Correlates of Protection against Influenza in the Elderly: Results from an Influenza Vaccine Efficacy Trial

Immunogenicity and Safety of Influenza and COVID-19 Multicomponent Vaccine in Adults ≥50 Years: A Randomized Clinical Trial

Importance

Uptake of recommended seasonal influenza and COVID-19 vaccines remains suboptimal.

Objective

To assess the immunogenicity and safety of an investigational mRNA-1083 vaccine against seasonal influenza and SARS-CoV-2 in adults 50 years and older.

Design, Setting, and Participants

This phase 3, randomized, observer-blinded trial was conducted across 146 US sites in adults 50 years and older enrolled between October 19, 2023, and November 21, 2023. Data extraction was complete on April 9, 2024.

Interventions

Participants in 2 age cohorts (≥65 years and 50-64 years) were randomly assigned (1:1) to receive mRNA-1083 plus placebo or coadministered licensed quadrivalent seasonal influenza (≥65 years: high-dose quadrivalent inactivated influenza vaccine [HD-IIV4]; 50-64 years: standard-dose IIV4 [SD-IIV4]) and COVID-19 (all ages: mRNA-1273) vaccines.

Main Outcomes and Measures

The primary objectives were to demonstrate the noninferiority of humoral immune responses following mRNA-1083 vs comparators against vaccine-matched strains at day 29 and to evaluate the reactogenicity and safety of mRNA-1083. Secondary objectives included demonstration of superiority of humoral immune responses elicited by mRNA-1083 relative to comparators at day 29.

Results

Overall, 8015 participants were enrolled and vaccinated (4017 aged ≥65 y and 3998 aged 50-64 y). Among adults 65 years and older and 50 to 64 years, the median age was 70 and 58 years, 54.2% and 58.8% were female, 18.4% and 26.7% were Black or African American, and 13.9% and 19.3% were Hispanic or Latino, respectively. Noninferior immunogenicity of mRNA-1083 was demonstrated against all vaccine-matched influenza and SARS-CoV-2 strains based on lower bound of the 97.5% CI of the geometric mean ratio greater than 0.667 and lower bound of the 97.5% CI of the seroconversion/seroresponse rate difference greater than -10%. mRNA-1083 elicited higher immune responses than SD-IIV4 (50-64 years) for all 4 influenza strains and HD-IIV4 (≥65 years) for 3 influenza strains (A/H1N1, A/H3N2, B/Victoria) and against SARS-CoV-2 (all ages). Solicited adverse reactions were numerically higher in frequency and severity after mRNA-1083 vaccination than comparators in both age cohorts (≥65 y: 83.5% and 78.1%; 50-64 y: 85.2% and 81.8%); most were grade 1 or 2 in severity and of short duration. No safety concerns were identified.

Conclusions and Relevance

In this study, mRNA-1083 met noninferiority criteria and induced higher immune responses than recommended standard care influenza (standard and high dose) and COVID-19 vaccines against all 4 influenza strains (among those ages 50-64 y), the 3 clinically relevant influenza strains (among those aged ≥65 y), and SARS-CoV-2 (all ages), with an acceptable tolerability and safety profile.

Trial Registration

ClinicalTrials.gov Identifier: NCT06097273.

Influential drivers of the cost-effectiveness of respiratory syncytial virus vaccination in European older adults: a multi-country analysis

BACKGROUND

We aimed to identify influential drivers of the cost-effectiveness of older adult respiratory syncytial virus (RSV) vaccination in Denmark, Finland, the Netherlands and Valencia-Spain.

METHODS

A static multi-cohort model was parameterised using country- and age-specific hospitalisations using three approaches: (A) the International Classification of Diseases (ICD)-coded hospitalisations, (B) laboratory RSV-confirmed hospitalisations and (C) time-series modelling (TSM). Plausible hypothetical RSV vaccine characteristics were derived from two protein subunit vaccines for adults aged ≥60 years. A full incremental analysis was conducted by comparing three RSV vaccination strategies: (1) in adults aged ≥60 years ("60y+"); (2) in adults aged ≥65 years ("65y+"); (3) in adults aged ≥75 years ("75y+") to "no intervention" and to each other. Both costs and quality-adjusted life-years (QALYs) were discounted at country-specific discount rates and the analysis was conducted from both the healthcare payers' and societal perspectives. Value of information, probabilistic sensitivity and scenario analyses identified influential drivers.

RESULTS

Besides vaccine price, the hospitalisation estimates were most influential: (A) Using adjusted RSV-ICD-coded hospitalisations at a vaccine price of €150 per dose, no intervention was cost-effective up to willingness-to-pay (WTP) values of €150,000 per QALY gained in Denmark and the Netherlands, and up to €124,000 per QALY gained in Finland. (B) Using the adjusted RSV-confirmed dataset, the findings were consistent in Denmark and comparable in Finland. In Spain-Valencia, the 75y+ strategy became cost-effective at WTP >€55,000. (C) Using TSM-based estimates, the 75y+ strategy was cost-effective at WTP >€45,000, >€101,000, >€41,000 and >€114,000 in Denmark, Finland, the Netherlands and Spain-Valencia, respectively. Sensitivity analyses showed that the (in-hospital) case fatality ratio and the specification of its age dependency were both influential. Duration of protection was found more influential than a variety of plausible waning patterns over the duration of protection.

CONCLUSIONS

Data gaps and uncertainties on the RSV-related burden in older adults persist and influence the cost-effectiveness of RSV vaccination. More refined age- and country-specific data on the RSV attributable burden are crucial to aid decision making.

Safety and immunogenicity of mRNA-based seasonal influenza vaccines formulated to include multiple A/H3N2 strains with or without the B/Yamagata strain in US adults aged 50-75 years: a phase 1/2, open-label, randomised trial

BACKGROUND

Inclusion of additional influenza A/H3N2 strains in seasonal influenza vaccines could expand coverage against multiple, antigenically distinct, cocirculating A/H3N2 clades and potentially replace the no longer circulating B/Yamagata strain. We aimed to evaluate the safety and immunogenicity of three next-generation seasonal influenza mRNA vaccines with different compositions that encode for haemagglutinins of multiple A/H3N2 strains, with or without the B/Yamagata strain, in adults.

METHODS

This randomised, open-label, phase 1/2 trial enrolled healthy adults aged 50-75 years across 22 sites in the USA. Participants were randomly assigned (1:1:1:1:1:1:1) via interactive response technology to receive a single dose of mRNA-1011.1 (pentavalent; containing one additional A/H3N2 strain [Newcastle]), mRNA-1011.2 (quadrivalent; B/Yamagata replaced with one additional A/H3N2 strain [Newcastle]), mRNA-1012 at one of two dose levels (pentavalent; B/Yamagata replaced with two additional A/H3N2 strains [Newcastle and Hong Kong]), or one of three quadrivalent mRNA-1010 controls each encoding one of the A/H3N2 study strains. The primary outcomes were safety, evaluated in all randomly assigned participants who received a study vaccination (safety population), and reactogenicity, evaluated in all participants from the safety population who contributed any solicited adverse reaction data (solicited safety population). The secondary outcome was humoral immunogenicity of investigational mRNA vaccines at day 29 versus mRNA-1010 control vaccines based on haemagglutination inhibition antibody (HAI) assay in the per-protocol population. Here, we summarise findings from the planned interim analysis after participants had completed day 29. The study is registered with ClinicalTrials.gov, NCT05827068, and is ongoing.

FINDINGS

Between March 27 and May 9, 2023, 1183 participants were screened for eligibility, 699 (59·1%) were randomly assigned, and 696 (58·8%) received vaccination (safety population, n=696; solicited safety population, n=694; per-protocol population, n=646). 382 (55%) of the 696 participants in the safety population self-reported as female and 314 (45%) as male. Frequencies of solicited adverse reactions were similar across vaccine groups; 551 (79%) of 694 participants reported at least one solicited adverse reaction within 7 days after vaccination and 83 (12%) of 696 participants reported at least one unsolicited adverse event within 28 days after vaccination. No vaccine-related serious adverse events or deaths were reported. All three next-generation influenza vaccines elicited robust antibody responses against vaccine-matched influenza A and B strains at day 29 that were generally similar to mRNA-1010 controls, and higher responses against additional A/H3N2 strains that were not included within respective mRNA-1010 controls. Day 29 geometric mean fold rises in HAI titres from day 1 against vaccine-matched A/H3N2 strains were 3·0 (95% CI 2·6-3·6; Darwin) and 3·1 (2·6-3·8; Newcastle) for mRNA-1011.1; 3·3 (2·7-4·1; Darwin) and 4·2 (3·4-5·2; Newcastle) for mRNA-1011.2; 3·4 (2·9-4·0; Darwin), 4·5 (3·6-5·5; Newcastle), and 5·1 (4·2-6·2; Hong Kong) for mRNA-1012 50·0 μg; and 2·6 (2·2-3·1; Darwin), 3·7 (3·0-4·6; Newcastle), and 4·1 (3·3-5·1; Hong Kong) for mRNA-1012 62·5 μg. Inclusion of additional A/H3N2 strains did not reduce responses against influenza A/H1N1 or influenza B strains, and removal of B/Yamagata did not affect responses to B/Victoria.

