Influenza vaccine responses in older adults

Influenza A(H3N2) Antibody Responses to Standard-Dose Versus Enhanced Influenza Vaccine Immunogenicity in Older Adults and Prior Season's Vaccine Status

BACKGROUND

Annual influenza vaccination is recommended for older adults but repeated vaccination with standard-dose influenza vaccine has been linked to reduced immunogenicity and effectiveness, especially against A(H3N2) viruses.

METHODS

Community-dwelling Hong Kong adults aged 65-82 years were randomly allocated to receive 2017-2018 standard-dose quadrivalent, MF59-adjuvanted trivalent, high-dose trivalent, and recombinant-HA quadrivalent vaccination. Antibody response to unchanged A(H3N2) vaccine antigen was compared among participants with and without self-reported prior year (2016-2017) standard-dose vaccination.

RESULTS

Mean fold rise (MFR) in antibody titers from day 0 to day 30 by hemagglutination inhibition and virus microneutralization assays were lower among 2017-2018 standard-dose and enhanced vaccine recipients with (range, 1.7-3.0) versus without (range, 4.3-14.3) prior 2016-2017 vaccination. MFR was significantly reduced by about one-half to four-fifths for previously vaccinated recipients of standard-dose and all 3 enhanced vaccines (β range, .21-.48). Among prior-year vaccinated older adults, enhanced vaccines induced higher 1.43 to 2.39-fold geometric mean titers and 1.28 to 1.74-fold MFR versus standard-dose vaccine by microneutralization assay.

CONCLUSIONS

In the context of unchanged A(H3N2) vaccine strain, prior-year vaccination was associated with reduced antibody response among both standard-dose and enhanced influenza vaccine recipients. Enhanced vaccines improved antibody response among older adults with prior-year standard-dose vaccination.

Longitudinal analysis of influenza vaccination implicates regulation of RIG-I signaling by DNA methylation

Influenza virus infection alters the promoter DNA methylation of key immune response-related genes, including type-1 interferons and proinflammatory cytokines. However, less is known about the effect of the influenza vaccine on the epigenome. We utilized a targeted DNA methylation approach to study the longitudinal effects (day 0 pre-vaccination and day 28 post-vaccination) on influenza vaccination responses in peripheral blood mononuclear cells. We found that baseline, pre-vaccination methylation profiles are associated with pre-existing, protective serological immunity. Additionally, we identified 481 sites that were differentially methylated between baseline and day 28 post-vaccination. These were enriched for genes involved in the regulation of the RIG-I signaling pathway, an important regulator of viral responses. Our results suggest that DNA methylation changes to components of the RIG-I pathway are associated with vaccine effectiveness. Therefore, immunization strategies that target this pathway may improve serological responses to influenza vaccination.

Estimated health and economic impact of using high-dose influenza vaccine on respiratory and circulatory plus respiratory hospitalizations of older adults in Australia

Background

Standard dose influenza vaccine provides moderate protection from infection, but with lower effectiveness among the elderly. High dose and adjuvanted vaccines (HD-TIV and aTIV) were developed to address this. This study aims to estimate the incremental health and economic impact of using HD-TIV (high dose trivalent vaccine) instead of aTIV (adjuvanted trivalent vaccine) on respiratory and circulatory plus respiratory hospitalizations of older people (≥65 years) in Australia.

Methods

This is a modelling study comparing predicted hospitalization outcomes in people receiving HD-TIV or aTIV during an average influenza season in Australia. Hospitalization records of Australian adults ≥65 years of age from 01 April to 30 November during 15 influenza seasons (2002-2017 excluding 2009, which was a pandemic) were extracted from the Australian Institute of Health and Welfare [AIHW] and used to calculate hospitalisation rates during an average season. Relative vaccine effectiveness data for aTIV and HD-TIV were used to estimate morbidity burden related to influenza.

Results

Between 2002 and 2017, the average respiratory hospitalization rate among older people during influenza season (April-November) was 3,445/100,000 population-seasons, with an average cost of AU$ 7,175 per admission. The average circulatory plus respiratory hospitalization rate among older Australian people during that time was 10,393/100,000 population-seasons, with an average cost of AU$ 7829 per admission. For older Australians, HD-TIV may avert an additional 6,315-9,410 respiratory admissions each year, with an incremental healthcare cost saving of AU$ 15.9-38.2 million per year compared to aTIV. Similar results were also noted for circulatory plus respiratory hospitalizations.

Conclusions

From the modelled estimations, HD-TIV was associated with less economic burden and fewer respiratory, and circulatory plus respiratory hospitalizations than aTIV for older Australians.

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

With the progressive lengthening of the average age of the population, especially in some countries such as Italy, vaccination of the elderly is a fixed point on which most of the public health efforts are concentrating as epidemic infectious diseases, especially those of the winter, have a major impact on the progression of severe disease, hospitalization, and death. The protection of the elderly against acute infectious diseases should not only limit mortality but also have a positive impact on the fragility of these people in terms of less disability and fewer care needs. However, vaccination of the elderly population differs in efficacy and safety compared to that of other population categories since aging and the consequent loss of efficiency of the immune system lead to a reduction in the immunogenicity of vaccines without achieving a lasting antibody coverage. There are various strategies to avoid the failure of immunization by vaccines such as resorting to supplementary doses with adjuvant vaccines, increasing the dosage of the antigen used, or choosing to inoculate the serum relying on various routes of administration of the vaccine. Vaccination in the elderly is also an important factor in light of growing antibiotic resistance because it can indirectly contribute to combating antibiotic resistance, reducing theoretically the use of those agents. Furthermore, vaccination in old age reduces mortality from infectious diseases preventable with vaccines and reduces the same rate of resistance to antibiotics. Given the importance and complexity of the topic, in this review, we will deal with the main aspects of vaccination in the elderly and how it can influence mortality and healthcare costs, especially in those countries where population aging is more evident. Therefore, we conducted a systematic literature search in PubMed to identify all types of studies published up to 31 May 2023 that examined the association between vaccination and the elderly. Data extraction and quality assessment were conducted by two reviewers (PC and TC) who independently extracted the following data and assessed the quality of each study.

Older Adults Who Maintained a Regular Physical Exercise Routine before the Pandemic Show Better Immune Response to Vaccination for COVID-19

BACKGROUND

In this study, we aimed to investigate the specific-antibody response to the COVID-19 vaccination and the immunophenotyping of T cells in older adults who were engaged or not in an exercise training program before the pandemic.

METHODS

Ninety-three aged individuals (aged between 60 and 85 years) were separated into 3 groups: practitioners of physical exercise vaccinated with CoronaVac (PE-Co, n = 46), or vaccinated with ChadOx-1 (PE-Ch, n = 23), and non-practitioners vaccinated with ChadOx-1 (NPE-Ch, n = 24). Blood samples were collected before (pre) and 30 days after vaccination with the second vaccine dose.

RESULTS

Higher IgG levels and immunogenicity were found in the PE-Ch and NPE-Ch groups, whereas increased IgA levels were found only in the PE-Ch group post-vaccination. The PE-Co group showed a positive correlation between the IgA and IgG values, and lower IgG levels post-vaccination were associated with age. Significant alterations in the percentage of naive (CD28+CD57-), double-positive (CD28+CD57+), and senescent (CD28-CD57+) CD4+ T and CD8+ T cells were found post-vaccination, particularly in the PE-Ch group.

CONCLUSIONS

The volunteers vaccinated with the ChadOx-1 presented not only a better antibody response but also a significant modulation in the percentage of T cell profiles, mainly in the previously exercised group.

Factors associated with humoral immune response in older adults who received egg-free influenza vaccine

BACKGROUND

Immune responses to influenza vaccination tend to be lower among older, frequently vaccinated adults. Use of egg-free influenza vaccines is increasing, but limited data exist on factors associated with their immunogenicity in older adults.

METHODS

Community-dwelling older adults ≥ 56 years of age were enrolled in a prospective, observational study of immunogenicity of 2018-2019 influenza vaccine. Hemagglutination inhibition (HAI) antibody titers were measured pre-vaccination (Day 0) and four weeks after vaccination (Day 28) to calculate geometric mean titers, seropositivity (HAI titers ≥ 1:40), seroconversion (fourfold rise in HAI titer with post-vaccination titer ≥ 1:40) and geometric mean fold rise (GMFR). Linear regression models assessed the association of predictors of GMFR for each vaccine antigen.

