Standard-dose Influenza Vaccine Research Articles

Relative effectiveness of high-dose versus standard-dose quadrivalent influenza vaccine against hospitalizations and mortality according to frailty score: a post-hoc analysis of the DANFLU-1 trial

Abstract Background Frailty is a major risk factor for adverse cardiovascular events. Influenza vaccination has been shown to protect against cardiovascular fatal and nonfatal events. However, limited data exist on the added benefit of high-dose versus standard-dose influenza vaccination according to frailty status. Purpose We sought to assess the relative effectiveness of high-dose (QIV-HD) versus standard-dose (QIV-SD) quadrivalent influenza vaccination according to frailty status in elderly individuals. Methods This is a post-hoc analysis of the randomized controlled feasibility trial of QIV-HD versus QIV-SD conducted during the 2021–2022 influenza season in adults aged 65–79 years. We assessed the following prespecified outcomes: hospitalizations for pneumonia or influenza, cardio-respiratory hospitalizations, cardiovascular hospitalizations, all-cause hospitalizations and all-cause mortality. Level of frailty was defined according to the Hospital Frailty Risk Score based on ICD-10 codes for relevant comorbidities any time prior to vaccination. We divided the participants into two categories according to Frailty Score (FS): low frailty (0-4 points) and intermediate or high frailty (≥5 points). We analyzed outcomes as time to first event using Cox proportional hazards regression. Results Among 12,473 randomly assigned participants to QIV-HD versus QIV-SD (mean age 71.7 years, 47.1% female), 10,711 (85.9%) were categorized as having low frailty and 1,762 (14.1%) had intermediate or high frailty. In total, 38 individuals were hospitalized for pneumonia or influenza during follow-up, 219 were hospitalized for cardiorespiratory illness, 1055 were hospitalized due to any cause and 62 died during follow-up. FS significantly modified the effect of QIV-HD versus QIV-SD for all-cause mortality (P for interaction 0.02). In participants with low frailty, QIV-HD was associated with a lower risk of all-cause mortality (Figure 1: HR 0.26, 95% CI 0.13 to 0.55), whereas there was no evidence of effect among those with intermediate or high frailty (HR 1.68, 95% CI 0.66 to 4.26). QIV-HD versus QIV-SD was associated with a lower incidence of hospitalizations for pneumonia and influenza, this effect was consistent regardless of frailty status (P for interaction 0.88). QIV-HD was not associated with a significantly lower incidence of hospitalizations due to cardiovascular, cardiorespiratory or respiratory disease or any cause regardless of frailty status. Conclusions In this post-hoc analysis of a large-scale pragmatic trial, QIV-HD was similarly associated with a lower incidence of hospitalizations for pneumonia and influenza among older adults irrespective of frailty status. The potential benefit of QIV-HD versus QIV-SD may therefore be applicable regardless of frailty status. However, our results suggest that QIV-HD is associated with a lower risk of all-cause mortality among adults with low frailty only.Figure 1.

Immunogenicity and Reactogenicity of High-dose or Standard-dose Influenza Vaccine in a Second Consecutive Influenza Season.

Pediatric hematopoietic cell transplant (HCT) recipients are at high-risk for morbidity from influenza virus infection. We demonstrated in a primary phase II randomized controlled trial that two post-HCT doses of high-dose trivalent influenza vaccine (HD-TIV) given four weeks apart were more immunogenic than two doses of standard-dose quadrivalent influenza vaccine (SD-QIV). Herein, we present immunogenicity and safety of influenza vaccination in a consecutive season post-HCT using the same dosing regimen. A subcohort of study participants re-enrolled and had hemagglutinin inhibition (HAI) titers measured at baseline and four weeks after each vaccine dose in year two. We estimated geometric mean fold rise (GMFR) in HAI titer from baseline for each group and used linear mixed effects models to estimate adjusted geometric mean ratios (aGMR, comparing HD-TIV to SD-QIV) for each antigen at each time point. We described systemic and injection-site reactions. A total of 65 subcohort patients participated (33 SD-QIV, 32 HD-TIV). Post-vaccine GMFR and aGMR estimates were higher for both groups following a single influenza vaccine dose in year two compared to two doses of the same formulation in year one. Both groups had similar frequencies of injection-site and systemic reactions. A single dose of HD-TIV or SD-QIV was more immunogenic in year two than two doses of the same formulation in year one. Reactogenicity was comparable between groups. One dose of influenza vaccine may be sufficient after a two-dose schedule in the prior year post-HCT.