INTERPRETATION

These data support the continued clinical development of mRNA-based next-generation seasonal influenza vaccines with broadened influenza A/H3N2 strain coverage.

FUNDING

Moderna.

Formulation development of a stable influenza recombinant neuraminidase vaccine candidate

Current influenza vaccines could be augmented by including recombinant neuraminidase (rNA) protein antigen to broaden protective immunity and improve efficacy. Toward this goal, we investigated formulation conditions to optimize rNA physicochemical stability. When rNA in sodium phosphate saline buffer (NaPBS) was frozen and thawed (F/T), the tetrameric structure transitioned from a "closed" to an "open" conformation, negatively impacting functional activity. Hydrogen deuterium exchange experiments identified differences in anchorage binding sites at the base of the open tetramer, offering a structural mechanistic explanation for the change in conformation and decreased functional activity. Change to the open configuration was triggered by the combined stresses of acidic pH and F/T. The desired closed conformation was preserved in a potassium phosphate buffer (KP), minimizing pH drop upon freezing and including 10% sucrose to control F/T stress. Stability was further evaluated in thermal stress studies where changes in conformation were readily detected by ELISA and size exclusion chromatography (SEC). Both tests were suitable indicators of stability and antigenicity and considered potential critical quality attributes (pCQAs). To understand longer-term stability, the pCQA profiles from thermally stressed rNA at 6 months were modeled to predict stability of at least 24-months at 5°C storage. In summary, a desired rNA closed tetramer was maintained by formulation selection and monitoring of pCQAs to produce a stable rNA vaccine candidate. The study highlights the importance of understanding and controlling vaccine protein structural and functional integrity.

Seasonal influenza vaccines: Variability of immune responses to B lineage viruses

Although influenza A viruses predominate globally, influenza B viruses are responsible for a significant and often underappreciated burden. Despite this, immunity to influenza B viruses remains understudied, and there is a perception that vaccine-mediated immune responses to influenza B strains are less robust than influenza A strains. This targeted literature review examines this concept using data from pivotal phase 3 immunogenicity studies on currently licensed seasonal influenza vaccines and explores several explanations for this phenomenon, including immune exposure history, assay limitations, virus-related properties inherent to B lineages, and strain mismatch. Overall, studies demonstrated vaccines induce variable and sometimes less robust immune responses to influenza B strains; however, further studies are needed to fully confirm and understand these observations. In identifying the potential causes of variable performance of current vaccines against influenza, this review aims to guide vaccine development to enhance overall vaccine performance and reduce disease burden worldwide.

Boosting neuraminidase immunity in the presence of hemagglutinin with the next generation of influenza vaccines

Neuraminidase (NA), the second most abundant surface glycoprotein on the influenza virus, plays a key role in viral replication and propagation. Despite growing evidence showing that NA-specific antibodies correlate with resistance to disease in humans, current licensed vaccines focus almost entirely on the hemagglutinin (HA) antigen. Here, we demonstrate that recombinant NA (rNA) protein is highly immunogenic in both naïve mice and ferrets, as well as in pre-immune ferrets, irrespective of the level of match with preexisting immunity. Ferrets vaccinated with rNA developed mild influenza disease symptoms upon challenge with human H3N2 influenza virus, and anti-NA antibody responses appeared correlated with reduction in disease severity. The addition of rNA to a quadrivalent HA-based vaccine induced robust NA-specific humoral immunity in ferrets, while retaining the ability to induce HA-specific immunity. These results demonstrate that the addition of rNA is a viable option to increase immunogenicity and potentially efficacy versus currently licensed influenza vaccines by means of boosting NA immunity.

Time of day for vaccination, outcomes, and relative effectiveness of high-dose vs. standard-dose quadrivalent influenza vaccine: A post hoc analysis of the DANFLU-1 randomized clinical trial

OBJECTIVES

Morning influenza vaccination enhances antibody response. In this post hoc analysis of the DANFLU-1 trial, we sought to evaluate the association between time of day for vaccination (ToV) and outcomes and whether ToV modified the relative effectiveness of high-dose (QIV-HD) vs. standard-dose (QIV-SD) quadrivalent influenza vaccine.

METHODS

DANFLU-1 was a pragmatic feasibility trial of QIV-HD vs. QIV-SD. Outcomes included hospitalizations and mortality. For subgroup analysis, the population was dichotomized at median ToV into two groups (early and late).

RESULTS

The study population included 12,477 participants. Mean age was 71.7 ± 3.9 years with 5877 (47.1%) female participants. Median ToV was 11.29 AM. Earlier ToV was associated with fewer respiratory hospitalizations independent of vaccine type, which persisted in adjusted analysis (IRR 0.88 per 1-hour decrement (95% CI 0.78- 0.98, p = 0.025). No effect modification by continuous or dichotomous ToV was found. In subgroup analysis, effects consistently favored QIV-HD against hospitalizations for pneumonia or influenza (early: IRR 0.30; late: 0.29), all-cause hospitalizations (early: IRR 0.87; late: 0.86), and mortality (early: HR 0.53; late: 0.50).

CONCLUSION

In this exploratory post hoc analysis, earlier ToV was associated with fewer respiratory hospitalizations. The relative effectiveness of QIV-HD vs. QIV-SD was not modified by ToV. Further research is needed to confirm findings.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT05048589.

Comparison of immunogenicity of adjuvanted and high dose influenza vaccination in long-term care facility residents

Background

The CDC recommends the more immunogenic adjuvanted and high-dose flu vaccines over standard-dose, non-adjuvanted vaccines for individuals above 65 years old. The current study compares adjuvanted trivalent inactivated flu vaccine (aTIV, FLUAD) versus high-dose flu vaccine (HD-IIV3, FLUZONE HD) to determine if they met non-inferiority standards for older long-term care facility (LTCF) residents.

Methods

We collected blood from long-term care facility residents participating in a randomized 1:1 active control trial comparing MF59C.1 adjuvanted trivalent inactivated flu vaccine, aTIV versus HD-IIV3 over the course of two flu seasons, 2018-2019 and 2019-2020 (Trial, NCT03694808). We assessed humoral immunity at set time points via hemagglutinin inhibition assays (HAI) and anti-neuraminidase (enzyme-linked lectin assays (ELLA)). The recombinant influenza vaccine (RIV, Flublok) was assessed similarly in year two for a small number of participants who were carried over from year 1 (n=32).

Results

We enrolled 387 volunteers and administered either aTIV (n=194), HD-IIV3 (n=193) over the course of the 2018-2019 and 2019-2020 flu seasons. Among those enrolled and randomized in year one, a subset were administered RIV and studied in year two (n = 32). At 28 days post-vaccination, aTIV exhibited non-inferiority to HD-IIV3 for HAI for both H1N1 and H3N2 strains (GMT ratios (95% CI) for HD-IIV3/aTIV of 1.03(0.76, 1.4) and 1.04(0.73, 1.48), respectively; both 95% CI upper bounds < 1.5 to meet non-inferiority criteria) but not for Influenza B (GMT ratio (95% CI) = 1.21 (0.91, 1.61)). Non-inferiority criteria for HAI seroconversion were not met for any of the three strains. Applying the same non-inferiority criteria to neuraminidase inhibition (NI), both day 28 titer and seroconversion in aTIV were non-inferior to HD-IIV3 for H1N1 and H3N2 strains.

Conclusions

Both aTIV and HD-IIV3 elicited similar immune responses with robust antibody responses. For the primary outcome, aTIV is non-inferior to HD-IIV3 for HAI titer of H1N1 and H3N2 but failed to meet non-inferiority criteria for Influenza B and seroconversion for all assessed strains. For the secondary outcome, aTIV was non-inferior to HD-IIV3 for both titer and seroconversion of anti-neuraminidase for both H1N1 and H3N2.

Influenza Vaccine Immune Response in Patients With High-Risk Cardiovascular Disease: A Secondary Analysis of the INVESTED Randomized Clinical Trial

Importance

High-dose trivalent compared with standard-dose quadrivalent influenza vaccine did not significantly reduce all-cause mortality or cardiopulmonary hospitalizations in patients with high-risk cardiovascular disease in the INVESTED trial. Whether humoral immune response to influenza vaccine is associated with clinical outcomes is unknown.

Objective

To examine the antibody response to high-dose trivalent compared with standard-dose quadrivalent inactivated influenza vaccine and its associations with clinical outcomes.

Design, Setting, and Participants

This secondary analysis is a prespecified analysis of the immune response substudy of the randomized, double-blind, active-controlled INVESTED trial, which was conducted at 157 sites in the United States and Canada over 3 influenza seasons between September 2016 and January 2019. Antibody titers were determined by hemagglutination inhibition assays at randomization and 4 weeks during the 2017-2018 and 2018-2019 seasons. Eligibility criteria included recent acute myocardial infarction or heart failure hospitalization and at least 1 additional risk factor. Data were analyzed from February 2023 to June 2023.