RESULTS

Among 91 participants who received egg-free influenza vaccines, 84 (92.3 %) received quadrivalent recombinant influenza vaccine (RIV4, Flublok, Sanofi Pasteur), and 7 (7.7 %) received quadrivalent cell culture-based influenza vaccine (ccIIV4, Flucelvax, Seqirus). Pre-vaccination seropositivity was 52.8 % for A(H1N1), 94.5 % for A(H3N2), 61.5 % for B/Colorado and 48.4 % for B/Phuket. Seroconversion by antigen ranged from 16.5 % for A(H1N1) and B/Colorado to 37.4 % for A(H3N2); 40 participants failed to seroconvert to any antigen. Factors independently associated with higher GMFR in multivariable models included lower pre-vaccination HAI antibody titer for A(H1N1), B/Colorado and B/Phuket, and younger age for A(H1N1).

CONCLUSION

Overall pre-vaccination seropositivity was high and just over half of the cohort seroconverted to ≥ 1 vaccine antigen. Antibody responses were highest among participants with lower pre-vaccination titers. Among older adults with high pre-existing antibody titers, approaches to improve immune responses are needed.

IgD+ age-associated B cells are the progenitors of the main T-independent B cell response to infection that generates protective Ab and can be induced by an inactivated vaccine in the aged

Age-associated B cells (ABC) accumulate with age and are associated with autoimmunity and chronic infection. However, their contributions to acute infection in the aged and their developmental pathways are unclear. We find that the response against influenza A virus infection in aged mice is dominated by a Fas+ GL7- effector B cell population we call infection-induced ABC (iABC). Most iABC express IgM and include antibody-secreting cells in the spleen, lung, and bone marrow. We find that in response to influenza, IgD+ CD21- CD23- ABC are the precursors of iABC and become memory B cells. These IgD+ ABC develop in germ-free mice, so are independent of foreign antigen recognition. The response of ABC to influenza infection, resulting in iABC, is T cell independent and requires both extrinsic TLR7 and TLR9 signals. In response to influenza infection, IgD+ ABC can induce a faster recovery of weight and higher total anti-influenza IgG and IgM titers that can neutralize virus. Immunization with whole inactivated virus also generates iABC in aged mice. Thus, in unimmunized aged mice, whose other B and T cell responses have waned, IgD+ ABC are likely the naive B cells with the potential to become Ab-secreting cells and to provide protection from infection in the aged.

Alterations in high-dimensional T-cell profile and gene signature of immune aging in HIV-infected older adults without viremia

Alterations in the components of the immune system occur with aging. The introduction of combination antiretroviral therapy (ART) has dramatically improved life expectancy in human immunodeficiency virus (HIV) infected individuals by suppressing viral replication and increasing CD4+ T-cell counts. Immunosenescence-like changes, including the expansion of memory CD8+ T cells with senescent features, are reported in young HIV-infected individuals who do not have clinically detectable viremia on ART. However, it is less known whether HIV infection affects the immunosenescent status in older HIV-infected individuals. Here, we addressed this question in older HIV-infected, HIV-uninfected, and frail individuals (all groups age ≥65 years) by examining a set of aging-associated genes in peripheral blood mononuclear cells (PBMCs) as well as by analyzing subsets of CD4+ and CD8+ T cells in depth using high-dimensional CyTOF analysis. Older HIV-infected individuals had increased expression of aging-associated genes such as CX3CR1 in PBMCs which are related to IL-7 receptor low effector memory (IL-7Rαlow EM) CD8+ T cells, a cell population known to expand with age. The subsets of IL-7Rαlow EM CD8+ T cells expressing senescent, cytotoxic, and inflammatory molecules, including CD57, perforin, and CX3CR1, as well as memory CD4+ T cells expressing CD161 and CXCR3, molecules associated with replication-competent HIV-1 harboring cells, were increased in older HIV-infected individuals. Overall, older HIV-infected individuals without detectable viremia on ART had augmented levels of age-associated immune alterations in PBMCs, suggesting that HIV infection has a persistent impact on senescence in older HIV-infected individuals despite the clinically controlled viremia.

Geriatric Health Care During the COVID-19 Pandemic: Managing the Health Crisis

COVID-19 pandemic significantly threatens the health and well-being of older adults. Aging-related changes, including multimorbidity, weakened immunity and frailty, may make older people more susceptible to severe infection and place them at higher risk of morbidity and mortality from COVID-19. Various quarantine measures have been implemented to control the spread of COVID-19. Nevertheless, such social distancing has disrupted routine health care practices, such as accessibility of medical services and long-term continuous care services. The medical management of older adults with multimorbidity is significantly afflicted by COVID-19. Older persons with frailty or multiple chronic disease may poorly adapt to the altered health care system, having detrimental consequences on their physical and mental health. COVID-19 pandemic has posed great challenges to the health of older adults. We highlighted the difficulties and obstacles of older adults during this unprecedented time. Also, we provided potential strategies and recommendations for actions to mitigate the COVID-19 pandemic threats. Certain strategies like community primary health care, medication delivery and home care support are adopted by many health facilities and caregivers, whereas other services such as internet hospital and virtual medical care are promoted to be accessible in many regions. However, guidelines and policies based on high-quality data are still needed for better health promotion of older groups with increasing resilience during the COVID-19 pandemic.

Metabolomic and transcriptomic signatures of influenza vaccine response in healthy young and older adults

Seasonal influenza causes mild to severe respiratory infections and significant morbidity, especially in older adults. Transcriptomic analysis in populations across multiple flu seasons has provided insights into the molecular determinants of vaccine response. Still, the metabolic changes that underlie the immune response to influenza vaccination remain poorly characterized. We performed untargeted metabolomics to analyze plasma metabolites in a cohort of younger and older subjects before and after influenza vaccination to identify vaccine-induced molecular signatures. Metabolomic and transcriptomic data were combined to define networks of gene and metabolic signatures indicative of high and low antibody response in these individuals. We observed age-related differences in metabolic baselines and signatures of antibody response to influenza vaccination and the abundance of α-linolenic and linoleic acids, sterol esters, fatty-acylcarnitines, and triacylglycerol metabolism. We identified a metabolomic signature associated with age-dependent vaccine response, finding increased tryptophan and decreased polyunsaturated fatty acids (PUFAs) in young high responders (HRs), while fatty acid synthesis and cholesteryl esters accumulated in older HRs. Integrated metabolomic and transcriptomic analysis shows that depletion of PUFAs, which are building blocks for prostaglandins and other lipid immunomodulators, in young HR subjects at Day 28 is related to a robust immune response to influenza vaccination. Increased glycerophospholipid levels were associated with an inflammatory response in older HRs to flu vaccination. This multi-omics approach uncovered age-related molecular markers associated with influenza vaccine response and provides insight into vaccine-induced metabolic responses that may help guide development of more effective influenza vaccines.

Protein-Based Adjuvants for Vaccines as Immunomodulators of the Innate and Adaptive Immune Response: Current Knowledge, Challenges, and Future Opportunities

New-generation vaccines, formulated with subunits or nucleic acids, are less immunogenic than classical vaccines formulated with live-attenuated or inactivated pathogens. This difference has led to an intensified search for additional potent vaccine adjuvants that meet safety and efficacy criteria and confer long-term protection. This review provides an overview of protein-based adjuvants (PBAs) obtained from different organisms, including bacteria, mollusks, plants, and humans. Notably, despite structural differences, all PBAs show significant immunostimulatory properties, eliciting B-cell- and T-cell-mediated immune responses to administered antigens, providing advantages over many currently adopted adjuvant approaches. Furthermore, PBAs are natural biocompatible and biodegradable substances that induce minimal reactogenicity and toxicity and interact with innate immune receptors, enhancing their endocytosis and modulating subsequent adaptive immune responses. We propose that PBAs can contribute to the development of vaccines against complex pathogens, including intracellular pathogens such as Mycobacterium tuberculosis, those with complex life cycles such as Plasmodium falciparum, those that induce host immune dysfunction such as HIV, those that target immunocompromised individuals such as fungi, those with a latent disease phase such as Herpes, those that are antigenically variable such as SARS-CoV-2 and those that undergo continuous evolution, to reduce the likelihood of outbreaks.