High-Dose vs Standard-Dose Influenza Vaccine in Chronic Kidney Disease: A Secondary Analysis of DANFLU-1

High-Dose vs Standard-Dose Influenza Vaccine in Chronic Kidney Disease: A Secondary Analysis of DANFLU-1

Cost-effectiveness of recombinant influenza vaccine compared with standard dose influenza vaccine in adults 18–64 years of age

BackgroundThe Advisory Committee on Immunization Practices (ACIP) uses the Evidence to Recommendations Framework that includes cost-effectiveness analyses (CEA) for determining vaccine recommendations. ACIP’s preference for protecting adults ≥ 65 years is enhanced vaccines, including recombinant influenza vaccine (RIV4), adjuvanted or high dose influenza vaccine. Less is known about the CEA of enhanced vaccines for younger adults. MethodsWe used decision analysis modeling from a societal perspective to determine the cost-effectiveness, measured in quality adjusted life years (QALYs), of RIV4 compared with standard dose quadrivalent influenza vaccine (SD-IIV4) in adults 18–64 years old. Model inputs included 2018–2020 vaccine effectiveness (VE) estimates based on medical record data from a large local health system, 2019–2020 national vaccination and influenza epidemic parameters, with costs and population distributions fitted to the season. ResultsAmong adults ages 18–64 years, RIV4 cost $94,186/QALY gained, compared to SD-IIV4. Among those 50–64 years old, RIV4 was relatively more cost-effective ($61,329/QALY gained). Cost-effectiveness estimates for 18–64-year-olds were sensitive to the absolute difference in VE between SD-IIV4 and RIV4, among other parameters. Use of RIV4 in 18–64-year-olds would result in fewer cases (669,984), outpatient visits (261,293), hospitalizations (20,046) and deaths (1,018) annually. The majority (59 %; 597 of 1018) of the decreases in deaths occurred in the 50–64-year-olds. ConclusionsWhile RIV4 was effective and cost-effective relative to SD-IIV4 for both 50–64-year-old and 18–64-year-old adults, cost-effectiveness was sensitive to small changes in parameters among 18–64-year-olds. Because substantial public health benefits occur with enhanced vaccines, health systems and policy makers may opt for preferential product use in select age/risk groups (e.g., 50–64 year olds) to maximize their cost-benefit ratios.

The relative vaccine effectiveness of high-dose vs standard-dose influenza vaccines in preventing hospitalization and mortality: A meta-analysis of evidence from randomized trials

To summarize current evidence of high-dose influenza vaccine (HD-IV) vs standard-dose (SD-IV) regarding severe clinical outcomes. A prespecified meta-analysis was conducted to assess relative vaccine effectiveness (rVE) of HD-IV vs SD-IV in reducing the rates of (1) pneumonia and influenza (P&I) hospitalization, (2) all hospitalizations, and (3) all-cause death in adults ≥65 years in randomized controlled trials. Pooled effect sizes were estimated using fixed-effects models with the inverse variance method. Five randomized trials were included encompassing 105,685 individuals. HD-IV vs SD-IV reduced P&I hospitalizations (rVE: 23.5%, [95%CI: 12.3 to 33.2]). HD-IV vs SD-IV also reduced rate of all-cause hospitalizations (rVE: 7.3%, [95%CI: 4.5 to 10.0]). No significant differences were observed in death rates (rVE = 1.6% ([95%CI: -2.0 to 5.0]) in HD-IV vs SD-IV. Sensitivity analyses omitting trials with participants sharing the same comorbidity, trials with ≥100 events, and random-effects models provided comparable estimates for all outcomes. HD-IV reduced the incidence of P&I and all-cause hospitalization vs SD-IV in adults ≥65 years in randomized trials, through no significant difference was observed in all-cause death rates. These findings, supported by evidence from several randomized studies, can benefit from replication in a fully powered, individually randomized trial.