Main Outcomes and Measures

Mean antibody titer change, seroprotection (antibody titer level ≥1:40) and seroconversion (≥4-fold increase in titer) at 4 weeks, and the association between seroconversion status and the risk for adverse clinical outcomes.

Interventions

High-dose trivalent or standard-dose quadrivalent inactivated influenza vaccine, with revaccination up to 3 seasons.

Results

Antibody data were available for 658 of 5260 randomized participants (12.5%; mean [SD] age, 66.2 [11.4] years; 507 male [77.1%], 151 female [22.9%]; 348 with heart failure [52.9%]). High-dose vaccine was associated with an increased magnitude in antibody titers for A/H1N1, A/H3N2, and B-type antigens compared with standard dose. More than 92% of all participants achieved seroprotection for each of the contained antigens, while seroconversion rates were higher in participants who received high-dose vaccine. Seroconversion for any antigen was not associated with the risk for cardiopulmonary hospitalizations or all-cause mortality (hazard ratio, 1.09; 95% CI, 0.79-1.53; P = .59), irrespective of randomized treatment (P = .38 for interaction).

Conclusions and Relevance

High-dose vaccine elicited a more robust humoral response in patients with heart failure or prior myocardial infarction enrolled in the INVESTED trial, with no association between seroconversion status and the risk for cardiopulmonary hospitalizations or all-cause mortality. Vaccination to prevent influenza remains critical in high-risk populations.

Trial Registration

ClinicalTrials.gov Identifier: NCT02787044.

Vaccines for the Elderly and Vaccination Programs in Europe and the United States

The share of the elderly population is growing worldwide as life expectancy increases. Immunosenescence and comorbidities increase infectious diseases' morbidity and mortality in older adults. Here, we aimed to summarize the latest findings on vaccines for the elderly against herpes zoster, influenza, respiratory syncytial virus (RSV), COVID-19, and pneumococcal disease and to examine vaccine recommendation differences for this age group in Europe and the United States. PubMed was searched using the keywords "elders" and "vaccine" alongside the disease/pathogen in question and paraphrased or synonymous terms. Vaccine recommendations were also sought in the European and US Centers for Disease Control and Prevention databases. Improved vaccines, tailored for the elderly, mainly by using novel adjuvants or by increasing antigen concentration, are now available. Significant differences exist between immunization policies, especially between European countries, in terms of the recipient's age, number of doses, vaccination schedule, and implementation (mandatory or recommended). Understanding the factors that influence the immune response to vaccination in the elderly may help to design vaccines that offer long-term protection for this vulnerable age group. A consensus-based strategy in Europe could help to fill the gaps in immunization policy in the elderly, particularly regarding vaccination against RSV and pneumococcus.

Immunogenicity of Enhanced Influenza Vaccines Against Mismatched Influenza Strains in Older Adults: A Review of Randomized Controlled Trials

Antigenic drift is a major driver of viral evolution and a primary reason why influenza vaccines must be reformulated annually. Mismatch between vaccine and circulating viral strains negatively affects vaccine effectiveness and often contributes to higher rates of influenza-related hospitalizations and deaths, particularly in years dominated by A(H3N2). Several countries recommend enhanced influenza vaccines for older adults, who are at the highest risk of severe influenza complications and mortality. The immunogenicity of enhanced vaccines against heterologous A(H3N2) strains has been examined in nine studies to date. In six studies, an enhanced, licensed MF59-adjuvanted trivalent inactivated influenza vaccine (aIIV3) consistently increased heterologous antibody titers relative to standard influenza vaccine, with evidence of a broad heterologous immune response across multiple genetic clades. In one study, licensed high-dose trivalent inactivated influenza vaccine (HD-IIV3) also induced higher heterologous antibody titers than standard influenza vaccine. In a study comparing a higher dose licensed quadrivalent recombinant influenza vaccine (RIV4) with HD-IIV3 and aIIV3, no significant differences in antibody titers against a heterologous strain were observed, although seroconversion rates were higher with RIV4 versus comparators. With the unmet medical need for improved influenza vaccines, the paucity of studies especially with enhanced vaccines covering mismatched strains highlights a need for further investigation of cross-protection in older adults.

Antigen spacing on protein nanoparticles influences antibody responses to vaccination

Immunogen design approaches aim to control the specificity and quality of antibody responses elicited by next-generation vaccines. Here, we use computational protein design to generate a nanoparticle vaccine platform based on the receptor-binding domain (RBD) of influenza hemagglutinin (HA) that enables precise control of antigen conformation and spacing. HA RBDs are presented as either monomers or native-like closed trimers that are connected to the underlying nanoparticle by a rigid linker that is modularly extended to precisely control antigen spacing. Nanoparticle immunogens with decreased spacing between trimeric RBDs elicit antibodies with improved hemagglutination inhibition and neutralization potency as well as binding breadth across diverse H1 HAs. Our "trihead" nanoparticle immunogen platform provides insights into anti-HA immunity, establishes antigen spacing as an important parameter in structure-based vaccine design, and embodies several design features that could be used in next-generation vaccines against influenza and other viruses.

Population immunity predicts evolutionary trajectories of SARS-CoV-2

The large-scale evolution of the SARS-CoV-2 virus has been marked by rapid turnover of genetic clades. New variants show intrinsic changes, notably increased transmissibility, and antigenic changes that reduce cross-immunity induced by previous infections or vaccinations. How this functional variation shapes global evolution has remained unclear. Here, we establish a predictive fitness model for SARS-CoV-2 that integrates antigenic and intrinsic selection. The model is informed by tracking of time-resolved sequence data, epidemiological records, and cross-neutralization data of viral variants. Our inference shows that immune pressure, including contributions of vaccinations and previous infections, has become the dominant force driving the recent evolution of SARS-CoV-2. The fitness model can serve continued surveillance in two ways. First, it successfully predicts the short-term evolution of circulating strains and flags emerging variants likely to displace the previously predominant variant. Second, it predicts likely antigenic profiles of successful escape variants prior to their emergence.

Sex-Specific Immune Responses to Seasonal Influenza Vaccination in Diabetic Individuals: Implications for Vaccine Efficacy

Seasonal influenza vaccination has different implications on the immune response depending on the comorbidities. Diabetes is one such critical disease that increases the patient's susceptibility to influenza and suppresses vaccine efficacy and immunity. The sex of the individuals also plays a definitive role in the immune responses to both the vaccine and the infection. This study aims to understand the efficacy of the seasonal vaccine against influenza in diabetic groups and undergoing immune mechanisms in different sexes (females and males). In this study, we are reporting about a switching of the immune response of the infected and vaccinated diabetic females towards stronger Th1/Th17 responses with suppressed humoral immunity. They show increased cDC1, enhanced proinflammatory activities within T cells, CD8T activation, Th17 proliferation, and the majority of IgG2 antibody subtypes with reduced neutralization potential. Males with diabetes exhibit enhanced humoral Th2-immunity than the nondiabetic group. They exhibit higher cDC2, and DEC205 levels within them with an increase in plasma B lymphocytes, higher IgG1 subtypes in plasma cells, and influenza-hemagglutinin-specific IgG titer with stronger virus neutralization potential. Males with diabetes recovered better than the females as observed from the changes in their body weight. This study highlights the critical immune mechanisms and sex-specific swapping of their preferred immune response pathways against influenza after vaccination during diabetes. We propose a need for a sex-specific customized vaccine regimen to be implemented against influenza for individuals having diabetes to exploit the manifested strength and weakness in their protective immunity.

Humoral and Cellular Immunity Induced by Adjuvanted and Standard Trivalent Influenza Vaccine in Older Nursing Home Residents

BACKGROUND

Despite wide use of adjuvanted influenza vaccine in nursing home residents (NHR), little immunogenicity data exist for this population.

METHODS

We collected blood from NHR (n = 85) living in nursing homes participating in a cluster randomized clinical trial comparing MF59-adjuvanted trivalent inactivated influenza vaccine (aTIV) with nonadjuvanted vaccine (TIV) (parent trial, NCT02882100). NHR received either vaccine during the 2016-2017 influenza season. We assessed cellular and humoral immunity using flow cytometry and hemagglutinin inhibition, antineuraminidase (enzyme-linked lectin assay), and microneutralization assays.

RESULTS

Both vaccines were similarly immunogenic and induced antigen-specific antibodies and T cells, but aTIV specifically induced significantly larger 28 days after vaccination (D28) titers against A/H3N2 neuraminidase than TIV.

CONCLUSIONS

NHRs respond immunologically to TIV and aTIV. From these data, the larger aTIV-induced antineuraminidase response at D28 may help explain the increased clinical protection observed in the parent clinical trial for aTIV over TIV in NHR during the A/H3N2-dominant 2016-2017 influenza season. Additionally, a decline back to prevaccination titers at 6 months after vaccination emphasizes the importance of annual vaccination against influenza.

CLINICAL TRIALS REGISTRATION

NCT02882100.

