but reached maximal avidity after the booster. Spike-specific CD4+ T cell responses were modulated by frailty and terminally differentiated effector memory TEMRA cells, and spike-specific TFH cell responses were inversely correlated with age. Additionally, an immune-senescent memory T cell phenotype was correlated with frailty and functional decline.

CONCLUSIONS

We described the separate influences of frailty and age on adaptive immune responses to the Moderna COVID-19 mRNA vaccine. Though overall antibody responses were robust, higher frailty diminished initial antibody quantity, and all older adults had impaired antibody avidity. Following the booster, antibody responses improved, overcoming the effects of age and frailty. CD4+ T cell responses were independently impacted by age, frailty, and burden of immune-senescence. Frailty was correlated with increased burden of immune-senescence, suggesting an immune-mediated mechanism for physiological decline.

A Cohort Study on Influenza Vaccine and All-Cause Mortality in Older Adults: Methodological Concerns and Public Health Implications

Introduction

In 2020, the restrictions adopted to control the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic led to an unprecedented reduction in influenza-related burden. As such, the reduced chance to characterize the circulating virus strains might have increased the risk of vaccine mismatch for the forthcoming winter seasons. The role of an effective influenza vaccination campaign might therefore assume even more value, especially for frail and multimorbid older individuals. Methodological concerns on confounding by indication are always debated in vaccine effectiveness studies and it might be instrumental to give a pragmatic message on an individual’s responsibility to receive the influenza vaccine. We therefore investigated the role of specific confounders to explain the association between influenza vaccine and mortality among older adults.

Methods

Using a primary care database, we formed a cohort of patients aged 65 years or older who were actively registered with their general practitioner (GP) at the beginning of each of nine influenza seasons through to the 2018/2019 season. The study index date was the related seasons’ starting date. Exposure to the influenza vaccine was operationally defined in the 2 months preceding the index date up to 2 weeks before the exit date. Cox regression models were estimated to calculate hazard ratios (HRs) and their 95% confidence intervals (CI) of death between vaccinated and unvaccinated patients in a time-dependent fashion. The potential confounders sequentially entered the model based on their increasing effect size observed in univariate analyses.

Results

Over the 10 years under study, the influenza vaccine showed a significant protective effect in terms of mortality, reaching 13% reduction (HR 0.87, 95% CI 0.80–0.95) in the 2018/2019 influenza season. When we estimated the multivariate model by sequentially adding the potential confounders, there was an inversion of HR (below the unit) that was significantly explained by the covariates coding for a prior history of lower respiratory tract infections and the presence of the pneumococcal vaccine.

Conclusion

In the current pandemic scenario, we cannot divert attention to proper use of face masks, social distancing, and hand hygiene, which are important measures to prevent influenza and other respiratory viral infections. Nonetheless, their effectiveness might be negligible without acceptable coverage for influenza vaccine, especially in older patients with a history of lower respiratory tract infections, which appears to be the main source of confounding by indication.

Frailty and COVID-19 mRNA Vaccine Antibody Response in the COVID-19 Community Research Partnership

BACKGROUND

COVID-19 has disproportionately affected older adults. Frailty has been associated with impaired vaccine response in other vaccine types, but the impact of frailty on mRNA vaccine response is undefined.

METHODS

Observational study of adults aged 55 and older from 1 U.S. health care system between January 22, 2021 and September 16, 2021 with self-reported Moderna or Pfizer COVID-19 mRNA vaccine and an electronic frailty index (eFI) score from their medical record (n = 1 677). Participants' frailty status was compared with positive antibody detection (seroconversion) following full vaccination and subsequent loss of positive antibody detection (seroreversion) using logistic regression models.

RESULTS

Of 1 677 older adults with median (interquartile range) age, 67 (62 and 72) years, and frailty status (nonfrail: 879 [52%], prefrail: 678 [40%], and frail: 120 [7.2%]), seroconversion was not detected in 23 (1.4%) over 60 days following full vaccination. Frail individuals were less likely to seroconvert than nonfrail individuals, adjusted odds ratio (OR) 3.75, 95% confidence interval (CI; 1.04, 13.5). Seroreversion was detected in 50/1 631 individuals (3.1%) over 6 months of median follow-up antibody testing. Frail individuals were more likely to serorevert than nonfrail individuals, adjusted OR 3.02, 95% CI (1.17, 7.33).

CONCLUSION

Overall antibody response to COVID-19 mRNA vaccination was high across age and frailty categories. While antibody detection is an incomplete descriptor of vaccine response, the high sensitivity of this antibody combined with health-system data reinforce our conclusions that frailty is an independent predictor of impaired antibody response to the COVID-19 mRNA vaccines. Frailty should be considered in vaccine studies and prevention strategies.