Feasibility and Findings of Including Self-Identified Adult Congenital Heart Disease Patients in the INVESTED Trial

BackgroundAdult congenital heart disease (ACHD) patients have significant morbidity and rise in cardiac admissions. Their outcome with high-dose influenza vaccination is unknown in comparison to those without ACHD. ObjectivesThe purpose of this study was to compare all-cause mortality or cardiopulmonary hospitalizations in self-identified ACHD versus non-ACHD patients receiving high- or low-dose influenza vaccination within the INfluenza Vaccine to Effectively Stop cardioThoracic Events and Decompensated heart failure trial. MethodsWe prospectively included ACHD patients in the INVESTED (INfluenza Vaccine to Effectively Stop cardioThoracic Events and Decompensated heart failure) trial. The primary endpoint was all-cause death or hospitalization for cardiovascular or pulmonary causes. ResultsOf the 272 ACHD patients, 132 were randomly assigned to receive high-dose trivalent and 140 to standard-dose quadrivalent influenza vaccine. Compared to the non-ACHD cohort (n = 4,988), ACHD patients were more likely to be younger, women, smokers, have atrial fibrillation, and have a qualifying event of heart failure. The primary outcome was 49.8 events versus 42.8 events per 100 person-years (adjusted HR: 1.17; 95% CI: 0.95-1.45; P = 0.144) in the ACHD group and non-ACHD group, respectively. The interaction between ACHD status and randomized treatment effect was not significant for the primary outcome (P = 0.858). Vaccine-related adverse events were similar in both groups. ConclusionsPatients who self-identify as being ACHD had similar primary outcome of all-cause death or hospitalization for cardiovascular or pulmonary causes compared to non-ACHD cohort. High-dose influenza vaccination was similar to standard-dose influenza vaccination on the primary outcome in patients who self-identify as ACHD.

In-Hospital influenza vaccination to prevent cardiorespiratory events in the first 45 days after acute coronary syndrome: A prespecified analysis of the VIP-ACS trial

BackgroundInfluenza vaccination prevents major cardiovascular events in individuals presenting a recent acute coronary syndrome (ACS), however the early effect of an in-hospital double-dose vaccination strategy remains uncertain. MethodsThe VIP-ACS was a randomized, pragmatic, multicenter, open-label trial with a blinded-adjudication endpoint. Patients with ACS ≤ 7 days of hospitalization were randomized to an in-hospital double-dose quadrivalent inactivated influenza vaccine (double-dose) or a standard-dose influenza vaccine at 30 days post-randomization. The primary endpoint was a hierarchical composite of death, myocardial infarction, stroke, hospitalization for unstable angina, hospitalization for heart failure, urgent coronary revascularization, and hospitalization for respiratory infections, analyzed with the win ratio (WR) method in short-term follow-up (45-days after randomization). ResultsThe trial enrolled 1,801 patients (≥18 years old). Median participant age was 57 years, 70 % were male. There were no significant differences between groups on the primary hierarchical endpoint: there were 5.7 % wins in the double-dose in-hospital group and 5.5 % wins in the standard-dose delayed vaccination group (WR: 1.03; 95 % CI: 0.70–––1.53; P = 0.85). In a sensitivity analysis including COVID-19 infection in the hospitalizations for respiratory infections endpoint, overall results were maintained (WR: 1.03; 95 % CI 0.71–––1.51; P = 0.87). Results were consistent for major cardiovascular events only (WR: 0.82; 95 % CI: 0.48–––1.39; P = 0.46). No serious adverse events were observed. ConclusionIn patients with recent ACS, in-hospital double-dose influenza vaccination did not significantly reduce cardiorespiratory events at 45 days compared with standard-dose vaccination at 30 days post-randomization.