Age-dependent changes in T follicular helper cells shape the humoral immune response to vaccination

Vaccination is an excellent strategy to limit the morbidity and mortality associated with infectious disease. Vaccination creates protective, long-lived antibody-mediated immunity by inducing the germinal centre response, an intricate immune reaction that produces memory B cells and long-lived antibody-secreting plasma cells that provide protection against (re)infection. The magnitude and quality of the germinal centre response declines with age, contributing to poor vaccine-induced immunity in older individuals. T follicular helper cells are essential for the formation and function of the germinal centre response. This review will discuss how age-dependent changes in T follicular helper cells influence the germinal centre response, and the evidence that age-dependent changes need not be a barrier to successful vaccination in the later years of life.

Immunogenicity of adjuvanted versus high-dose inactivated influenza vaccines in older adults: a randomized clinical trial

BACKGROUND

Adjuvanted inactivated influenza vaccine (aIIV) and high-dose inactivated influenza vaccine (HD-IIV) are U.S.-licensed for adults aged ≥ 65 years. This study compared serum hemagglutination inhibition (HAI) antibody titers for the A(H3N2) and A(H1N1)pdm09 and B strains after trivalent aIIV3 and trivalent HD-IIV3 in an older adult population.

RESULTS

The immunogenicity population included 342 participants who received aIIV3 and 338 participants who received HD-IIV3. The proportion of participants that seroconverted to A(H3N2) vaccine strains after allV3 (112 participants [32.8%]) was inferior to the proportion of participants that seroconverted after HD-IIV3 (130 participants [38.5%]) at day 29 after vaccination (difference, - 5.8%; 95%CI, - 12.9% to 1.4%). There were no significant differences between the vaccine groups in percent seroconversion to A(H1N1)pdm09 or B vaccine strains, in percent seropositivity for any of the strains, or in post-vaccination GMT for the A(H1N1)pdm09 strain. The GMTs for the post-vaccination A(H3N2) and B strains were higher after HD-IIV than after aIIV3.

CONCLUSIONS

Overall immune responses were similar after aIIV3 and HD-IIV3. For the primary outcome, the aIIV3 seroconversion rate for H3N2 did not meet noninferiority criteria compared with HD-IIV3, but the HD-IIV3 seroconversion rate was not statistically superior to the aIIV3 seroconversion rate.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03183908.

Antigen spacing on protein nanoparticles influences antibody responses to vaccination

Immunogen design approaches aim to control the specificity and quality of antibody responses to enable the creation of next-generation vaccines with improved potency and breadth. However, our understanding of the relationship between immunogen structure and immunogenicity is limited. Here we use computational protein design to generate a self-assembling nanoparticle vaccine platform based on the head domain of influenza hemagglutinin (HA) that enables precise control of antigen conformation, flexibility, and spacing on the nanoparticle exterior. Domain-based HA head antigens were presented either as monomers or in a native-like closed trimeric conformation that prevents exposure of trimer interface epitopes. These antigens were connected to the underlying nanoparticle by a rigid linker that was modularly extended to precisely control antigen spacing. We found that nanoparticle immunogens with decreased spacing between closed trimeric head antigens elicited antibodies with improved hemagglutination inhibition (HAI) and neutralization potency as well as binding breadth across diverse HAs within a subtype. Our "trihead" nanoparticle immunogen platform thus enables new insights into anti-HA immunity, establishes antigen spacing as an important parameter in structure-based vaccine design, and embodies several design features that could be used to generate next-generation vaccines against influenza and other viruses.

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.

Elevation of circulating TNF receptor 2 in cancer: A systematic meta-analysis for its potential as a diagnostic cancer biomarker

High Tumor Necrosis Factor Receptor 2 (TNFR2) expression is characteristic of diverse malignant cells during tumorigenesis. The protein is also expressed by many immunosuppressive cells during cancer development, allowing cancer immune escape. A growing body of evidence further suggests a correlation between the circulating form of this protein and cancer development. Here we conducted a systematic meta-analysis of cancer studies published up until 1st October 2022, in which the circulating soluble TNFR2 (sTNFR2) concentrations in patients with cancers were recorded and their association with cancer risk was assessed. Of the 14,615 identified articles, 44 studies provided data on the correlation between cancer risk and the level of circulating sTNFR2. The pooled means comparison showed a consistently significant increase in the levels of sTNFR2 in diverse cancers when compared to healthy controls. These included colorectal cancer, ovarian cancer, breast cancer, non-Hodgkin's lymphoma, Hodgkin's lymphoma, lung cancer, hepatocarcinoma, and glioblastoma. In a random-effect meta-analysis, the cancer-specific odd ratios (OR) showed significant correlations between increased circulating sTNFR2 levels and the risk of colorectal cancer, non-Hodgkin's lymphoma, and hepatocarcinoma at 1.59 (95% CI:1.20-2.11), 1.98 (95% CI:1.49-2.64) and 4.32 (95% CI:2.25-8.31) respectively. The overall result showed an association between circulating levels of sTNFR2 and the risk of developing cancer at 1.76 (95% CI:1.53-2.02). This meta-analysis supports sTNFR2 as a potential diagnostic biomarker for cancer, albeit with different predictive strengths for different cancer types. This is consistent with a potential key role for TNFR2 involvement in cancer development.

Immunological Correlates of Prevention of the Onset of Seasonal H3N2 Influenza

On influenza virus infection or vaccination, immune responses occur, including the production of antibodies with various functions that contribute to protection from seasonal influenza virus infection. In the current study, we attempted to identify the antibody functions that play a central role in preventing the onset of seasonal influenza by comparing the levels of several antibody titers for different antibody functions between 5 subclinically infected individuals and 16 patients infected with seasonal H3N2 virus. For antibody titers before influenza virus exposure, we found that the nAb titers and enzyme-linked immunosorbent assay titers against hemagglutinin and neuraminidase (NA) proteins in the subclinically infected individuals were significantly higher than those in the patients, whereas the NA inhibition titers and antibody-dependent cellular cytotoxicity activities did not significantly differ between subclinically infected individuals and infected patients. These results suggest that nAb and enzyme-linked immunosorbent assay titers against hemagglutinin and NA serve as correlates of symptomatic influenza infection.

Effectiveness of Comirnaty® Vaccine and Correlates of Immunogenicity and Adverse Reactions: A Single-Center Prospective Case Series Study

The literature suggests that real-world data on the effectiveness and safety of the BNT162b2 vaccine depend on the characteristics of the vaccinated volunteers. The purpose of this study was to evaluate antibody responses and kinetics, established association with sociodemographic and clinical characteristics, and adverse reactions after complete vaccination with the BNT162b2 vaccine. A single-center prospective case series study was conducted with 112 eligible volunteers who were institutionalized elderly and health care workers with had a negative anti-SARS-CoV-2 IgG test prior to receiving the first dose of vaccine. At least one serological antibody test after each dose of vaccine was performed. Volunteers with a positive SARS-CoV-2 PCR test before vaccination were excluded. A chemiluminescent immunoassay anti-S1 antibody assay performed a serological evaluation. Both vaccine doses elicited positive IgG antibodies 3799.0 ± 2503.0 AU/mL and 8212.0 ± 4731.0 AU/mL after 20 days of the first and second doses of BNT162b2, respectively. Comirnaty® vaccine induced an immune response with antibody production against SARS-CoV-2 in 100% of participants, regardless of age (Spearman rho = −0.10, p-value = 0.312), body mass index (Spearman rho = 0.05, p-value = 0.640), blood group first dose (p-value for Kruskal−Wallis test = 0.093) and second dose (p-value for Kruskal−Wallis test = 0. 268), number of drugs (Spearman rho = −0.07, p-value = 0.490), and number of chronic diseases first dose (p-value for Kruskal−Wallis test = 0.632) and second dose (p-value for Kruskal−Wallis test = 0.510). IgG antibodies to SARS-CoV-2 were intensely elevated after the second administration of the BNT162b2 vaccine. The higher the titer of anti-peptide IgG antibodies generated after the first dose of vaccine, the higher the titer generated by the second dose of vaccine (Spearman rho = 0.86, p-value < 0.001) and the total antibody titer (Spearman rho = 0.93, p-value < 0.001). Furthermore, no serious adverse effects were reported among participants, although mild to moderate adverse effects (local or systemic) were reported after both doses of the BNT162b2 vaccine, being more frequent after the first dose of the vaccine. No participants showed a positive PCR. The BNT162b2 vaccine induces a robust and rapid antibody response regardless of participant characteristics. The second dose might be especially important because of the increased immunogenicity it produces and the possible temporal distancing of the interval between doses. In general, the vaccines were well tolerated.