The prevalence of frailty and pre-frailty among geriatric hospital inpatients and its association with economic prosperity and healthcare expenditure: A systematic review and meta-analysis of 467,779 geriatric hospital inpatients

BACKGROUND

Frailty is a common and clinically significant condition among geriatric populations. Although well-evidenced pooled estimates of the prevalence of frailty exist within various settings and populations, presently there are none assessing the overall prevalence of frailty among geriatric hospital inpatients. The purpose of this review was to systematically search and analyse the prevalence of frailty among geriatric hospital inpatients within the literature and examine its associations with national economic indicators.

METHODS

Systematic searches were conducted on Ovid, Web of Science, Scopus, CINAHL Plus, and the Cochrane Library, encompassing all literature published prior to 22 November 2018, supplemented with manual reference searches. Included studies utilised a validated operational definition of frailty, reported the prevalence of frailty, had a minimum age ≥ 65 years, attempted to assess the whole ward/clinical population, and occurred among hospital inpatients. Two reviewers independently extracted data and assessed study quality.

RESULTS

Ninety-six studies with a pooled sample of 467,779 geriatric hospital inpatients were included. The median critical appraisal score was 8/9 (range 7-9). The pooled prevalence of frailty, and pre-frailty, among geriatric hospital inpatients was 47.4% (95% CI 43.7-51.1%), and 25.8% (95% CI 22.0-29.6%), respectively. Significant differences were observed in the prevalence of frailty stratified by age, prevalent morbidity, ward type, clinical population, and operational definition. No significant differences were observed in stratified analyses by sex or continent, or significant associations between the prevalence of frailty and economic indicators.

CONCLUSIONS

Frailty is highly prevalent among geriatric hospital inpatients. High heterogeneity exists within this setting based on various clinical and demographic characteristics. Pooled estimates reported in this review place the prevalence of frailty among geriatric hospital inpatients between that reported for community-dwelling older adults and older adults in nursing homes, outlining an increase in the relative prevalence of frailty with progression through the healthcare system.

Cellular Immunity Is Critical for Assessing COVID-19 Vaccine Effectiveness in Immunocompromised Individuals

COVID-19 vaccine clinical development was conducted with unprecedented speed. Immunity measurements were concentrated on the antibody response which left significant gaps in our understanding how robust and long-lasting immune protection develops. Better understanding the cellular immune response will fill those gaps, especially in the elderly and immunocompromised populations which not only have the highest risk for severe infection, but also frequently have inadequate antibody responses. Although cellular immunity measurements are more logistically complex to conduct for clinical trials compared to antibody measurements, the feasibility and benefit of doing them in clinical trials has been demonstrated and so should be more widely adopted. Adding significant cellular response metrics will provide a deeper understanding of the overall immune response to COVID-19 vaccination, which will significantly inform vaccination strategies for the most vulnerable populations. Better monitoring of overall immunity will also substantially benefit other vaccine development efforts, and indeed any therapies that involve the immune system as part of the therapeutic strategy.

Immunosenescence and Altered Vaccine Efficiency in Older Subjects: A Myth Difficult to Change

Organismal ageing is associated with many physiological changes, including differences in the immune system of most animals. These differences are often considered to be a key cause of age-associated diseases as well as decreased vaccine responses in humans. The most often cited vaccine failure is seasonal influenza, but, while it is usually the case that the efficiency of this vaccine is lower in older than younger adults, this is not always true, and the reasons for the differential responses are manifold. Undoubtedly, changes in the innate and adaptive immune response with ageing are associated with failure to respond to the influenza vaccine, but the cause is unclear. Moreover, recent advances in vaccine formulations and adjuvants, as well as in our understanding of immune changes with ageing, have contributed to the development of vaccines, such as those against herpes zoster and SARS-CoV-2, that can protect against serious disease in older adults just as well as in younger people. In the present article, we discuss the reasons why it is a myth that vaccines inevitably protect less well in older individuals, and that vaccines represent one of the most powerful means to protect the health and ensure the quality of life of older adults.

Effectiveness of influenza vaccination in the elderly: a population-based case-crossover study

BACKGROUND

There is limited information regarding the effectiveness of influenza vaccines for older adults. Particularly, controlling for healthy senior bias is challenging in observational studies. We aimed to assess the efficacy of influenza vaccination in the elderly while addressing potential healthy senior bias and whether it was related to virus-vaccine strains matching.

METHOD

To control between-individual confounder, we used a case-crossover study design using Taiwan's National Health Insurance Research Dataset to analyse the association between influenza vaccination in older adults and the risk of hospitalisation for community-acquired pneumonia (CAP). Individuals were a 'case' in vaccinated years and a 'control' in unvaccinated years. The study periods were 2006/2007 and 2007/2008 seasons because virus-vaccine strains were matching in 2006/2007 season and unmatching in 2007/2008 season. Older adults were categorised into two groups: admitted for CAP during the pre-vaccination period (Admitted, n=311) and not hospital admitted for CAP (Non-admitted, n=572 432). The outcome was hospitalisation for CAP during the influenza period. Conditional logistic regression assessed influenza vaccine efficacy in reducing CAP.