Recombinant or Standard-Dose Influenza Vaccine in Adults under 65 Years of Age

BackgroundQuadrivalent recombinant influenza vaccines contain three times the amount of hemagglutinin protein as standard-dose egg-based vaccines, and the recombinant formulation is not susceptible to antigenic drift during manufacturing. Data are needed on the relative effectiveness of recombinant vaccines as compared with standard-dose vaccines against influenza-related outcomes in adults under the age of 65 years.MethodsIn this cluster-randomized observational study, Kaiser Permanente Northern California facilities routinely administered either a high-dose recombinant influenza vaccine (Flublok Quadrivalent) or one of two standard-dose influenza vaccines during the 2018–2019 and 2019–2020 influenza seasons to adults 50 to 64 years of age (primary age group) and 18 to 49 years of age. Each facility alternated weekly between the two vaccine formulations. The primary outcome was influenza (A or B) confirmed by polymerase-chain-reaction (PCR) testing. Secondary outcomes included influenza A, influenza B, and influenza-related hospitalization outcomes. We used Cox regression analysis to estimate the hazard ratio of the recombinant vaccine as compared with the standard-dose vaccines against each outcome. We calculated the relative vaccine effectiveness as 1 minus the hazard ratio.ResultsThe study population included 1,630,328 vaccinees between the ages of 18 and 64 years (632,962 in the recombinant-vaccine group and 997,366 in the standard-dose group). During this study period, 1386 cases of PCR-confirmed influenza were diagnosed in the recombinant-vaccine group and 2435 cases in the standard-dose group. Among the participants who were 50 to 64 years of age, 559 participants (2.00 cases per 1000) tested positive for influenza in the recombinant-vaccine group as compared with 925 participants (2.34 cases per 1000) in the standard-dose group (relative vaccine effectiveness, 15.3%; 95% confidence interval [CI], 5.9 to 23.8; P=0.002). In the same age group, the relative vaccine effectiveness against influenza A was 15.7% (95% CI, 6.0 to 24.5; P=0.002). The recombinant vaccine was not significantly more protective against influenza-related hospitalization than were the standard-dose vaccines.ConclusionsThe high-dose recombinant vaccine conferred more protection against PCR-confirmed influenza than an egg-based standard-dose vaccine among adults between the ages of 50 and 64 years. (Funded by Sanofi; ClinicalTrials.gov number, NCT03694392.)

Excessive daytime sleepiness is associated with impaired antibody response to influenza vaccination in older male adults.

The reduced effectiveness of standard-dose influenza vaccines in persons ≥65 years of age led to the preferential recommendation to use high-dose (HDFlu) or MF59-adjuvanted (MF59Flu) vaccines for this age group. Sleep is an important modulator of immune responses to vaccines and poor sleep health is common in older adults. However, potential effects of poor sleep health on immune responses to influenza vaccination in older adults remain largely unknown. We conducted a cohort study of 210 healthy participants age ≥65 years, who received either seasonal high-dose (HDFlu) or MF59-adjuvanted (MF59Flu) influenza vaccine. We assessed sleep characteristics in this cohort by standardized questionnaires and measured the antibody titer against influenza A/H3N2 virus in serum of study participants by hemagglutination inhibition assay on the day of immunization and 28 days thereafter. We then assessed the association between sleep characteristics and antibody titers. Our results demonstrated that male, but not female, study participants with excessive daytime sleepiness had an impaired influenza A/H3N2-specific antibody response at Day 28 post-vaccination. No other associations were found between antibody titer and other sleep characteristics, including sleep quality and obstructive sleep apnea. Our results provide an additional and easily measured variable explaining poor vaccine effectiveness in older adults. Our results support that gaining sufficient sleep is a simple non-vaccine interventional approach to improve influenza immune responses in older adults. Our findings extend the literature on the negative influence of excessive daytime sleepiness on immune responses to influenza vaccination in older male adults.

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

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. 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. 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. 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.

High-Dose vs. Standard-Dose Influenza Vaccine and Cardiopulmonary Hospitalization or Mortality: Emulating the INVESTED Trial Using Insurance Claims Data.