Importance and value of adjuvanted influenza vaccine in the care of older adults from a European perspective - A systematic review of recently published literature on real-world data

BACKGROUND

There is an urgent need for improved influenza vaccines especially for older adults due to the presence of immunosenescence. It is therefore highly relevant to compare enhanced influenza vaccines with traditional influenza vaccines with respect to their effectiveness.

OBJECTIVE

To compare vaccine efficacy and effectiveness of adjuvanted influenza vaccines (aTIV/aQIV) vs. non-adjuvanted standard-dose (TIV/QIV) and high-dose (TIV-HD/QIV-HD) influenza vaccines regarding influenza-related outcomes in older adults, complementing findings from the European Centre for Disease Prevention and Control (ECDC)'s systematic review of enhanced seasonal influenza vaccines from February 2020.

METHODS

A systematic literature search was conducted in Embase and MEDLINE to identify randomised controlled trials, observational studies and systematic reviews, published since ECDC's systematic review (between 7 February 2020 and 6 September 2021). Included studies were appraised with either the Cochrane Risk of Bias tool, ROBINS-I or AMSTAR 2.

RESULTS

Eleven analyses from nine real-world evidence (RWE) studies comprising ∼53 million participants and assessing the relative vaccine effectiveness (rVE) of aTIV vs. TIV, QIV and/or TIV-HD in adults aged ≥65 years over the 2006/07-2008/09 and 2011/12-2019/20 influenza seasons were identified. Nine analyses found that aTIV was significantly more effective than TIV and QIV in reducing influenza-related outcomes by clinical setting and suspected influenza outbreaks (rVE ranging from 7.5% to 25.6% for aTIV vs. TIV and 7.1% to 36.3% for aTIV vs. QIV). Seven analyses found similar effectiveness of aTIV vs. TIV-HD in reducing influenza-related medical encounters, inpatient stays and hospitalisations/emergency room visits. In three analyses, aTIV was significantly more effective than TIV-HD in reducing influenza-related medical encounters and office visits (rVE ranging from 6.6% to 16.6%). Risk of bias of identified studies was moderate to high.

CONCLUSIONS

Our study suggests that both adjuvanted and high-dose vaccines are effective alternatives for vaccination programmes in older adults and preferable over conventional standard-dose vaccines.

Vaccine strain affects seroconversion after influenza vaccination in COPD patients and healthy older people

Though clinical guidelines recommend influenza vaccination for chronic obstructive pulmonary disease (COPD) patients and other high-risk populations, it is unclear whether current vaccination strategies induce optimal antibody responses. This study aimed to identify key variables associated with strain-specific antibody responses in COPD patients and healthy older people. 76 COPD and 72 healthy participants were recruited from two Australian centres and inoculated with influenza vaccine. Serum strain-specific antibody titres were measured pre- and post-inoculation. Seroconversion rate was the primary endpoint. Antibody responses varied between vaccine strains. The highest rates of seroconversion were seen with novel strains (36-55%), with lesser responses to strains included in the vaccine in more than one consecutive year (27-33%). Vaccine responses were similar in COPD patients and healthy participants. Vaccine strain, hypertension and latitude were independent predictors of seroconversion. Our findings reassure that influenza vaccination is equally immunogenic in COPD patients and healthy older people; however, there is room for improvement. There may be a need to personalise the yearly influenza vaccine, including consideration of pre-existing antibody titres, in order to target gaps in individual antibody repertoires and improve protection.

Influenza Vaccination Is Associated With Lower Incidental Asthma Risk in Patients With Atopic Dermatitis: A Nationwide Cohort Study

Background

Atopic march refers to the natural history of atopic dermatitis (AD) in infancy followed by subsequent allergic rhinitis and asthma in later life. Respiratory viruses interact with allergic sensitization to promote recurrent wheezing and the development of asthma. We aimed to evaluate whether influenza vaccination reduces asthma risk in people with AD.

Methods

This cohort study was conducted retrospectively from 2000 to 2013 by the National Health Insurance Research Database (NHIRD). Patients with newly diagnosed AD (International Classification of Diseases, Ninth Revision, Clinical Modification code 691) were enrolled as the AD cohort. We matched each vaccinated patient with one non-vaccinated patient according to age and sex. We observed each participant until their first asthma event, or the end of the study on December 31, 2013, whichever came first.

Results

Our analyses included 4,414 people with a mean age of 53 years. Of these, 43.8 were male. The incidence density of asthma was 12.6 per 1,000 person-years for vaccinated patients, and 15.1 per 1000 person-years for non-vaccinated patients. The adjusted hazard ratio (aHR) of asthma in the vaccinated cohort relative to the non-vaccinated cohort was 0.69 (95% CI = 0.55–0.87). Vaccinated patients had a lower cumulative incidence of asthma than unvaccinated patients. Vaccinated participants in all age and sex groups trended toward a lower risk of asthma. People will reduce more asthma risk when taking shots every year.

Conclusion

Influenza vaccination was associated with lower asthma risk in patients with AD.

Anti-SARS-CoV-2 Antibody Levels Measured by the AdviseDx SARS-CoV-2 Assay Are Concordant with Previously Available Serologic Assays but Are Not Fully Predictive of Sterilizing Immunity

With the availability of widespread SARS-CoV-2 vaccination, high-throughput quantitative anti-spike protein serological testing will likely become increasingly important. Here, we investigated the performance characteristics of the recently FDA-authorized semiquantitative anti-spike protein AdviseDx SARS-CoV-2 IgG II assay compared to the FDA-authorized anti-nucleocapsid protein Abbott Architect SARS-CoV-2 IgG, Roche Elecsys anti-SARS-CoV-2-S, EuroImmun anti-SARS-CoV-2 enzyme-linked immunosorbent assay (ELISA), and GenScript surrogate virus neutralization assays and examined the humoral response associated with vaccination, natural protection, and vaccine breakthrough infection. The AdviseDx assay had a clinical sensitivity at 14 days after symptom onset or 10 days after PCR detection of 95.6% (65/68; 95% confidence interval [CI], 87.8 to 98.8%), with two discrepant individuals seroconverting shortly thereafter. The AdviseDx assay demonstrated 100% positive percent agreement with the four other assays examined using the same symptom onset or PCR detection cutoffs. Using a recently available WHO international standard for anti-SARS-CoV-2 antibody, we provide assay unit conversion factors to international units for each of the assays examined. We performed a longitudinal survey of healthy vaccinated individuals, finding that median AdviseDx immunoglobulin levels peaked 7 weeks after first vaccine dose at approximately 4,000 IU/ml. Intriguingly, among the five assays examined, there was no significant difference in antigen binding level or neutralizing activity between two seropositive patients protected against SARS-CoV-2 infection in a previously described fishing vessel outbreak and five health care workers who experienced vaccine breakthrough of SARS-CoV-2 infection, all with variants of concern. These findings suggest that protection against SARS-CoV-2 infection cannot currently be predicted exclusively using in vitro antibody assays against wild-type SARS-CoV-2 spike. Further work is required to establish protective correlates for SARS-CoV-2 infection.

Influenza vaccine: progress in a vaccine that elicits a broad immune response

INTRODUCTION

The licensed seasonal influenza vaccines predominantly induce neutralizing antibodies against immunodominant hypervariable epitopes of viral surface proteins, with limited protection against antigenically distant influenza viruses. Strategies have been developed to improve vaccines' performance in terms of broadly reactive and long-lasting immune response induction.

AREAS COVERED

We have summarized the advancements in the development of cross-protective influenza vaccines and discussed the challenges in evaluating them in preclinical and clinical trials. Here, the literature regarding the current stage of development of universal influenza vaccine candidates was reviewed.

EXPERT OPINION

Although various strategies aim to redirect adaptive immune responses from variable immunodominant to immunosubdominant antigens, more conserved epitopes are being investigated. Approaches that improve antibody responses to conserved B cell epitopes have increased the protective efficacy of vaccines within a subtype or phylogenetic group of influenza viruses. Vaccines that elicit significant levels of T cells recognizing highly conserved viral epitopes possess a high cross-protective potential and may cover most circulating influenza viruses. However, the development of T cell-based universal influenza vaccines is challenging owing to the diversity of MHCs in the population, unpredictable degree of immunodominance, lack of adequate animal models, and difficulty in establishing T cell immunity in humans.