Inactivated Whole Virus Particle Influenza Vaccine Induces Anti-Neuraminidase Antibodies That May Contribute to Cross-Protection against Heterologous Virus Infection

Despite the use of vaccines, seasonal influenza remains a risk to public health. We previously proposed the inactivated whole virus particle vaccine (WPV) as an alternative to the widely used split vaccine (SV) for the control of seasonal and pandemic influenza based on the superior priming potency of WPV to that of SV. In this study, we further examined and compared the immunological potency of monovalent WPV and SV of A/California/7/2009 (X-179A) (H1N1) pdm09 (CA/09) to generate immune responses against heterologous viruses, A/Singapore/GP1908/2015 (IVR-180) (H1N1) pdm09 (SG/15), and A/duck/Hokkaido/Vac-3/2007 (H5N1) (DH/07) in mice. Following challenge with a lethal dose of heterologous SG/15, lower virus titer in the lungs and milder weight loss were observed in WPV-vaccinated mice than in SV-vaccinated ones. To investigate the factors responsible for the differences in the protective effect against SG/15, the sera of vaccinated mice were analyzed by hemagglutination-inhibition (HI) and neuraminidase-inhibition (NI) assays to evaluate the antibodies induced against viral hemagglutinin (HA) and neuraminidase (NA), respectively. While the two vaccines induced similar levels of HI antibodies against SG/15 after the second vaccination, only WPV-vaccinated mice induced significantly higher titers of NI antibodies against the strain. Furthermore, given the significant elevation of NI antibody titers against DH/07, an H5N1 avian influenza virus, WPV was also demonstrated to induce NA-inhibiting antibodies that recognize NA of divergent strains. This could be explained by the higher conservation of epitopes of NA among strains than for HA. Taking these findings together, NA-specific antibodies induced by WPV may have contributed to better protection from infection with heterologous influenza virus SG/15, compared with SV. The present results indicate that WPV is an effective vaccine for inducing antibodies against both HA and NA of heterologous viruses and may be a useful vaccine to conquer vaccine strain mismatch.

A phase 1 dose-sparing, randomized clinical trial of seasonal trivalent inactivated influenza vaccine combined with MAS-1, a novel water-in-oil adjuvant/delivery system

BACKGROUND

New influenza vaccines are needed to increase vaccine efficacy. Adjuvants may allow hemagglutinin (HA) dose-sparing with enhanced immunogenicity. MAS-1 is an investigational low viscosity, free-flowing, water-in-oil emulsion-based adjuvant/delivery system comprised of stable nanoglobular aqueous droplets.

METHODS

A phase 1, double-blind, safety and immunogenicity, HA dose escalation, randomized clinical trial was conducted. MAS-1 adjuvant with 1, 3, 5 or 9 µg per HA derived from licensed seasonal trivalent high dose inactivated influenza vaccine (IIV, Fluzone HD 60 µg per HA) in a 0.3 mL dose were compared to standard dose IIV (Fluzone SD, 15 µg per HA). Safety was measured by reactogenicity, adverse events, and clinical laboratory tests. Serum hemagglutination inhibition (HAI) antibody titers were measured for immunogenicity.

RESULTS

Seventy-two subjects, aged 18-47 years, received one dose of either 0.3 mL adjuvanted vaccine or SD IIV intramuscularly. Common injection site and systemic reactions post-vaccination were mild tenderness, induration, pain, headache, myalgia, malaise and fatigue. All reactions resolved within 14 days post-vaccination. Safety laboratory measures were not different between groups. Geometric mean antibody titers, geometric mean fold increases in antibody titer, seroconversion rates and seroprotection rates against vaccine strains were in general higher and of longer duration (day 85 and 169 visits) with MAS-1-adjuvanted IIV at all doses of HA compared with SD IIV. Adjuvanted vaccine induced higher antibody responses against a limited number of non-study vaccine influenza B and A/H3N2 viruses including ones from subsequent years.

CONCLUSION

MAS-1 adjuvant in a 0.3 mL dose volume provided HA dose-sparing effects without safety concerns and induced higher HAI antibody and seroconversion responses through at least 6 months, demonstrating potential to provide greater vaccine efficacy throughout an influenza season in younger adults. In summary, MAS-1 may provide enhanced, more durable and broader protective immunity compared with non-adjuvanted SD IIV. Clinical Trial Registry: ClinicalTrials.gov # NCT02500680.

MAS-1, a novel water-in-oil adjuvant/delivery system, with reduced seasonal influenza vaccine hemagglutinin dose may enhance potency, durability and cross-reactivity of antibody responses in the elderly

BACKGROUND

Increased influenza vaccine efficacy is needed in the elderly at high-risk for morbidity and mortality due to influenza infection. Adjuvants may allow hemagglutinin (HA) dose-sparing with enhanced immunogenicity. MAS-1 is an investigational water-in-oil emulsion-based adjuvant/delivery system comprised of stable nanoglobular aqueous droplets.

METHODS

A phase 1, randomized, double-blind, safety and immunogenicity, adjuvant dose escalation trial was conducted in persons aged 65 years and older. MAS-1 adjuvant dose volumes at 0.3 mL or 0.5 mL containing 9 µg per HA derived from licensed seasonal trivalent influenza vaccine (IIV, Fluzone HD 60 µg per HA, Sanofi Pasteur) were compared to high dose (HD) IIV (Fluzone HD). Safety was measured by reactogenicity, adverse events, and safety laboratory measures. Immunogenicity was assessed by serum hemagglutination inhibition (HAI) antibody titers.

RESULTS

Forty-five subjects, aged 65-83 years, were randomly assigned to receive 9 µg per HA in 0.3 mL MAS-1 (15 subjects) or HD IIV (15 subjects) followed by groups randomly assigned to receive 9 µg per HA in 0.5 mL MAS-1 (10 subjects) or HD IIV (5 subjects). Injection site tenderness, induration, and pain, and headache, myalgia, malaise and fatigue were common, resolving before day 14 post-vaccination. Clinically significant late-onset injection site reactions occurred in four of ten subjects at the 0.5 mL adjuvant dose. Safety laboratory measures were within acceptable limits. MAS-1-adjuvanted IIV enhanced mean antibody titers, mean-fold increases in antibody titer, and seroconversion rates against vaccine strains for at least 168 days post-vaccination and enhanced cross-reactive antibodies against some non-study vaccine influenza viruses.

CONCLUSION

MAS-1 adjuvant provided HA dose-sparing without safety concerns at the 0.3 mL dose, but the 0.5 mL dose caused late injection site reactions. MAS-1-adjuvanted IIV induced higher HAI antibody responses with prolonged durability including against historical strains, thereby providing greater potential vaccine efficacy in the elderly throughout an influenza season. Clinical Trial Registry: ClinicalTrials.gov # NCT02500680.

Antibodies directed towards neuraminidase restrict influenza virus replication in primary human bronchial epithelial cells

Influenza neuraminidase (NA) is implicated in various aspects of the virus replication cycle and therefore is an attractive target for vaccination and antiviral strategies. Here we investigated the potential for NA-specific antibodies to interfere with A(H1N1)pdm09 replication in primary human airway epithelial (HAE) cells. Mouse polyclonal anti-NA sera and a monoclonal antibody could block initial viral entry into HAE cells as well as egress from the cell surface. NA-specific polyclonal serum also reduced virus replication across multiple rounds of infection. Restriction of virus entry correlated with the ability of the serum or monoclonal antibody to mediate neuraminidase inhibition (NI). Finally, human sera with NI activity against the N1 of A(H1N1)pdm09 could decrease H6N1 virus infection of HAE cells, highlighting the potential contribution of anti-NA antibodies in the control of influenza virus infection in humans.

Sex-specific effects of aging on humoral immune responses to repeated influenza vaccination in older adults

Older adults (≥65 years of age) bear a significant burden of severe disease and mortality associated with influenza, despite relatively high annual vaccination coverage and substantial pre-existing immunity to influenza. To test the hypothesis that host factors, including age and sex, play a role in determining the effect of repeated vaccination and levels of pre-existing humoral immunity to influenza, we evaluated pre- and post-vaccination strain-specific hemagglutination inhibition (HAI) titers in adults over 75 years of age who received a high-dose influenza vaccine in at least four out of six influenza seasons. Pre-vaccination titers, rather than host factors and repeated vaccination were significantly associated with post-vaccination HAI titer outcomes, and displayed an age-by-sex interaction. Pre-vaccination titers to H1N1 remained constant with age. Titers to H3N2 and influenza B viruses decreased substantially with age in males, whereas titers in females remained constant with age. Our findings highlight the importance of pre-existing immunity in this highly vaccinated older adult population and suggest that older males are particularly vulnerable to reduced pre-existing humoral immunity to influenza.

Impact of diabetes status on immunogenicity of trivalent inactivated influenza vaccine in older adults

Individuals with type 2 diabetes mellitus experience high rates of influenza virus infection and complications. We compared the magnitude and duration of serologic response to trivalent influenza vaccine in adults aged 50–80 with and without type 2 diabetes mellitus. Serologic response to influenza vaccination was similar in both groups: greater fold‐increases in antibody titer occurred among participants with lower pre‐vaccination antibody titers. Waning of antibody titers was not influenced by diabetes status.

Association Between Hemagglutination Inhibition Antibody Titers and Protection Against Reverse-Transcription Polymerase Chain Reaction–Confirmed Influenza Illness in Children 6–35 Months of Age: Statistical Evaluation of a Correlate of Protection

Background

Data from a randomized controlled efficacy trial of an inactivated quadrivalent influenza vaccine in children 6–35 months of age were used to determine whether hemagglutination inhibition (HI) antibody titer against A/H1N1 and A/H3N2 is a statistical correlate of protection (CoP) for the risk of reverse-transcription polymerase chain reaction (RT-PCR)–confirmed influenza associated with the corresponding strain.