The INVESTED trial did not show benefits of high-dose (HD) vaccine vs. standard-dose (SD) for a primary composite outcome of cardiopulmonary hospitalization or all-cause mortality (hazard ratio (HR) = 1.05, 95% confidence interval (CI) = 0.96-1.15) and its components (all-cause mortality HR = 1.01, 95% CI = 0.84-1.21, cardiopulmonary hospitalization HR = 1.05, 95% CI = 0.96-1.16) during three influenza seasons (2016-2019) among participants with recent myocardial infarction or hospitalization for heart failure (HHF). We emulated INVESTED using Medicare claims data to assess whether the real-world evidence (RWE) study reached similar conclusions. We identified 1:1 propensity score (PS)-matched trial-eligible Medicare beneficiaries aged > 65 years and with prior HHF who received an HD or SD vaccine for the 2016-2019 seasons. We also re-analyzed the INVESTED trial data restricting to participants > 65 years with prior HHF to align eligibility criteria more closely with the RWE study. We compared HRs from the trial and RWE study for the main outcomes. Among 53,393 pairs of PS-matched Medicare beneficiaries, the HD vaccine group showed lower risk of the primary composite outcome (HR = 0.96, 95% CI = 0.95-0.98) and all-cause mortality (HR = 0.93, 95% CI = 0.91-0.95), and similar risk of cardiopulmonary hospitalization (HR = 0.98, 95% CI = 0.96-1.00), compared with SD. The RWE and trial results were closely concordant after the trial population was limited to participants > 65 years with prior HHF: trial-based results for the primary composite outcome (HR = 1.02, 95% CI = 0.89-1.17), all-cause mortality (HR = 0.92, 95% CI = 0.72-1.16), and cardiopulmonary hospitalization (HR = 1.02, 95% CI = 0.88-1.18). Although similar to the main trial results, the RWE was closer to the results from trial participants with aligned eligibility criteria. This study affirms the importance of considering different distributions of baseline patient characteristics when comparing trial findings to RWE.

Assessment of Humoral Immune Responses to Repeated Influenza Vaccination in a Multiyear Cohort: A 5-Year Follow-up.

The long-term effects of host factors on vaccine-elicited immune responses have not been well studied, and the interactions of host factors with annual influenza vaccinations are yet to be explored. We analyzed data from a cohort of 386 individuals who received the standard-dose influenza vaccine and enrolled in ≥2 seasons from 2016 to 2020. Our analyses indicated disparate vaccine-elicited immune responses between males and females in adults when they were repeatedly vaccinated for at least 2 seasons. Notably, we found interactive effects between age and body mass index (BMI) on overall immune responses, and between sex at birth and BMI in adults.

Comparison of Two High-Dose Versus Two Standard-Dose Influenza Vaccines in Adult Allogeneic Hematopoietic Cell Transplant Recipients.

Adult hematopoietic cell transplant (HCT) recipients are at high risk for influenza-related morbidity and mortality and have suboptimal influenza vaccine immune responses compared to healthy adults, particularly within 2 years of transplant. This phase II, double-blind, multicenter randomized controlled trial compared 2 doses of high-dose trivalent (HD-TIV) to 2 doses of standard-dose quadrivalent (SD-QIV) influenza vaccine administered 1 month apart in adults 3-23 months post-allogeneic HCT. Hemagglutinin antibody inhibition (HAI) titers were measured at baseline, 4 weeks following each vaccine dose, and approximately 7 months post-second vaccination. Injection-site and systemic reactions were assessed for 7 days post-vaccination. The primary immunogenicity comparison was geometric mean HAI titer (GMT) at visit 3 (4 weeks after the second dose); we used linear mixed models to estimate adjusted GMT ratios (aGMRs) comparing HD-TIV/SD-QIV for each antigen. We randomized 124 adults; 64 received SD-QIV and 60 received HD-TIV. Following the second vaccination, HD-TIV was associated with higher GMTs compared to SD-QIV for A/H3N2 (aGMR = 2.09; 95% confidence interval [CI]: [1.19, 3.68]) and B/Victoria (aGMR = 1.61; 95% CI: [1.00, 2.58]). The increase was not statistically significant for A/H1N1 (aGMR = 1.16; 95% CI: [0.67, 2.02]). There was a trend to more injection-site reactions for HD-TIV after the second vaccination compared to SD-QIV (50% vs 33%; adjusted odds ratio [aOR] = 4.53; 95% CI: [0.71, 28.9]), whereas systemic reactions were similar between groups with both injections. Adult allogeneic HCT recipients who received 2 doses of HD-TIV produced higher HAI antibody responses for A/H3N2 and B/Victoria compared with 2 doses of SD-QIV, with comparable injection-site or systemic reactions.