ABBREVIATIONS

cHA: chimeric HA; HBc: hepatitis B virus core protein; HA: hemagglutinin; HLA: human leucocyte antigen; IIV: inactivated influenza vaccine; KLH: keyhole limpet hemocyanin; LAH: long alpha helix; LAIV: live attenuated influenza vaccine; M2e: extracellular domain of matrix 2 protein; MHC: major histocompatibility complex; mRNA: messenger ribonucleic acid; NA: neuraminidase; NS1: non-structural protein 1; qNIV: quadrivalent nanoparticle influenza vaccine; T_RM: tissue-resident memory T cells; VE: vaccine effectiveness; VLP: virus-like particles; VSV: vesicular stomatitis virus.

A non-neutralizing antibody broadly protects against influenza virus infection by engaging effector cells

Hemagglutinin (HA) is the immunodominant protein of the influenza virus. We previously showed that mice injected with a monoglycosylated influenza A HA (HA_mg) produced cross-strain-reactive antibodies and were better protected than mice injected with a fully glycosylated HA (HA_fg) during lethal dose challenge. We employed a single B-cell screening platform to isolate the cross-protective monoclonal antibody (mAb) 651 from mice immunized with the HA_mg of A/Brisbane/59/2007 (H1N1) influenza virus (Bris/07). The mAb 651 recognized the head domain of a broad spectrum of HAs from groups 1 and 2 influenza A viruses and offered prophylactic and therapeutic efficacy against A/California/07/2009 (H1N1) (Cal/09) and Bris/07 infections in mice. The antibody did not possess neutralizing activity; however, antibody-dependent cellular cytotoxicity and antibody-dependent cellular phagocytosis mediated by natural killer cells and alveolar macrophages were important in the protective efficacy of mAb 651. Together, this study highlighted the significance of effector functions for non-neutralizing antibodies to exhibit protection against influenza virus infection.

The protective efficacy of antibodies is generally related to their neutralization potency. Here, we isolated a monoclonal antibody from mice injected with monoglycosylated hemagglutinin protein-based universal influenza vaccine, and demonstrated a head-domain recognizing, but non-neutralizing, monoclonal antibody carried prophylactic and therapeutic efficacy against a broad spectrum of influenza virus infections in vivo via effector functions.

Exosome therapeutics for COVID-19 and respiratory viruses

Respiratory viral diseases are a leading cause of mortality in humans. They have proven to drive pandemic risk due to their complex transmission factors and viral evolution. However, the slow production of effective antiviral drugs and vaccines allows for outbreaks of these diseases, emphasizing a critical need for refined antiviral therapeutics. The delivery of exosomes, a naturally secreted extracellular vesicle, yields therapeutic effects for a variety of diseases, including viral infection. Exosomes and viruses utilize similar endosomal sorting pathways and mechanisms, providing exosomes with the potential to serve as a therapeutic that can target, bind, and suppress cellular uptake of various viruses including the novel severe acute respiratory syndrome coronavirus 2. Here, we review the relationship between exosomes and respiratory viruses, describe potential exosome therapeutics for viral infections, and summarize progress toward clinical translation for lung-derived exosome therapeutics.

Age-Related Changes in Thymic Central Tolerance

Thymic epithelial cells (TECs) and hematopoietic antigen presenting cells (HAPCs) in the thymus microenvironment provide essential signals to self-reactive thymocytes that induce either negative selection or generation of regulatory T cells (Treg), both of which are required to establish and maintain central tolerance throughout life. HAPCs and TECs are comprised of multiple subsets that play distinct and overlapping roles in central tolerance. Changes that occur in the composition and function of TEC and HAPC subsets across the lifespan have potential consequences for central tolerance. In keeping with this possibility, there are age-associated changes in the cellular composition and function of T cells and Treg. This review summarizes changes in T cell and Treg function during the perinatal to adult transition and in the course of normal aging, and relates these changes to age-associated alterations in thymic HAPC and TEC subsets.

Differential Influence of Age on the Relationship between Genetic Mismatch and A(H1N1)pdm09 Vaccine Effectiveness

Assessment of influenza vaccine effectiveness (VE) and identification of relevant influencing factors are the current priorities for optimizing vaccines to reduce the impacts of influenza. To date, how the difference between epidemic strains and vaccine strains at genetic scale affects age-specific vaccine performance remains ambiguous. This study investigated the association between genetic mismatch on hemagglutinin and neuraminidase genes and A(H1N1)pdm09 VE in different age groups with a novel computational approach. We found significant linear relationships between VE and genetic mismatch in children, young adults, and middle-aged adults. In the children’s group, each 3-key amino acid mutation was associated with an average of 10% decrease in vaccine effectiveness in a given epidemic season, and genetic mismatch exerted no influence on VE for the elderly group. We demonstrated that present vaccines were most effective for children, while protection for the elderly was reduced and indifferent to vaccine component updates. Modeling such relationships is practical to inform timely evaluation of VE in different groups of populations during mass vaccination and may inform age-specific vaccination regimens.

Transcriptional and Immunologic Correlates of Response to Pandemic Influenza Vaccine in Aviremic, HIV-Infected Children

People living with HIV (PWH) often exhibit poor responses to influenza vaccination despite effective combination anti-retroviral (ART) mediated viral suppression. There exists a paucity of data in identifying immune correlates of influenza vaccine response in context of HIV infection that would be useful in improving its efficacy in PWH, especially in younger individuals. Transcriptomic data were obtained by microarray from whole blood isolated from aviremic pediatric and adolescent HIV-infected individuals (4-25 yrs) given two doses of Novartis/H1N1 09 vaccine during the pandemic H1N1 influenza outbreak. Supervised clustering and gene set enrichment identified contrasts between individuals exhibiting high and low antibody responses to vaccination. High responders exhibited hemagglutination inhibition antibody titers >1:40 post-first dose and 4-fold increase over baseline. Baseline molecular profiles indicated increased gene expression in metabolic stress pathways in low responders compared to high responders. Inflammation-related and interferon-inducible gene expression pathways were higher in low responders 3 wks post-vaccination. The broad age range and developmental stage of participants in this study prompted additional analysis by age group (e.g. <13yrs and ≥13yrs). This analysis revealed differential enrichment of gene pathways before and after vaccination in the two age groups. Notably, CXCR5, a homing marker expressed on T follicular helper (Tfh) cells, was enriched in high responders (>13yrs) following vaccination which was accompanied by peripheral Tfh expansion. Our results comprise a valuable resource of immune correlates of vaccine response to pandemic influenza in HIV infected children that may be used to identify favorable targets for improved vaccine design in different age groups.

Co-expression network analysis identifies innate immune signatures for Albizia julibrissin saponin active fraction-adjuvanted avian influenza vaccine

Albizia julibrissin saponin active fraction (AJSAF) is a promising adjuvant candidate, but its innate immune response mechanisms remain unclear. Here, the quadriceps muscles from the mice injected intramuscularly with AJSAF alone or in combination with ovalbumin and avian influenza vaccine (rL-H5) were subjected to gene microarray. Antigen- and AJSAF-related modules with intramodular hub genes were identified and functionally analyzed using weighted gene co-expression network analysis (WGCNA) and gene set enrichment analysis (GSEA). AJSAF induced early innate immune responses at the injection site, characterized by cytokine production and neutrophil recruitment. AJSAF mainly elicited the expression of "Th1 immune response" and "Neutrophils" genes such as CCL2, CXCL1, CXCL5, IL-1β, IL-6, IL-33, S100A8, and S100A9, whereas these two gene sets were negatively enriched for rL-H5. AJSAF-specific long noncoding RNAs MIRT1 and MIRT2 could function as inflammatory mediators, whereas function unknown TINCR was co-expressed with immune response genes including CCL2, CCL4, CCL7, CSF3, CXCL5, IL-33, S100A8, and S100A9. Finally, the innate immune molecular mechanisms of adjuvant action of AJSAF and the potential signatures were proposed. These findings expanded the current knowledge on the mechanisms of action of saponin-based adjuvants.

Effectiveness of inactivated influenza vaccine in autoimmune rheumatic diseases treated with disease-modifying anti-rheumatic drugs

OBJECTIVES

The effectiveness of inactivated influenza vaccine in people with autoimmune rheumatic disease (AIRDs) is not known. We investigated whether the influenza vaccine is effective in preventing respiratory morbidity, mortality and all-cause mortality in AIRD patients.