Methods

The Prentice criteria were used to statistically validate strain-specific HI antibody titer as a CoP. The probability of protection was identified using the Dunning model corresponding to a prespecified probability of protection at an individual level. The group-level protective threshold was identified using the Siber approach, leading to unbiased predicted vaccine efficacy (VE). A case-cohort subsample was used for this exploratory analysis.

Results

Prentice criteria confirmed that HI titer is a statistical CoP for RT-PCR–confirmed influenza. The Dunning model predicted a probability of protection of 49.7% against A/H1N1 influenza and 54.7% against A/H3N2 influenza at an HI antibody titer of 1:40 for the corresponding strain. Higher titers of 1:320 were associated with >80% probability of protection. The Siber method predicted VE of 61.0% at a threshold of 1:80 for A/H1N1 and 46.6% at 1:113 for A/H3N2.

Conclusions

The study validated HI antibody titer as a statistical CoP, by demonstrating that HI titer is correlated with clinical protection against RT-PCR–confirmed influenza associated with the corresponding influenza strain and is predictive of VE in children 6–35 months of age.

Clinical Trials Registration

NCT01439360.

Endoplasmic reticulum stress response and bile acid signatures associate with multi-strain seroresponsiveness during elderly influenza vaccination

The elderly are an important target for influenza vaccination, and the determination of factors that underlie immune responsiveness is clinically valuable. We evaluated the immune and metabolic profiles of 205 elderly Singaporeans administered with Vaxigrip. Despite high seroprotection rates, we observed heterogeneity in the response. We stratified the cohort into complete (CR) or incomplete responders (IR), where IR exhibited signs of accelerated T cell aging. We found a higher upregulation of genes associated with the B-cell endoplasmic-reticulum stress response in CR, where XBP-1 acts as a key upstream regulator. B-cells from IR were incapable of matching the level of XBP-1 upregulation observed in CR after inducing ER stress with tunicamycin in vitro. Metabolic signatures also distinguished CR and IR - as CR presented with a greater diversity of bile acids. Our findings suggest that the ER-stress pathway activation could improve influenza vaccination in the elderly.

Influence of Pre-Season Antibodies against Influenza Virus on Risk of Influenza Infection among Health Care Personnel

BACKGROUND

The association of hemagglutination inhibition (HAI) antibodies with protection from influenza among healthcare personnel (HCP) with occupational exposure to influenza viruses has not been well-described.

METHODS

The Respiratory Protection Effectiveness Clinical Trial was a cluster-randomized, multi-site study that compared medical masks to N95 respirators in preventing viral respiratory infections among HCP in outpatient healthcare settings for 5,180 participant-seasons. Serum HAI antibody titers before each influenza season and influenza virus infection confirmed by polymerase chain reaction were studied over four study years.

RESULTS

In univariate models, the risk of influenza A(H3N2) and B virus infections was associated with HAI titers to each virus, study year, and site. HAI titers were strongly associated with vaccination. Within multivariate models, each log base 2 increase in titer was associated with 15%, 26% and 33-35% reductions in the hazard of influenza A(H3N2), A(H1N1) and B infections, respectively. Best models included pre-season antibody titers and study year, but not other variables.

CONCLUSIONS

HAI titers were associated with protection from influenza among HCP with routine exposure to patients with respiratory illness and influenza season contributed to risk. HCP can be reassured about receiving influenza vaccination to stimulate immunity.

Prevalence of antibodies against seasonal influenza A and B viruses among older adults in rural Thailand: A cross-sectional study

Assessing the seroprevalence of the high-risk individuals against the influenza virus is essential to evaluate the progress of vaccine implementation programs and establish influenza virus interventions. Herein, we identified the pre-existing cross-protection of the circulating seasonal influenza viruses among the older-aged population. A cross-sectional study was performed base on the 176 residual sera samples collected from older adults aged 60 to 95 years without a history of vaccination in rural Thailand in 2015. Sera antibody titers against influenza A and B viruses circulating between 2016 and 2019 were determined by hemagglutination inhibition assay. These findings indicated the low titers of pre-existing antibodies to circulating influenza subtypes and showed age-independent antibody titers among the old adults. Moderate seropositive rates (HAI ≥ 1:40) were observed in influenza A viruses (65.9%A(H3N2), 50.0% for A(H1N1) pdm09), and found comparatively lower rates in influenza B viruses (14% B/Yam2, 21% B/Yam3 and 25% B/Vic). Only 5% of individuals possessed broadly protective antibodies against both seasonal influenza A and B virus in this region. Our findings highlighted the low pre-existing antibodies to circulating influenza strains in the following season observed in older adults. The serological study will help inform policy-makers for health care planning and guide control measures concerning vaccination programs.

Efficacy of the BNT162b2 mRNA COVID-19 vaccine in patients with B-cell non-Hodgkin lymphoma

Patients diagnosed with B-cell non-Hodgkin lymphoma (B-NHL), particularly if recently treated with anti-CD20 antibodies, are at risk of severe COVID-19 disease. Because studies evaluating humoral response to COVID-19 vaccine in these patients are lacking, recommendations regarding vaccination strategy remain unclear. The humoral immune response to BNT162b2 messenger RNA (mRNA) COVID-19 vaccine was evaluated in patients with B-NHL who received 2 vaccine doses 21 days apart and compared with the response in healthy controls. Antibody titer, measured by the Elecsys Anti-SARS-CoV-2S assay, was evaluated 2 to 3 weeks after the second vaccine dose. Patients with B-NHL (n = 149), aggressive B-NHL (a-B-NHL; 47%), or indolent B-NHL (i-B-NHL; 53%) were evaluated. Twenty-eight (19%) were treatment naïve, 37% were actively treated with a rituximab/obinutuzumab (R/Obi)-based induction regimen or R/Obi maintenance, and 44% had last been treated with R/Obi >6 months before vaccination. A seropositive response was achieved in 89%, 7.3%, and 66.7%, respectively, with response rates of 49% in patients with B-NHL vs 98.5% in 65 healthy controls (P < .001). Multivariate analysis revealed that longer time since exposure to R/Obi and absolute lymphocyte count ≥0.9 × 103/μL predicted a positive serological response. Median time to achieve positive serology among anti-CD20 antibody-treated patients was longer in i-B-NHL vs a-B-NHL. The humoral response to BNT162b2 mRNA COVID-19 vaccine is impaired in patients with B-NHL who are undergoing R/Obi treatment. Longer time since exposure to R/Obi is associated with improved response rates to the COVID-19 vaccine. This study is registered at www.clinicaltrials.gov as #NCT04746092.

Clinical efficacy and safety of high dose trivalent influenza vaccine in adults and immunosuppressed populations - A systematic review and meta-analysis

OBJECTIVES

Influenza is associated with significant morbidity and mortality, especially in older and immunocompromised patients. Few data are available on the clinical benefit of high dose trivalent influenza vaccine (TIV). We aimed to assess the clinical efficacy and safety of high dose TIV.

METHODS

We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs), evaluating high dose versus standard dose TIV for prevention of seasonal influenza in adult population. Primary outcome was laboratory-confirmed influenza. Subgroups analyses included older adults and immunocompromised patients.

RESULTS

We included 16 trials, 47,857 patients; 10 included older adults and three immunocompromised patients. Laboratory confirmed influenza was significantly reduced with high dose TIV (relative risk 0.76, 95% confidence interval 0.64 to 0.9). This outcome stemmed mainly from one trial in older adults. Specifically, A(H3N2) laboratory confirmed influenza, but not A(H1N1) or B lineages, was reduced. No difference in mortality or hospitalizations was demonstrated. Immunological response was significantly higher with high dose vaccine. Serious adverse events were significantly less common in the high dose group.

CONCLUSIONS

High dose TIV lowers the rates of laboratory confirmed influenza, mainly A (H3N2), in older adults vs. standard dose. Further studies should address immunocompromised patients and report clinical outcomes.

Reduced Influenza B-Specific Postvaccination Antibody Cross-reactivity in the B/Victoria Lineage-Predominant 2019/20 Season

BACKGROUND

The influenza activity of the 2019/20 season remained high and widespread in the United States with type B viruses predominating the early season. The majority of B viruses characterized belonged to B/Victoria (B/Vic) lineage and contained a triple deletion of amino acid (aa) 162-164 in hemagglutinin (3DEL). These 3DEL viruses are antigenically distinct from B/Colorado/06/2017 (CO/06)-the B/Vic vaccine component of the 2018/19 and 2019/20 seasons representing the viruses with a double deletion of aa 162-163 in hemagglutinin (2DEL).

METHODS

We performed molecular characterization and phylogenetic analysis of circulating B/Vic viruses. We also conducted hemagglutination inhibition (HAI) assay using archived human postvaccination sera collected from healthy subjects administered with different types of 2018/19 or 2019/20 seasonal vaccines. Their HAI cross-reactivity to representative 3DEL viruses was analyzed.