RESULTS

Influenza vaccination had no protective effects in Admitted group. However, because of the tiny numbers in Admitted group, we could draw very limited conclusions. Receiving an influenza vaccine significantly prevented CAP in Non-admitted group only during the vaccine-circulating strain-matched year (OR, 0.72; 95% CI, 0.64 to 0.83). In addition, there was no protective effect against CAP hospitalisation among individuals with a Charlson Comorbidity Index score over 2.

CONCLUSION

Influenza vaccine efficacy was associated with vaccine-circulating strain-matched. When vaccine-circulating strains were all matching, receiving a shot reduced the probability of CAP hospitalisation by 28% in Non-admitted group. However, high comorbidity may reduce the vaccine efficacy. Therefore, it is necessary to educate older adults to receive annual influenza vaccination and in combination with non-pharmaceutical interventions to reduce the risk of CAP.

Roadmap for Sex-Responsive Influenza and COVID-19 Vaccine Research in Older Adults

Sex differences in the immune system are dynamic throughout the lifespan and contribute to heterogeneity in the risk of infectious diseases and the response to vaccination in older adults. The importance of the intersection between sex and age in immunity to viral respiratory diseases is clearly demonstrated by the increased prevalence and severity of influenza and COVID-19 in older males compared to older females. Despite sex and age biases in the epidemiology and clinical manifestations of disease, these host factors are often ignored in vaccine research. Here, we review sex differences in the immunogenicity, effectiveness, and safety of the influenza and COVID-19 vaccines in older adults and the impact of sex-specific effects of age-related factors, including chronological age, frailty, and the presence of comorbidities. While a female bias in immunity to influenza vaccines has been consistently reported, understanding of sex differences in the response to COVID-19 vaccines in older adults is incomplete due to small sample sizes and failure to disaggregate clinical trial data by both sex and age. For both vaccines, a major gap in the literature is apparent, whereby very few studies investigate sex-specific effects of aging, frailty, or multimorbidity. By providing a roadmap for sex-responsive vaccine research, beyond influenza and COVID-19, we can leverage the heterogeneity in immunity among older adults to provide better protection against vaccine-preventable diseases.

Safety & effectiveness of COVID-19 vaccines: A narrative review

There are currently eight vaccines against SARS-CoV-2 that have received Emergency Use Authorization by the WHO that can offer some protection to the world's population during the COVID-19 pandemic. Though research is being published all over the world, public health officials, policymakers and governments are collecting evidence-based information to establish the public health policies. Unfortunately, continued international travel, violations of lockdowns and social distancing, the lack of mask use, the emergence of mutant strains of the virus and lower adherence by a sector of the global population that remains sceptical of the protection offered by vaccines, or about any risks associated with vaccines, hamper these efforts. Here we examine the literature on the efficacy, effectiveness and safety of COVID-19 vaccines, with an emphasis on select categories of individuals and against new SARS-CoV-2 strains. The literature shows that these eight vaccines are highly effective in protecting the population from severe disease and death, but there are some issues concerning safety and adverse effects. Further, booster shots and variant-specific vaccines would also be required.

How frail is frail? A systematic scoping review and synthesis of high impact studies

AIMS

While the frailty index (FI) is a continuous variable, an FI score of 0.25 has construct and predictive validity to categorise community-dwelling older adults as frail or non-frail. Our study aimed to explore which FI categories (FI scores and labels) were being used in high impact studies of adults across different care settings and why these categories were being chosen by study authors.

METHODS

For this systematic scoping review, Medline, Cochrane and EMBASE databases were searched for studies that measured and categorised an FI. Of 1314 articles screened, 303 met the eligibility criteria (community: N = 205; residential aged care: N = 24; acute care: N = 74). For each setting, the 10 studies with the highest field-weighted citation impact (FWCI) were identified and data, including FI scores and labels and justification provided, were extracted and analysed.

RESULTS

FI scores used to distinguish frail and non-frail participants varied from 0.12 to 0.45 with 0.21 and 0.25 used most frequently. Additional categories such as mildly, moderately and severely frail were defined inconsistently. The rationale for selecting particular FI scores and labels were reported in most studies, but were not always relevant.

CONCLUSIONS

High impact studies vary in the way they categorise the FI and while there is some evidence in the community-dweller literature, FI categories have not been well validated in acute and residential aged care. For the time being, in those settings, the FI should be reported as a continuous variable wherever possible. It is important to continue working towards defining frailty categories as variability in FI categorisation impacts the ability to synthesise results and to translate findings into clinical practice.