Vaccine effectiveness of recombinant and standard dose influenza vaccines against influenza related hospitalization using a retrospective test-negative design

BackgroundRelative effectiveness of various vaccine formulations provide important input for vaccine policy decisions and provider purchasing decisions. We used electronic databases to conduct a test-negative case control study to determine relative vaccine effectiveness (rVE) of recombinant influenza vaccine (RIV4) compared with standard dose vaccines (SD-IIV4) against influenza hospitalization. MethodsAdults 18–64 and ≥65 years of age hospitalized in a large U.S. health system (19 hospitals) in 2018–2019 and 2019–2020 who were clinically tested for influenza using reverse transcription polymerase chain reaction (RT-PCR) assays were included. The hospital system electronic medical record (EMR) and the state immunization registry were used to confirm influenza vaccination. Propensity scores with inverse probability weighting were used to adjust for potential confounders and determine rVE. ResultsOf the 14,590 individuals included in the primary analysis, 3,338 were vaccinated with RIV4 and 976 were vaccinated with SD-IIV4, with the balance of 10,276 being unvaccinated. Most participants were white (80 %), most (70 %) had a high-risk condition, just over half were female (54 %) and age 65 years or older (53 %). Overall RIV4 rVE was significant when adjusted for propensity scores with inverse probability weights (rVE = 31; 95 % CI = 11 %, 46 %). Among younger adults (18–64 years-old), overall rVE of RIV4 was significant (rVE = 29; 95 % CI = 4 %, 47 %). ConclusionsOver all adults, both RIV4 and SD-IIV4 were effective against influenza hospitalization, with RIV4 providing better protection compared with SD-IIV4 overall, for females, younger adults, and those with no high-risk conditions.

Vaccinating the German Population Aged 60 Years and Over with a Quadrivalent High-Dose Inactivated Influenza Vaccine Compared to Standard-Dose Vaccines: A Transmission and Budget Impact Model.

In Germany, influenza vaccination is mainly advised for persons aged 60 years and over and individuals with health risks. Since 2021, an inactivated, quadrivalent high-dose influenza vaccine (IIV4-HD) has been recommended for persons aged 60 years and over. The aim of this study was to calculate the impact of vaccinating the German population aged 60 years and over with IIV4-HD compared to standard-dose influenza vaccines (IIV4-SD) with regard to health outcomes and costs. An age-stratified deterministic compartment model was built to simulate the course of influenza infection for the German population in the season 2019/20. Probabilities for health outcomes and cost data were searched from the literature and were used to compare the influenza-related health and economic effects for different scenarios. Perspectives were those of the statutory health insurance and the society. Deterministic sensitivity analyses were conducted. From the statutory health insurance perspective, vaccinating the German population aged 60 years and over with IIV4-HD would have prevented 277,026 infections (-1.1%) with an increase of overall direct costs of €224 million (+40.1%) compared with IIV4-SD. A separate analysis showed that increased vaccination of 75% (World Health Organization recommendation for older age groups) in persons aged 60 years and over using IIV4-SD only would prevent 1,289,648 infections (-5.1%) and would save costs from a statutory health insurance perspective of €103 million (-13.2%) compared with IIV4-HD at actual vaccination rates. The modeling approach offers important insights into the epidemiological and budgetary impact of different vaccination scenarios. Achieving a higher vaccination coverage with IIV4-SD in persons aged 60 years and over would result in lower costs and fewer influenza infections compared with the scenario with IIV4-HD and actual vaccination rates.

High-dose influenza vaccine in older adults by age and seasonal characteristics: Systematic review and meta-analysis update

This updated systematic review and meta-analysis of randomized and observational studies published up to April 2023 assessed the relative performance of high-dose inactivated influenza vaccine (HD-IIV) and standard-dose influenza vaccines (SD-IIV) against influenza-associated outcomes in older adults (≥65 years).The analysis included studies conducted over 12 influenza seasons (2009/2010 to 2019/2020, 2021/2022), including over 45 million individuals aged ≥ 65 years, and showed that HD-IIV provided significantly better protection than SD-IIV against influenza-like illness and influenza-related hospitalizations, as well as cardiovascular, cardiorespiratory, and all-cause hospitalizations. Subgroup analyses showed HD-IIV consistently provided better protection than SD-IIV against influenza outcomes across the age range (65+, 75+ 85+ years), and regardless of the predominantly circulating influenza strain and vaccine antigenic match/mismatch.Randomized studies continue to drive high-quality evidence on the effectiveness of high-dose inactivated influenza vaccine relative to SD-IIV against severe influenza outcomes in adults aged ≥ 65 years, supported by observational data.

High-Dose Influenza Vaccine Is Associated With Reduced Mortality Among Older Adults With Breakthrough Influenza Even When There Is Poor Vaccine-Strain Match.