METHODS

Adults with AIRDs treated with DMARDs prior to 1 September of each year between 2006 and 2009, and 2010 and 2015 were identified from the Clinical Practice Research Datalink. Exposure and outcome data were extracted. Data from multiple seasons were pooled. Propensity score (PS) for vaccination was calculated. Cox-proportional hazard ratios (HRs) and 95% CIs were calculated, and were (i) adjusted, (ii) matched for PS for vaccination.

RESULTS

Data for 30 788 AIRD patients (65.7% female, 75.5% with RA, 61.1% prescribed MTX) contributing 125 034 influenza cycles were included. Vaccination reduced risk of influenza-like illness [adjusted HR (aHR) 0.70], hospitalization for pneumonia (aHR 0.61) and chronic obstructive pulmonary disease exacerbations (aHR 0.67), and death due to pneumonia (aHR 0.56) on PS-adjusted analysis in the influenza active periods (IAPs). The associations were of similar magnitude and remained statistically significant on PS-matched analysis except for protection from influenza-like illness, which became non-significant. Sub-analysis restricted to pre-IAP, IAP and post-IAP did not yield evidence of residual confounding on influenza-like illness and death due to pneumonia. Vaccination reduced risk of all-cause mortality, although IAP-restricted analysis demonstrated residual confounding for this outcome.

CONCLUSION

Influenza vaccine associates with reduced risk of respiratory morbidity and mortality in people with AIRDs. These findings call for active promotion of seasonal influenza vaccination in immunosuppressed people with AIRDs by healthcare professionals.

The impact of physical frailty on the response to inactivated influenza vaccine in older adults

Physical frailty's impact on hemagglutination inhibition antibody titers (HAI) and peripheral blood mononuclear cell (PBMC) transcriptional responses after influenza vaccination is unclear. Physical frailty was assessed using the 5-item Fried frailty phenotype in 168 community- and assisted-living adults ≥55 years of age during an observational study. Blood was drawn before, 3, 7, and 28 days post-vaccination with the 2017-2018 inactivated influenza vaccine. HAI response to the A/H1N1 strain was measured at Days 0 and 28 using seropositivity, seroconversion, log2 HAI titers, and fold-rise in log2 HAI titers. RNA sequencing of PBMCs from Days 0, 3 and 7 was measured in 28 participants and compared using pathway analyses. Frailty was not significantly associated with any HAI outcome in multivariable models. Compared with non-frail participants, frail participants expressed decreased cell proliferation, metabolism, antibody production, and interferon signaling genes. Conversely, frail participants showed elevated gene expression in IL-8 signaling, T-cell exhaustion, and oxidative stress pathways compared with non-frail participants. These results suggest that reduced effectiveness of influenza vaccine among older, frail individuals may be attributed to immunosenescence-related changes in PBMCs that are not reflected in antibody levels.

How age and infection history shape the antigen-specific CD8+ T-cell repertoire: Implications for vaccination strategies in older adults

Older adults often show signs of impaired CD8⁺ T‐cell immunity, reflected by weaker responses against new infections and vaccinations, and decreased protection against reinfection. This immune impairment is in part thought to be the consequence of a decrease in both T‐cell numbers and repertoire diversity. If this is indeed the case, a strategy to prevent infectious diseases in older adults could be the induction of protective memory responses through vaccination at a younger age. However, this requires that the induced immune responses are maintained until old age. It is therefore important to obtain insights into the long‐term maintenance of the antigen‐specific T‐cell repertoire. Here, we review the literature on the maintenance of antigen‐experienced CD8⁺ T‐cell repertoires against acute and chronic infections. We describe the complex interactions that play a role in shaping the memory T‐cell repertoire, and the effects of age, infection history, and T‐cell avidity. We discuss the implications of these findings for the development of new vaccination strategies to protect older adults.

Coronavirus disease-2019: A tocsin to our aging, unfit, corpulent, and immunodeficient society

Acute and chronic respiratory illnesses cause widespread morbidity and mortality, and this class of illness now includes the novel coronavirus severe acute respiratory syndrome that is causing coronavirus disease-2019 (COVID-19). The world is experiencing a major demographic shift toward an older, obese, and physically inactive populace. Risk factor assessments based on pandemic data indicate that those at higher risk for severe illness from COVID-19 include older males, and people of all ages with obesity and related comorbidities such as hypertension and type 2 diabetes. Aging in and of itself leads to negative changes in innate and adaptive immunity, a process termed immunosenescence. Obesity causes systemic inflammation and adversely impacts immune function and host defense in a way that patterns immunosenescence. Two primary prevention strategies to reduce the risk for COVID-19 at both the community and individual levels include mitigation activities and the adoption of lifestyle practices consistent with good immune health. Animal and human studies support the idea that, in contrast to high exercise workloads, regular moderate-intensity physical activity improves immunosurveillance against pathogens and reduces morbidity and mortality from viral infection and respiratory illnesses including the common cold, pneumonia, and influenza. The odds are high that infectious disease pandemics spawned by novel pathogens will continue to inflict morbidity and mortality as the world's population becomes older and more obese. COVID-19 is indeed a wake-up call, a tocsin, to the world that primary prevention countermeasures focused on health behaviors and hygiene demand our full attention and support.

Age-related factors that affect B cell responses to vaccination in mice and humans

Aging significantly changes the ability to respond to vaccinations and infections. In this review, we summarize published results on age-related changes in response to infection with the influenza virus and on the factors known to increase influenza risk infection leading to organ failure and death. We also summarize how aging affects the response to the influenza vaccine with a special focus on B cells, which have been shown to be less responsive in the elderly. We show the cellular and molecular mechanisms contributing to the dysfunctional immune response of the elderly to the vaccine against influenza. These include a defective interaction of helper T cells (CD4+) with B cells in germinal centers, changes in the microenvironment, and the generation of immune cells with a senescence-associated phenotype. Finally, we discuss the effects of aging on metabolic pathways and we show how metabolic complications associated with aging lead to immune dysfunction.

Pandemic Influenza Vaccines: What did We Learn from the 2009 Pandemic and are We Better Prepared Now?

In 2009, a novel A(H1N1) influenza virus emerged with rapid human-to-human spread and caused the first pandemic of the 21st century. Although this pandemic was considered mild compared to the previous pandemics of the 20^th century, there was still extensive disease and death. This virus replaced the previous A(H1N1) and continues to circulate today as a seasonal virus. It is well established that vaccines are the most effective method to alleviate the mortality and morbidity associated with influenza virus infections, but the 2009 A(H1N1) influenza pandemic, like all significant infectious disease outbreaks, presented its own unique set of problems with vaccine supply and demand. This manuscript describes the issues that confronted governments, international agencies and industries in developing a well-matched vaccine in 2009, and identifies the key improvements and remaining challenges facing the world as the next influenza pandemic inevitably approaches.

Multi-Epitope Peptide-Based and Vaccinia-Based Universal Influenza Vaccine Candidates Subjected to Clinical Trials

In light of the limited protection conferred by current influenza vaccines, immunisation using universal influenza vaccines has been proposed for protection against all or most influenza sub-types. The fundamental principle of universal influenza vaccines is based on conserved antigens found in most influenza strains, such as matrix 2, nucleocapsid, matrix 1 and stem of hemagglutinin proteins. These antigens trigger cross-protective immunity against different influenza strains. Many researchers have attempted to produce the conserved epitopes of these antigens in the form of peptides in the hope of generating universal influenza vaccine candidates that can broadly induce cross-reactive protection against influenza viral infections. However, peptide vaccines are poorly immunogenic when applied individually owing to their small molecular sizes. Hence, strategies, such as combining peptides as multi-epitope vaccines or presenting peptides on vaccinia virus particles, are employed. This review discusses the clinical and laboratory findings of several multi-epitope peptide vaccine candidates and vaccinia-based peptide vaccines. The majority of these vaccine candidates have reached the clinical trial phase. The findings in this study will indeed shed light on the applicability of universal influenza vaccines to prevent seasonal and pandemic influenza outbreaks in the near future.

Immunogenicity of influenza vaccine in elderly people: a systematic review and meta-analysis of randomized controlled trials, and its association with real-world effectiveness

Background: Older people (≥60 years old) are particularly vulnerable to influenza virus infection, and vaccine is effective in reducing the disease burden in this population. However, it remains obscure whether their antibody response is lower than those of younger adults (18–60 years old). Thus, this meta-analysis was performed to compare the immunogenicity of influenza vaccines and understand their association with real-world vaccine effectiveness (VE) between these two age groups.