RESULTS

The CO/06-specific human postvaccination sera, after being adjusted for vaccine type, had significantly reduced HAI cross-reactivity toward representative 3DEL viruses, especially the 136E+150K subgroup. The geometric mean titers against 3DEL viruses containing 136E+150K mutations were 1.6-fold lower in all populations (P = .051) and 1.9-fold lower in adults (P = .016) compared with those against the 136E+150N viruses.

CONCLUSIONS

Our results indicate that postvaccination antibodies induced by the B/Vic vaccine component of the 2019/20 influenza season had reduced HAI cross-reactivity toward predominant 3DEL viruses in the United States. A close monitoring of the 3DEL 136E+150K subgroup is warranted should this subgroup return and predominate the 2020/21 influenza season.

A booster dose enhances immunogenicity of the COVID-19 vaccine candidate ChAdOx1 nCoV-19 in aged mice

BACKGROUND

The spread of SARS-CoV-2 has caused a worldwide pandemic that has affected almost every aspect of human life. The development of an effective COVID-19 vaccine could limit the morbidity and mortality caused by infection and may enable the relaxation of social-distancing measures. Age is one of the most significant risk factors for poor health outcomes after SARS-CoV-2 infection; therefore, it is desirable that any new vaccine candidates elicit a robust immune response in older adults.

METHODS

Here, we use in-depth immunophenotyping to characterize the innate and adaptive immune response induced upon intramuscular administration of the adenoviral vectored ChAdOx1 nCoV-19 (AZD-1222) COVID-19 vaccine candidate in mice.

FINDINGS

A single vaccination generates spike-specific Th1 cells, Th1-like Foxp3⁺ regulatory T cells, polyfunctional spike-specific CD8⁺ T cells. and granzyme-B-producing CD8 effectors. Spike-specific IgG and IgM are generated from both the early extrafollicular antibody response and the T follicular helper cell-supported germinal center reaction, which is associated with the production of virus-neutralizing antibodies. A single dose of this vaccine generated a similar type of immune response in aged mice but of a reduced magnitude than in younger mice. We report that a second dose enhances the immune response to this vaccine in aged mice.

CONCLUSIONS

This study shows that ChAdOx1 nCoV-19 induces both cellular and humoral immunity in adult and aged mice and suggests a prime-boost strategy is a rational approach to enhance immunogenicity in older persons.

FUNDING

This study was supported by BBSRC, Lister institute of Preventative Medicine, EPSRC VaxHub, and Innovate UK.

Vaccines for older adults

The proportion of the global population aged 65 and older is rapidly increasing. Infections in this age group, most recently with SARS-CoV-2, cause substantial morbidity and mortality. Major improvements have been made in vaccines for older people, either through the addition of novel adjuvants-as in the new recombinant zoster vaccine and an adjuvanted influenza vaccine-or by increasing antigen concentration, as in influenza vaccines. In this article we review improvements in immunization for the three most important vaccine preventable diseases of aging. The recombinant zoster vaccine has an efficacy of 90% that is minimally affected by the age of the person being vaccinated and persists for more than four years. Increasing antigen dose or inclusion of adjuvant has improved the immunogenicity of influenza vaccines in older adults, although the relative effectiveness of the enhanced influenza vaccines and the durability of the immune response are the focus of ongoing clinical trials. Conjugate and polysaccharide pneumococcal vaccines have similar efficacy against invasive pneumococcal disease and pneumococcal pneumonia caused by vaccine serotypes in older adults. Their relative value varies by setting, depending on the prevalence of vaccine serotypes, largely related to conjugate vaccine coverage in children. Improved efficacy will increase public confidence and uptake of these vaccines. Co-administration of these vaccines is feasible and important for maximal uptake in older people. Development of new vaccine platforms has accelerated following the arrival of SARS-CoV-2, and will likely result in new vaccines against other pathogens in the future.

Immunological surrogate endpoints of COVID-2019 vaccines: the evidence we have versus the evidence we need

In response to the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic, over 200 vaccine candidates against coronavirus disease 2019 (COVID-2019) are under development and currently moving forward at an unparalleled speed. The availability of surrogate endpoints would help to avoid large-scale filed efficacy trials and facilitate the approval of vaccine candidates, which is crucial to control COVID-19 pandemic. Several phase 3 efficacy trials of COVID-19 vaccine candidates are under way, which provide opportunities for the determination of COVID-19 correlates of protection. In this paper, we review current knowledge for existence of COVID-19 correlates of protection, methods for assessment of immune correlates of protection and issues related to COVID-19 correlates of protection.

T Cell Immunity against Influenza: The Long Way from Animal Models Towards a Real-Life Universal Flu Vaccine

Current flu vaccines rely on the induction of strain-specific neutralizing antibodies, which leaves the population vulnerable to drifted seasonal or newly emerged pandemic strains. Therefore, universal flu vaccine approaches that induce broad immunity against conserved parts of influenza have top priority in research. Cross-reactive T cell responses, especially tissue-resident memory T cells in the respiratory tract, provide efficient heterologous immunity, and must therefore be a key component of universal flu vaccines. Here, we review recent findings about T cell-based flu immunity, with an emphasis on tissue-resident memory T cells in the respiratory tract of humans and different animal models. Furthermore, we provide an update on preclinical and clinical studies evaluating T cell-evoking flu vaccines, and discuss the implementation of T cell immunity in real-life vaccine policies.

Efficacy and effectiveness of high-dose influenza vaccine in older adults by circulating strain and antigenic match: An updated systematic review and meta-analysis

BACKGROUND

Influenza vaccine efficacy/effectiveness can vary from season to season due in part to the dominant circulating strains and antigenic matching. This study reviews the relative vaccine efficacy/effectiveness (rVE) of high-dose inactivated trivalent influenza vaccine (HD-IIV3) compared to standard-dose influenza vaccines (SD-IIV) in adults aged ≥ 65 years against influenza-associated outcomes. Additional sub-analyses of HD-IIV3 rVE were performed by the predominantly circulating influenza strain and the antigenic match or mismatch of the vaccine against the predominant circulating strains.

METHODS

An updated systematic review and meta-analysis was conducted for studies assessing the rVE of HD-IIV3 against probable/laboratory-confirmed influenza-like illness (ILI), hospital admissions, and death in adults aged ≥ 65 years. Results from individual seasons were extracted from the studies, and viral surveillance data were used to determine the dominant circulating strains and antigenic match for each season. Results were then stratified based on clinical outcomes and seasonal characteristics and meta-analyzed to estimate pooled rVEs of HD-IIV3.

RESULTS

15 publications were meta-analyzed after screening 1,293 studies, providing data on 10 consecutive influenza seasons and over 22 million individuals receiving HD-IIV3 in randomized and observational settings. Across all influenza seasons, HD-IIV3 demonstrated improved protection against ILI compared to SD-IIV (rVE = 15.9%, 95% CI: 4.1-26.3%). HD-IIV3 was also more effective at preventing hospital admissions from all-causes (rVE = 8.4%, 95% CI: 5.7-11.0%), as well as influenza (rVE = 11.7%, 95% CI: 7.0-16.1%), pneumonia (rVE = 27.3%, 95% CI: 15.3-37.6%), combined pneumonia/influenza (rVE = 13.4%, 95% CI: 7.3-19.2%) and cardiorespiratory events (rVE = 17.9%, 95% CI: 15.0-20.8%). Reductions in mortality due to pneumonia/influenza (rVE = 39.9%, 95% CI: 18.6-55.6%) and cardiorespiratory causes (rVE = 27.7%, 95% CI: 13.2-32.0%) were also observed. Similar pooled rVEs were observed in both matched and mismatched seasons and in seasons where A/H3N2 or A/H1N1 strains were predominantly circulating.

CONCLUSIONS

Evidence over 10 consecutive influenza seasons and in more than 34 million individuals aged ≥ 65 years suggests that HD-IIV3 is consistently more effective than SD-IIV at reducing influenza cases as well as influenza-associated clinical complications irrespective of circulating strain and antigenic match. A video summary of the article can be accessed via the Supplementary data link at the end of this article.

Antibody and Cell-Mediated Immune Responses Are Correlates of Protection against Influenza Infection in Vaccinated Older Adults

Despite efforts to design better vaccines for older adults, the risk for serious complications of influenza remains disproportionately high. Identifying correlates of vaccine effectiveness and understanding the heterogeneity of health outcomes in older adults are key to the vaccine development pipeline. We sought correlates of protection against laboratory-confirmed influenza illness (LCII) in a 4-year randomized trial of standard versus high-dose influenza vaccination of adults 65 years and older. To this end, we quantified serum hemagglutination-inhibition (HAI) titers and interferon-gamma (IFNγ) and interleukin-10 (IL-10) secretion by virus-challenged peripheral blood mononuclear cells. Of the 608 participants included, 26 developed either A/H3N2-(n = 17) or B-LCII (n = 9) at 10-20 weeks post-vaccination. Antibody titres for A/H3N2 at 4-weeks post-vaccination were significantly associated with protection against LCII, where every 1-standard deviation increase reduced the odds of A/H3N2-LCII by 53%. Although B-titres did not correlate with protection against B-LCII, the fold-increase in IFNγ:IL-10 ratios from pre- to 4-weeks post-vaccination was significantly associated with protection against B-LCII, where every 1-standard deviation increase reduced the odds by 71%. Our results suggest that both antibody and cell-mediated immune measures are valuable and potentially complementary correlates of protection against LCII in vaccinated older adults, although this may depend on the viral type causing infection.