High-dose (HD) influenza vaccine offers improved protection from influenza virus infection among older adults compared with standard-dose (SD) vaccine. Here, we explored whether HD vaccine attenuates disease severity among older adults with breakthrough influenza. This was a retrospective cohort study of US claims data for influenza seasons 2016-2017, 2017-2018, and 2018-2019, defined as 1 October through 30 April, among adults aged ≥65 years. After adjusting the different cohorts for the probability of vaccination conditional on patients' characteristics, we compared 30-day mortality rate post-influenza among older adults who experienced breakthrough infection after receipt of HD or SD influenza vaccines and among those not vaccinated (NV). We evaluated 44 456 influenza cases: 23 109 (52%) were unvaccinated, 15 037 (33.8%) received HD vaccine, and 6310 (14.2%) received SD vaccine. Significant reductions in mortality rates among breakthrough cases were observed across all 3 seasons for HD vs NV, ranging from 17% to 29% reductions. A significant mortality reduction of 25% was associated with SD vaccination vs NV in the 2016-2017 season when there was a good match between circulating influenza viruses and selected vaccine strains. When comparing HD vs SD cohorts, mortality reductions were higher among those who received HD in the last 2 seasons when mismatch between vaccine strains and circulating H3N2 viruses was documented, albeit not significant. HD vaccination was associated with lower post-influenza mortality among older adults with breakthrough influenza, even during seasons when antigenically drifted H3N2 circulated. Improved understanding of the impact of different vaccines on attenuating disease severity is warranted when assessing vaccine policy recommendations.

Superior immunogenicity of high-dose quadrivalent inactivated influenza vaccine versus Standard-Dose vaccine in Japanese Adults ≥ 60 years of age: Results from a phase III, randomized clinical trial

BackgroundA high-dose, split-virion inactivated quadrivalent influenza vaccine (IIV4-HD; Sanofi) is being used for the prevention of influenza in multiple countries. This study examined the immunogenicity and safety of the IIV4-HD vaccine administered intramuscularly (IM) compared with a locally licensed standard-dose influenza vaccine (IIV4-SD) administered subcutaneously (SC) in Japan. MethodsThis was a phase III, randomized, modified double-blind, active-controlled, multi-center study in older adults ≥ 60 years of age conducted during the Northern Hemisphere (NH) influenza season of 2020–21 in Japan. Participants were randomized in a 1:1 ratio to receive a single IM injection of IIV4-HD or SC injection of IIV4-SD. Hemagglutination inhibition antibody and seroconversion rates were measured at baseline and day 28. Solicited reactions were collected for up to 7 days after vaccination, unsolicited adverse events up to 28 days after vaccination, and serious adverse events throughout the study. ResultsThe study included 2100 adults ≥ 60 years of age. IIV4-HD given IM induced superior immune responses versus IIV4-SD given SC as assessed by geometric mean titers for all four influenza strains. Superior seroconversion rates were also observed for IIV4-HD compared to IIV4-SD for all influenza strains. The safety profiles of IIV4-HD and IIV4-SD were similar. IIV4-HD was well tolerated in participants, with no safety concerns identified. ConclusionsIIV4-HD provided superior immunogenicity versus IIV4-SD and was well tolerated in participants ≥ 60 years of age in Japan. With superior immunogenicity based on the multiple randomized controlled trials and real-world evidence of trivalent high-dose formulation, IIV4-HD is expected to be the first differentiated influenza vaccine in Japan that offer a greater protection against influenza and its complications in adults 60 years of age and older. Study registrationNCT04498832 (clinicaltrials.gov); U1111-1225–1085 (who.int).

Vaccine effectiveness of recombinant and standard dose influenza vaccines against outpatient illness during 2018–2019 and 2019–2020 calculated using a retrospective test-negative design