Methods: A systematic literature search was conducted to identify relevant studies from Jan 01, 2008 to Nov 10, 2018. These are randomized controlled trials that included older adult samples, which assessed the immunogenicity of inactivated quadrivalent influenza vaccines produced in embryonated eggs. We excluded the studies focused only in children or adults. The outcomes were seroprotecton rate (SPR) and seroconversion rate (SCR).

Results: Six studies were eventually included in the present meta-analysis (7,976 participants). For the SPR, the pooled risk ratio (RR) was 0.92 (95% CI: 0.90–0.94, I² = 66%, P < .0001) for A/H1N1 and 0.94 (95% CI: 0.90–0.98, I² = 91%, P = .002) for B/Victoria, and the antibody responses of A/H3N2 and B/Yamagata were similar in the two age groups. For the SCR, the pooled RR was 0.85 (95% CI: 0.76–0.94, I² = 93%, P = .003), 0.77 (95% CI: 0.66–0.91, I² = 94%, P = .002), and 0.83 (95% CI: 0.71–0.96, I² = 94%, P = .02) for A/H1N1, B/Victoria and B/Yamagata, respectively, and the antibody responses of A/H3N2 were similar in the two groups. Some variations were found in the antibody responses across virus types and subtypes after influenza vaccination.

Conclusion: The SPR and SCR of older adults were lower than those in younger adults for A/H1N1 and B/Victoria, while the two age groups had similar antibody responses for A/H3N2. The antibody responses to vaccines were not significantly associated with real-world VE, indicating that antibody response might not fully reflect the vaccine effectiveness of A/H3N2.

Immune Imprinting in the Influenza Ferret Model

The initial exposure to influenza virus usually occurs during childhood. This imprinting has long-lasting effects on the immune responses to subsequent infections and vaccinations. Animal models that are used to investigate influenza pathogenesis and vaccination do recapitulate the pre-immune history in the human population. The establishment of influenza pre-immune ferret models is necessary for understanding infection and transmission and for designing efficacious vaccines.

Understanding the Heterogeneous Population of Age-Associated B Cells and Their Contributions to Autoimmunity and Immune Response to Pathogens

In humans and mice, susceptibility to infections and autoimmunity increases with age due to age-associated changes in innate and adaptive immune responses. Aged innate cells are also less active, leading to decreased naive T- and B-cell responses. Aging innate cells contribute to an overall heightened inflammatory environment. Naive T and B cells undergo cell-intrinsic age-related changes that result in reduced effector and memory responses. However, previously established B- and T-cell memory responses persist with age. One dramatic change is the appearance of a newly recognized population of age-associated B cells (ABCs) that has a unique cluster of differentiation (CD)21-CD23- phenotype. Here, we discuss the discovery and origins of the naive phenotype immunoglobulin (Ig)D+ versus activated CD11c+T-bet+ ABCs, with a focus on protective and pathogenic properties. In humans and mice, antigen-experienced CD11c+T-bet+ ABCs increase with autoimmunity and appear in response to bacterial and viral infections. However, our analyses indicate that CD21-CD23- ABCs include a resting, naive, progenitor ABC population that expresses IgD. Similar to generation of CD11c+T-bet+ ABCs, naive ABC response to pathogens depends on toll-like receptor stimulation, making this a key feature of ABC activation. Here, we put forward a potential developmental map of distinct subsets from putative naive ABCs. We suggest that defining signals that can harness the naive ABC response may contribute to protection against pathogens in the elderly. CD11c+T-bet+ ABCs may be useful targets for therapeutic strategies to counter autoimmunity.

Aging and influenza vaccine-induced immunity

Immunosenescence is defined as the progressive deterioration of the immune system with aging. Immunosenescence stifles the generation of protective B and T cell-mediated adaptive immunity in response to various pathogens, resulting in increased disease susceptibility and severity in the elderly population. In particular, immunosenescence has major impacts on the phenotype, function, and receptor repertoire of B and T cells in the elderly, hindering protective responses induced by seasonal influenza virus vaccination. In order to overcome the detrimental impacts of immunosenescence on protective immunity to influenza viruses, we review our current understanding of the effects of aging on adaptive immune responses to influenza and discuss current and future avenues of vaccine research for eliciting more potent anti-influenza immunity in the elderly.

A Double-Blind, Randomized Trial of High-Dose vs Standard-Dose Influenza Vaccine in Adult Solid-Organ Transplant Recipients

Background

The annual standard-dose (SD) influenza vaccine has suboptimal immunogenicity in solid organ transplant recipients (SOTRs). Influenza vaccine that contains higher doses of antigens may lead to greater immunogenicity in this population.

Methods

We conducted a randomized, double-blind trial to compare the safety and immunogenicity of the 2016-2017 high-dose (HD; FluzoneHD, Sanofi) vs SD (Fluviral, GSK) influenza vaccine in adult SOTRs. Preimmunization and 4-week postimmunization sera underwent strain-specific hemagglutination inhibition assay.

Results

We enrolled 172 patients who received study vaccine, and 161 (84 HD; 77 SD) were eligible for analysis. Seroconversion to at least 1 of 3 vaccine antigens was present in 78.6% vs 55.8% in HD vs SD vaccine groups (P < .001), respectively. Seroconversions to A/ H1N1, A/H3N2, and B strains were 40.5% vs 20.5%, 57.1% vs 32.5%, and 58.3% vs 41.6% in HD vs SD vaccine groups (P = .006, P = .002, P = .028, respectively). Post-immunization geometric mean titers of A/H1N1, A/H3N2, and B strains were significantly higher in the HD group (P = .007, P = .002, P = .033). Independent factors associated with seroconversion to at least 1 vaccine strain were the use of HD vaccine (odds ratio [OR], 3.23; 95% confidence interval [CI], 1.56-6.67) and use of mycophenolate doses <2 g daily (OR, 2.76; 95% CI, 1.12-6.76).

Conclusions

HD vaccine demonstrated significantly better immunogenicity than SD vaccine in adult transplant recipients and may be the preferred influenza vaccine for this population.

Clinical Trials Registration

NCT03139565.

Transcriptomic analysis of human IL-7 receptor alpha low and high effector memory CD8+ T cells reveals an age-associated signature linked to influenza vaccine response in older adults

Here, we investigated the relationship of the age‐associated expansion of IL‐7 receptor alpha low (IL‐7Rα^low) effector memory (EM) CD8⁺ T cells with the global transcriptomic profile of peripheral blood cells in humans. We found 231 aging signature genes of IL‐7Rα^low EM CD8⁺ T cells that corresponded to 15% of the age‐associated genes (231/1,497) reported by a meta‐analysis study on human peripheral whole blood from approximately 15,000 individuals, having high correlation with chronological age. These aging signature genes were the target genes of several transcription factors including MYC, SATB1, and BATF, which also belonged to the 231 genes, supporting the upstream regulatory role of these transcription factors in altering the gene expression profile of peripheral blood cells with aging. We validated the differential expression of these transcription factors between IL‐7Rα^low and ^high EM CD8⁺ T cells as well as in peripheral blood mononuclear cells (PBMCs) of young and older adults. Finally, we found a significant association with influenza vaccine responses in older adults, suggesting the possible biological significance of the aging signature genes of IL‐7Rα^low EM CD8⁺ T cells. The results of our study support the relationship of the expansion of IL‐7Rα^low EM CD8⁺ T cells with the age‐associated changes in the gene expression profile of peripheral blood cells and its possible biological implications.

Public Health-Driven Research and Innovation for Next-Generation Influenza Vaccines, European Union

Influenza virus infections are a major public health threat. Vaccination is available, but unpredictable antigenic changes in circulating strains require annual modification of seasonal influenza vaccines. Vaccine effectiveness has proven limited, particularly in certain groups, such as the elderly. Moreover, preparedness for upcoming pandemics is challenging because we can predict neither the strain that will cause the next pandemic nor the severity of the pandemic. The European Union fosters research and innovation to develop novel vaccines that evoke broadly protective and long-lasting immune responses against both seasonal and pandemic influenza, underpinned by a political commitment to global public health.

EXamining the knowledge, Attitudes and experiences of Canadian seniors Towards influenza (the EXACT survey)

Background

Older adults are at high risk for influenza-related complications including worsening frailty and function. We surveyed older Canadians to explore the impact of influenza and determine how influenza knowledge influences vaccination decision-making.