Will SARS-CoV-2 Infection Elicit Long-Lasting Protective or Sterilising Immunity? Implications for Vaccine Strategies (2020)

In December 2019, an outbreak of a novel coronavirus (SARS-CoV-2) in Wuhan, China resulted in the current COVID-19 global pandemic. The human immune system has not previously encountered this virus, raising the important question as to whether or not protective immunity is generated by infection. Growing evidence suggests that protective immunity can indeed be acquired post-infection-although a handful of reinfection cases have been reported. However, it is still unknown whether the immune response to SARS-CoV-2 leads to some degree of long-lasting protection against the disease or the infection. This review draws insights from previous knowledge regarding the nature and longevity of immunity to the related virus, SARS-CoV, to fill the gaps in our understanding of the immune response to SARS-CoV-2. Deciphering the immunological characteristics that give rise to protective immunity against SARS-CoV-2 is critical to guiding vaccine development and also predicting the course of the pandemic. Here we discuss the recent evidence that characterises the adaptive immune response against SARS-CoV-2 and its potential implications for the generation of memory responses and long-term protection.

[High-dose trivalent influenza vaccine: safety and immunogenicity]

Las personas mayores son uno de los colectivos que más sufren los efectos de la gripe estacional. Aunque la vacuna antigripal es efectiva a la hora de prevenir la infección por el virus de la gripe y sus complicaciones, no resulta tan efectiva en personas de edad avanzada debido al fenómeno de inmunosenescencia asociado a la edad. Desde 2009 existe en EE. UU. una vacuna antigripal trivalente de alta dosis aprobada para la inmunización de personas ≥ 65 años con una concentración de antígeno cuatro veces mayor que la vacuna estándar. Múltiples ensayos clínicos llevados a cabo a lo largo de distintas temporadas, y mediante diferentes metodologías, han demostrado que la vacuna antigripal trivalente de alta dosis no solo es más efectiva, sino que además presenta un perfil de seguridad similar y es más inmunogénica que la vacuna de dosis estándar en la prevención de la gripe y sus complicaciones en personas de avanzada edad. En este documento se hace una revisión de la evidencia científica actual sobre la seguridad e inmunogenicidad de la vacuna antigripal de alta dosis en personas ≥ 65 años, y se incluye información de ensayos clínicos aleatorizados, estudios observacionales con datos de práctica clínica real y revisiones sistemáticas y metaanálisis.

Immunogenicity of influenza vaccines administered to pregnant women in randomized clinical trials in Mali and South Africa

Background

A key consideration for expanding recommendations for influenza vaccination is a robust assessment of immunogenicity and efficiency of transplacental antibody transfer after maternal vaccination.

Methods

We pooled data from two trials of maternal influenza vaccination to analyze vaccine immunogenicity with more power than either trial had alone. We compared hemagglutination-inhibition (HAI) titers and titer factor change for women and their infants between trial arms using t-tests; maternal and infant putative seroprotective titers (HAI ≥ 1:40) within each trial arm and maternal seroconversion between trial arms using exact tests; and transplacental antibody transfer between trial arms using t-tests. We used marginal linear models and generalized estimating equations to examine the impact of time between maternal vaccination and delivery on transplacental antibody transfer, infant titers, and infant seroprotection.

Results

For all vaccine components (A/H1N1, A/H3N2, and Type B), >80% of vaccinated women had seroprotective titers, >60% of them seroconverted, and >50% of their infants were born with seroprotective titers. These immunogenicity outcomes occurred more often in vaccine recipients and their infants than in controls. No difference in efficiency of transplacental antibody transfer was observed between vaccine recipients and controls.

Conclusions

Our results provide robust support for further expansion of maternal influenza vaccination recommendations.

Clinical Trials Registration: NCT01430689 and NCT01306669.

The Effect of Influenza Vaccination History on Changes in Hemagglutination Inhibition Titers After Receipt of the 2015-2016 Influenza Vaccine in Older Adults in Hong Kong

BACKGROUND

Immune responses to influenza vaccination can be weaker in older adults than in other age groups. We hypothesized that antibody responses would be particularly weak among repeat vaccinees when the current and prior season vaccine components are the same.

METHODS

An observational study was conducted among 827 older adults (aged ≥75 years) in Hong Kong. Serum samples were collected immediately before and 1 month after receipt of the 2015-2016 quadrivalent inactivated influenza vaccine. We measured antibody titers with the hemagglutination inhibition assay and compared the mean fold rise from prevaccination to postvaccination titers and the proportions with postvaccination titers ≥40 or ≥160.

RESULTS

Participants who reported receipt of vaccination during either of the previous 2 years had a lower mean fold rise against all strains than with those who did not. Mean fold rises for A(H3N2) and B/Yamagata were particularly weak after repeated vaccination with the same vaccine strain, but we did not generally find significant differences in the proportions of participants with postvaccination titers ≥40 and ≥160.

CONCLUSIONS

Overall, we found that reduced antibody responses in repeat vaccinees were particularly reduced among older adults who had received vaccination against the same strains in preceding years.

Primary care visits increase utilization of evidence-based preventative health measures

BACKGROUND

Primary care visits can serve many purposes and potentially influence health behaviors. Although previous studies suggest that increasing primary care provider numbers may be beneficial, the mechanism responsible for the association is unclear, and have not linked primary care access to specific preventative interventions. We investigated the association between the number of times patients accessed their primary care provider team and the likelihood they received selected preventative health interventions.

METHODS

Patients with complete data sets from Sanford Health were categorized based on the number of primary care visits they received in a specified time period and the preventative health interventions they received. Patient characteristics were used in a propensity analysis to control for variables. Relative risks and 95% confidence intervals were calculated to estimate the likelihood of obtaining preventative measures based on number of primary care visits compared with patients who had no primary care visits during the specified time period.

RESULTS

The likelihood of a patient receiving three specified preventative interventions was increased by 127% for vaccination, 122% for colonoscopy, and 75% for mammography if the patient had ≥ 1 primary care visit per year. More primary care visits correlated with increasing frequency of vaccinations, but increased primary care visits beyond one did not correlate with increasing frequency of mammography or colonoscopy.

CONCLUSIONS

One or more primary care visits per year is associated with increased likelihood of specific evidence-based preventative care interventions that improve longitudinal health outcomes and decrease healthcare costs. Increasing efforts to track and increase the number of primary care visits by clinics and health systems may improve patient compliance with select preventative measures.

Immunogenicity Measures of Influenza Vaccines: A Study of 1164 Registered Clinical Trials

Influenza carries an enormous burden each year. Annual influenza vaccination is the best means of reducing this burden. To be clinically effective, influenza vaccines must be immunogenic, and several immunological assays to test their immunogenicity have been developed. This study aimed to describe the patterns of use of the various immunological assays available to measure the influenza vaccine-induced adaptive immune response and to determine its correlates of protection. A total of 76.5% of the studies included in our analysis measured only the humoral immune response. Among these, the hemagglutination-inhibition assay was by far the most widely used. Other, less common, humoral immune response assays were: virus neutralization (21.7%), enzyme-linked immunosorbent (10.1%), single radial hemolysis (4.6%), and assays able to quantify anti-neuraminidase antibodies (1.7%). By contrast, cell-mediated immunity was quantified in only 23.5% of studies. Several variables were significantly associated with the use of single assays. Specifically, some influenza vaccine types (e.g., adjuvanted, live attenuated and cell culture-derived or recombinant), study phase and study sponsorship pattern were usually found to be statistically significant predictors. We discuss the principal findings and make some suggestions from the point of view of the various stakeholders.

Distinguishing Causation From Correlation in the Use of Correlates of Protection to Evaluate and Develop Influenza Vaccines

There is increasing attention to the need to identify new immune markers for the evaluation of existing and new influenza vaccines. Immune markers that could predict individual protection against infection and disease, commonly called correlates of protection (CoPs), play an important role in vaccine development and licensing. Here, we discuss the epidemiologic considerations when evaluating immune markers as potential CoPs for influenza vaccines and emphasize the distinction between correlation and causation. While an immune marker that correlates well with protection from infection can be used as a predictor of vaccine efficacy, it should be distinguished from an immune marker that plays a mechanistic role in conferring protection against a clinical endpoint-the latter might be a more reliable predictor of vaccine efficacy and a more appropriate target for rational vaccine design. To clearly distinguish mechanistic and nonmechanistic CoPs, we suggest using the term "correlates of protection" for nonmechanistic CoPs, and ''mediators of protection'' for mechanistic CoPs. Furthermore, because the interactions among and relative importance of correlates or mediators of protection can vary according to age or prior vaccine experience, the effect sizes and thresholds for protective effects for CoPs could also vary in different segments of the population.