ABSTRACT Newer influenza vaccine formulations have entered the market, but real-world effectiveness studies are not widely conducted until there is sufficient uptake. We conducted a retrospective test-negative case-control study to determine relative vaccine effectiveness (rVE) of recombinant influenza vaccine or RIV4, compared with standard dose vaccines (SD) in a health system with significant RIV4 uptake. Using the electronic medical record (EMR) and the Pennsylvania state immunization registry to confirm influenza vaccination, VE against outpatient medically attended visits was calculated. Immunocompetent outpatients ages 18–64 years seen in hospital-based clinics or emergency departments who were tested for influenza using reverse transcription polymerase chain reaction (RT-PCR) assays during the 2018–2019 and 2019–2020 influenza seasons were included. Propensity scores with inverse probability weighting were used to adjust for potential confounders and determine rVE. Among this mostly white and female cohort of 5,515 individuals, 510 were vaccinated with RIV4 and 557 were vaccinated with SD, with the balance of 4,448 (81%) being unvaccinated. Adjusted influenza VE estimates were 37% overall (95% CI = 27, 46), 40% (95% CI = 25, 51) for RIV4 and 35% (95% CI = 20, 47) for standard dose vaccines. Overall, rVE of RIV4 compared to SD was not significantly higher (11%; 95% CI = −20, 33). Influenza vaccines were moderately protective against medically attended outpatient influenza during the 2018–2019 and 2019–2020 seasons. Although the point estimates are higher for RIV4, the large confidence intervals around VE estimates suggest this study was underpowered to detect significant rVE of individual vaccine formulations.

102. Efficacy and Effectiveness of High-Dose Influenza Vaccine in Older Adults by Age and Seasonal Characteristics: An Updated Systematic Review and Meta-Analysis

Abstract Background High-dose influenza vaccine (HD-IIV) has been used extensively in older adults since its approval in 2009. Studies comparing HD-IIV to standard-dose influenza vaccines (SD-IIV) have demonstrated protection beyond influenza, including reduction of outcomes like cardiorespiratory and all-cause hospitalizations. This study is an update of previously-conducted reviews of the relative vaccine efficacy/effectiveness (rVE) of HD-IIV vs. SD-IIV in adults ≥65 years against influenza-associated outcomes from 2009-2020, with sub-analyses by seasonal and recipient characteristics. Methods An updated systematic review and meta-analysis was conducted for studies assessing the rVE of HD-IIV against probable/laboratory-confirmed influenza-like illness (ILI), emergency department (ED) and/or hospital admissions in adults ≥65 years. Results from individual seasons – stratified by outcome, subject characteristics, and influenza season, were meta-analyzed to estimate pooled rVEs of HD-IIV. Results 19 studies from 11 consecutive seasons with over 45 million HD-IIV or SD-IIV recipients were meta-analyzed. Overall, HD-IIV demonstrated improved protection vs. SD-IIV against ILI (rVE=14.3%, 95%CI:4.2-23.3%), HD-IIV was more effective at preventing hospital/ED visits due to influenza (rVE=10.4%, 95%CI:6.8-13.9%), and hospitalizations due to influenza (rVE=11.2%, 95%CI:7.4-14.8%), pneumonia (rVE=27.3%, 95%CI:15.3-37.6%); pneumonia and influenza (rVE=13.4%, 95%CI:7.3-19.2%); respiratory (rVE=14.3%, 95%CI:8.5-20.0%), cardiovascular (rVE=13.1%, 95%CI:10.5-15.7%), and cardiorespiratory events (rVE=17.9%, 95%CI:15.0-20.8%); and all-causes (rVE=8.4%, 95%CI:5.7-11.0%). Pooled rVEs were similar in sub-analyses by dominant strain, antigenic match, and study type/setting. While all adults 65+ benefited from the use of HD-IIV, age-stratified analyses of the rVE of HD-IIV suggested additional relative benefit with increasing age. Conclusion Evidence over 11 consecutive influenza seasons from both randomized and observational studies suggests HD-IIV was consistently more effective than SD-IIV at reducing influenza and associated serious outcomes irrespective of recipient age and characteristics of the influenza season. Disclosures Jason K. Lee, MS, MBiotech, Sanofi: Employee|Sanofi: Stocks/Bonds Gary K. Lam, PharmD, RPh, Sanofi: Employee Rolan Vaisman, PharmD, RPh, Sanofi: Employee Kevin J. Yin, MD, MPH, PhD, Sanofi: Employee|Sanofi: Stocks/Bonds Bruce T. Seet, PhD, MBA, Sanofi: Employee|Sanofi: Stocks/Bonds Matthew M. Loiacono, PhD, MSc, Sanofi: Employee|Sanofi: Stocks/Bonds Sandrine I. Samson, PhD, Sanofi: Employee|Sanofi: Stocks/Bonds.