Methods

We disseminated an online survey through a national polling panel. The survey included questions about the respondents’ influenza vaccination practices and knowledge about influenza. Using validated measures, they reported their frailty and functional status prior to the 2016/17 influenza season, during illness (if applicable), and following the season. Regression analyses were used to examine predictors of poor functional outcomes.

Results

Five thousand and fourteen adults aged 65 and older completed the survey; mean age was 71.3 ± 5.17 years, 42.6% had one or more chronic conditions, 7.8% were vulnerable and 1.8% were frail. 67.9% reported receiving last season’s influenza vaccine. Those who rarely/never receive the influenza vaccine were significantly less likely to correctly answer questions about influenza’s impact than those who receive the vaccine more consistently. Of the 1035 (21.5%) who reported experiencing influenza or influenza-like illness last season, 40% indicated a recovery longer than 2 weeks, and one-fifth had health and function declines during this time. Additionally, 3.1% of those afflicted “never fully recovered”. Older age, significant trouble with memory and having influenza/ILI were among the independent predictors of persistent declines in health and function.

Conclusions

Given that frailty and function are important considerations for older adults’ well-being and independence, healthcare decision-makers must understand the potential for significant temporary and long-term impacts of influenza to make informed vaccine-related policies and recommendations.

Immunogenicity and safety of a quadrivalent plant-derived virus like particle influenza vaccine candidate-Two randomized Phase II clinical trials in 18 to 49 and ≥50 years old adults

Background

New influenza vaccines eliciting more effective protection are needed, particularly for the elderly who paid a large and disproportional toll of hospitalization and dead during seasonal influenza epidemics. Low (≤15 μg/strain) doses of a new plant-derived virus-like-particle (VLP) vaccine candidate have been shown to induce humoral and cellular responses against both homologous and heterologous strains in healthy adults 18–64 years of age. The two clinical trials reported here addressed the safety and immunogenicity of higher doses (≥15 μg/strain) of quadrivalent VLP candidate vaccine on 18–49 years old and ≥50 years old subjects. We also investigated the impact of alum on the immunogenicity induced by lower doses of the vaccine candidate.

Method

In the first Phase II trial reported here (NCT02233816), 18–49 year old subjects received 15, 30 or 60 μg/strain of a hemagglutinin-bearing quadrivalent virus-like particle (QVLP) vaccine or placebo. In the second trial (NCT02236052), ≥50 years old subjects received QVLP as above or placebo with additional groups receiving 7.5 or 15 μg/strain with alum. Along with safety recording, the humoral and cell-mediated immune responses were analyzed.

Results

Local and systemic side-effects were similar to those reported previously. The QVLP vaccine induced significant homologous and heterologous antibody responses at the two higher doses, the addition of alum having little-to-no effect. Serologic outcomes tended to be lower in ≥50 years old subjects previously vaccinated. The candidate vaccine also consistently elicited both homologous and heterologous antigen-specific CD4⁺ T cells characterized by their production of interferon-gamma (IFN-γ), interleukine-2 (IL-2) and/or tumor-necrosis factor alpha (TNF-α) upon ex vivo antigenic restimulation.

Conclusion

Overall, the 30 μg dose produced the most consistent humoral and cellular responses in both 18–49 and ≥50 years old subjects, strongly supporting the clinical development of this candidate vaccine. That particular dose was chosen to test in the ongoing Phase III clinical trial.

Influence of aging on germinal centre reaction and antibody response to inactivated influenza virus antigens in mice: sex-based differences

The study examined sex-specificities in age-related changes in BALB/c mice IgG antibody responses to immunisation with trivalent inactivated split-virus influenza bulk. Aging diminished the total serum IgG antibody responses to H1N1 and H3N2 and B influenza virus antigens in mice of both sexes, but they remained greater in aged females. This sex difference in aged mice correlated with the greater post-immunisation increase in the frequency of spleen germinal centre (GC) B cells and more favourable T follicular regulatory (Tfr)/GC B cell ratio, as Tfr cells are suggested to control antibody production through suppression of glycolysis. The greater post-immunisation GC B cell response in aged females compared with males correlated with the greater proliferation of B cells and CD4+ cells in splenocyte cultures from aged females restimulated with inactivated split-virus influenza from the bulk. To support the greater post-immunisation increase in the frequency GC B cell in aged females was more favourable Tfr/T follicular helper (Tfh) cell ratio. Additionally, compared with aged males, in age-matched females the greater avidity of serum IgG antibodies was found. However, in aged females IgG2a/IgG1 antibody ratio, reflecting spleen Th1/Th2 cytokine balance, was shifted towards IgG1 when compared with age-matched male mice. This shift was ascribed to a more prominent decline in the titres of functionally important IgG2a antibodies in females with aging. The study suggest that biological sex should be considered as a variable in designing strategies to manipulate with immune outcome of immunisation in aged animals, and possibly, at very long distance, humans.

A clinically meaningful metric of immune age derived from high-dimensional longitudinal monitoring

Immune responses generally decline with age. However, the dynamics of this process at the individual level have not been characterized, hindering quantification of an individual's immune age. Here, we use multiple 'omics' technologies to capture population- and individual-level changes in the human immune system of 135 healthy adult individuals of different ages sampled longitudinally over a nine-year period. We observed high inter-individual variability in the rates of change of cellular frequencies that was dictated by their baseline values, allowing identification of steady-state levels toward which a cell subset converged and the ordered convergence of multiple cell subsets toward an older adult homeostasis. These data form a high-dimensional trajectory of immune aging (IMM-AGE) that describes a person's immune status better than chronological age. We show that the IMM-AGE score predicted all-cause mortality beyond well-established risk factors in the Framingham Heart Study, establishing its potential use in clinics for identification of patients at risk.

Immunogenicity of high-dose trivalent inactivated influenza vaccine: a systematic review and meta-analysis

INTRODUCTION

High-dose trivalent, inactivated, split-virus influenza vaccine (IIV3-HD) has been available in the US since 2009 for adults aged ≥ 65 years. To better understand how IIV3-HD provides improved protection against influenza, we systematically reviewed clinical studies comparing immune responses to IIV3-HD and standard-dose trivalent vaccine (IIV3-SD).

AREAS COVERED

The primary objective was to determine the relative hemagglutination inhibition (HAI) antibody response of IIV3-HD vs. IIV3-SD in adults aged ≥ 65 years. Based on seven randomized studies including more than 18,500 adults aged ≥ 65 years, combined HAI geometric mean titer (GMT) ratios (95% confidence interval) approximately 1 month post-vaccination were 1.74 (1.65-1.83) for influenza A/H1N1, 1.84 (1.73-1.95) for influenza A/H3N2, and 1.47 (1.36-1.58) for influenza B. HAI GMT ratios in these studies were similar irrespective of sex, older age (≥ 75 years), frailty, and underlying conditions. Trends were similar for A/H3N2 neutralization and anti-neuraminidase antibody titers. In immunocompromised individuals, HAI GMT ratios were mostly > 1.

EXPERT OPINION

In agreement with its improved efficacy and effectiveness, IIV3-HD is consistently more immunogenic than IIV3-SD in adults aged ≥ 65 years. IIV3-HD also appears more immunogenic in immunocompromised individuals.

Influenza Vaccination and Incident Tuberculosis among Elderly Persons, Taiwan1

Experimental studies have demonstrated that influenza vaccination may protect against tuberculosis (TB) through a Th17 response. This nationwide cohort study aimed to evaluate the association of influenza vaccination with incident TB among elderly persons in Taiwan. This 2005–2012 study included 99,982 elderly persons (64,290 vaccinated and 35,692 unvaccinated) from the Taiwan National Health Insurance Research Database. During the 738,367 person-years of follow-up, 1,141 (1.14%) persons had incident TB. The cumulative incidences of TB were 145.2 cases/100,000 person-years among vaccinated elderly persons and 175.5 cases/100,000 person-years among unvaccinated elderly persons (p = 0.002). The time-dependent Cox proportional hazards model revealed that influenza vaccination was an independent protective factor for incident TB. Our results suggest that influenza vaccination is associated with a lower risk of incident TB among elderly persons in Taiwan. Further investigation of biologic mechanisms is warranted.

Canadian older adults' perceptions of effectiveness and value of regular and high-dose influenza vaccines

Influenza vaccination is an important public health intervention for older adults, yet vaccination rates remain suboptimal. We conducted an online survey of Canadians ≥ 65 years to explore satisfaction with publicly-funded standard-dose influenza vaccines, and perceptions of the need for a more effective product. They were provided with information about currently approved influenza vaccines, and were asked about their preferences should all formulations be available for free, and should the recently approved high-dose (HD) vaccine for seniors be available at a cost. From March to April 2017, 5014 seniors completed the survey; mean age was 71.3 ± 5.17 years, 50% were female, and 42.6% had one or more chronic conditions. 3403 (67.9%) had been vaccinated against influenza in the 2016/17 season. Of all respondents, 3460 (69%) were satisfied with the standard-dose influenza vaccines, yet 3067 (61.1%) thought that a more effective vaccine was/may be needed. If HD was only available at a cost, 1426 (28.4%) respondents would consider it, of whom 62.9% would pay $20 or less. If all vaccines were free next season, 1914 (38.2%) would opt for HD (including 12.2% of those who previously rejected influenza vaccines), 856 (17.1%) would choose adjuvanted vaccine, and 558 (11.1%) standard-dose vaccine. 843 (16.8%) of respondents were against vaccines, 451 (9.0%) had no preference and 392 (7.8%) were uncertain. Making this product available through publicly funded programs may be a strategy to increase immunization rates in this population.

Strategies to maximize influenza vaccine impact in older adults

Older adults are disproportionately affected by influenza morbidity and mortality. In most high income countries, influenza vaccine policies target persons age ≥65 years for influenza vaccination. Many low-resource settings do not utilize seasonal influenza vaccination. Barriers to influenza prevention among older adults around the globe are multiple and some vary between high- and low-resource settings. To maximize influenza prevention in the older adult population, gaps in influenza vaccination coverage and improvements in vaccine efficacy are needed. The focus of this article is on the data for currently available vaccine strategies to maximize influenza vaccine impact, with a focus on high-resource settings. We also discuss novel influenza vaccine strategies needed for older adults worldwide.

Moderate influenza vaccine effectiveness against influenza A(H1N1)pdm09 virus and low effectiveness against A(H3N2) virus among older adults during 2013-2014 influenza season in Beijing, China

BACKGROUND

Since 2007, trivalent inactivated influenza vaccine has been provided free-of-charge to older adults aged ≥60 years in Beijing, China, but the data regarding influenza vaccine effectiveness (VE) among these people are very limited so far. We sought to estimate influenza VE against medically-attended laboratory-confirmed influenza illness among older adults during the 2013-2014 season.

METHODS

The influenza-like illness (ILI) patients aged 60 years and older who participated in the influenza virological surveillance of Beijing during 2013-2014 influenza season were recruited in this study. A test-negative design was employed to estimate influenza VE among older adults by using logistic regression models. VE was estimated using logistic regression, adjusted for sex, age, interval (days) between illness onset and specimen collection, and week of illness onset.

RESULTS

Between 1 November, 2013 and 30 April, 2014, a total of 487 elderly ILI patients were enrolled in the study, including 133 influenza-positive cases (of whom 6.8% were vaccinated) and 354 influenza-negative controls (of whom 10.2% were vaccinated). Among 133 influenza-positive cases, 51 tested positive for A(H1N1)pdm09 virus, 22 positive for A(H3N2) virus, 52 tested positive for B/Yamagata-lineage virus, 2 positive for B/Victoria-lineage virus, 1 positive for both A(H1N1)pdm09 and A(H3N2) viruses, and 5 tested positive for viruses of unknown subtype or lineage. The adjusted overall VE was estimated as 32% (95% CI:-48-69), with 59% (95% CI: -79-90) against A(H1N1)pdm09, 22% (95% CI: -253-83) against A(H3N2) and -20% (95% CI: -239-58) against B/Yamagata-lineage viruses.

CONCLUSIONS

These results suggested a modest protective effect of the 2013-2014 influenza vaccine among older adults in Beijing which was not statistically significant, with higher VE against the A(H1N1)pdm09 viruses compared to A(H3N2) and B viruses.

The establishment of surrogates and correlates of protection: Useful tools for the licensure of effective influenza vaccines?

The search for a test that can predict vaccine efficacy is an important part of any vaccine development program. Although regulators hesitate to acknowledge any test as a true ‘correlate of protection’, there are many precedents for defining ‘surrogate’ assays. Surrogates can be powerful tools for vaccine optimization, licensure, comparisons between products and development of improved products. When such tests achieve ‘reference’ status however, they can inadvertently become barriers to new technologies that do not work the same way as existing vaccines. This is particularly true when these tests are based upon circularly-defined ‘reference’ or, even worse, proprietary reagents. The situation with inactivated influenza vaccines is a good example of this phenomenon. The most frequently used tests to define vaccine-induced immunity are all serologic assays: hemagglutination inhibition (HI), single radial hemolysis (SRH) and microneutralization (MN). The first two, and particularly the HI assay, have achieved reference status and criteria have been established in many jurisdictions for their use in licensing new vaccines and to compare the performance of different vaccines. However, all of these assays are based on biological reagents that are notoriously difficult to standardize and can vary substantially by geography, by chance (i.e. developing reagents in eggs that may not antigenitically match wild-type viruses) and by intention (ie: choosing reagents that yield the most favorable results). This review describes attempts to standardize these assays to improve their performance as surrogates, the dangers of over-reliance on ‘reference’ serologic assays, the ways that manufacturers can exploit the existing regulatory framework to make their products ‘look good’ and the implications of this long-established system for the introduction of novel influenza vaccines.

Transcriptomic signatures of cellular and humoral immune responses in older adults after seasonal influenza vaccination identified by data-driven clustering

PBMC transcriptomes after influenza vaccination contain valuable information about factors affecting vaccine responses. However, distilling meaningful knowledge out of these complex datasets is often difficult and requires advanced data mining algorithms. We investigated the use of the data-driven Weighted Gene Correlation Network Analysis (WGCNA) gene clustering method to identify vaccine response-related genes in PBMC transcriptomic datasets collected from 138 healthy older adults (ages 50-74) before and after 2010-2011 seasonal trivalent influenza vaccination. WGCNA separated the 14,197 gene dataset into 15 gene clusters based on observed gene expression patterns across subjects. Eight clusters were strongly enriched for genes involved in specific immune cell types and processes, including B cells, T cells, monocytes, platelets, NK cells, cytotoxic T cells, and antiviral signaling. Examination of gene cluster membership identified signatures of cellular and humoral responses to seasonal influenza vaccination, as well as pre-existing cellular immunity. The results of this study illustrate the utility of this publically available analysis methodology and highlight genes previously associated with influenza vaccine responses (e.g., CAMK4, CD19), genes with functions not previously identified in vaccine responses (e.g., SPON2, MATK, CST7), and previously uncharacterized genes (e.g. CORO1C, C8orf83) likely related to influenza vaccine-induced immunity due to their expression patterns.

The effect of frailty on HAI response to influenza vaccine among community-dwelling adults ≥ 50 years of age

The immune response to vaccine antigens is less robust in older adults because of changes in the aging immune system. Frailty, the multi-dimensional syndrome marked by losses in function and physiological reserve, is increasingly prevalent with advancing age. Frailty accelerates this immunosenescence but the consequence of frailty on immune response specific to influenza vaccine among older adults, is mixed. An observational, prospective study of 114 adults was conducted in the fall of 2013 to assess the association of physical frailty with immune response to standard dose influenza vaccine in community-dwelling adults ≥ 50 years of age. Participants were stratified by age (<65 years and ≥65 years), and vaccine strain (Influenza A/H1N1, A/H3N2 and B) was analyzed separately adjusting for body mass index (BMI) and baseline log₂ hemagglutination inhibition (HAI) titers. Overall, immune responses were lower among those ≥65 years of age than those <65 years. Among those ≥65 years there were no significant differences between frail and non-frail individuals in seroprotection or seroconversion for any influenza strain. Frail individuals <65 years of age compared with non-frail individuals were more likely to be seroprotected and to seroconvert post vaccination. Linear regression models show the same pattern of significant differences between frail and non-frail for those <65 years but no significant differences between frailty groups for those ≥65 years. Additional research may elucidate the reasons for the differences observed between younger frail and non-frail adults.