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Current influenza vaccines induce immune responses to hemagglutinin (HA), a surface glycoprotein of seasonal influenza viruses, but have suboptimal effectiveness. mRNA vaccines may improve protection by targeting additional antigens such as neuraminidase (NA), for which immune responses independently correlate with protection. In this phase 1/2 trial (NCT05333289), healthy adults 18–75 years were randomly assigned to receive different doses of mRNA-1020 or mRNA-1030 (encoding HA and NA at different ratios), mRNA-1010 (encoding HA), or a licensed active comparator (recombinant HA). Primary endpoints were safety and reactogenicity, and HA and NA antibody responses against vaccine-matched influenza strains. Most common local and systemic solicited ARs were injection site pain and fatigue. There were no vaccine-related serious adverse events nor significant associated safety concerns through 181 days. mRNA-1020 and mRNA-1030 elicited high HA-specific immune responses and induced NA-specific immune responses with no additional reactogenicity at equivalent dose levels beyond an mRNA-based, HA-only–containing vaccine. Improving neuraminidase content of influenza vaccines is a major focus of vaccine development. Here the authors present safety and immunogenicity of seasonal influenza mRNA vaccine candidates simultaneously encoding hemagglutinin and neuraminidase antigens in a first in-human study.

Messenger RNA (mRNA)-based influenza vaccines have the potential to improve upon limitations of current vaccine approaches to seasonal influenza. Here we report findings on the primary and secondary objectives of the safety, reactogenicity, and humoral immunogenicity of the quadrivalent mRNA vaccine, mRNA-1010, versus licensed standard-dose and high-dose quadrivalent influenza vaccines from a three-part, phase 3 clinical trial in adults aged ≥18 years (Part A), 18–64 years (Part B), and ≥ 65 years (Part C) (NCT05827978). A single 50-μg dose of mRNA-1010 elicited hemagglutination inhibition titers against vaccine-matched strains that were statistically noninferior and superior to licensed standard-dose and high-dose egg-based quadrivalent vaccine comparators. Solicited adverse reactions were more frequent with receipt of mRNA-1010; adverse reactions were lower in frequency and severity among adults aged ≥65 years than younger adults. No safety concerns were identified. These findings support the potential benefit of mRNA-1010 as a seasonal influenza vaccine. •Seasonal influenza viral infections are a global health concern.•mRNA platform may improve upon limitations of current influenza vaccine technology.•mRNA-1010 is an mRNA-based vaccine targeting seasonal influenza A and B strains.•mRNA-1010 elicited strong immune responses in adults of all ages.•No safety concerns were identified with mRNA-1010 in this phase 3 study.

Recently, the World Health Organization confirmed 120 new human cases of avian H7N9 influenza in China resulting in 37 deaths, highlighting the concern for a potential pandemic and the need for an effective, safe, and high-speed vaccine production platform. Production speed and scale of mRNA-based vaccines make them ideally suited to impede potential pandemic threats. Here we show that lipid nanoparticle (LNP)-formulated, modified mRNA vaccines, encoding hemagglutinin (HA) proteins of H10N8 (A/Jiangxi-Donghu/346/2013) or H7N9 (A/Anhui/1/2013), generated rapid and robust immune responses in mice, ferrets, and nonhuman primates, as measured by hemagglutination inhibition (HAI) and microneutralization (MN) assays. A single dose of H7N9 mRNA protected mice from a lethal challenge and reduced lung viral titers in ferrets. Interim results from a first-in-human, escalating-dose, phase 1 H10N8 study show very high seroconversion rates, demonstrating robust prophylactic immunity in humans. Adverse events (AEs) were mild or moderate with only a few severe and no serious events. These data show that LNP-formulated, modified mRNA vaccines can induce protective immunogenicity with acceptable tolerability profiles. Potential pandemic influenzas and the need for an effective, safe, and high-speed vaccine production platform have been widely discussed in the scientific community. Bahl et al. report the rapid and robust immune responses achieved against H10N8 and H7N9 viruses from modified mRNA vaccines with an acceptable safety profile.

High-dose inactivated influenza vaccine has been shown to provide protection against influenza that is superior to that with the standard dose. However, data from individually randomized trials on the effectiveness of the high-dose vaccine against severe outcomes are limited. In this pragmatic, open-label, randomized, controlled trial conducted in Denmark during the 2022-2023, 2023-2024, and 2024-2025 influenza seasons, we assigned older adults (≥65 years of age) to receive the high dose of the inactivated influenza vaccine or the standard dose. Data collection relied on nationwide administrative health registries. The primary end point was hospitalization for influenza or pneumonia that occurred from 14 days after vaccination through May 31 of the following year. Of the 332,438 participants who underwent randomization, 166,218 were assigned to receive the high-dose vaccine and 166,220 to receive the standard-dose vaccine. The mean (±SD) age of the participants was 73.7±5.8 years, and 161,538 participants (48.6%) were women. A primary end-point event occurred in 1138 participants (0.68%) in the high-dose group and in 1210 (0.73%) in the standard-dose group (relative vaccine effectiveness, 5.9%; 95.2% confidence interval [CI], -2.1 to 13.4; P = 0.14). Hospitalization for influenza occurred in 0.06% of the participants in the high-dose group and in 0.11% of those in the standard-dose group (relative vaccine effectiveness, 43.6%; 95.2% CI, 27.5 to 56.3); hospitalization for pneumonia occurred in 0.63% and 0.63%, respectively (relative effectiveness, 0.5%; 95.2% CI, -8.6 to 8.8); hospitalization for cardiorespiratory disease in 2.25% and 2.38% (relative effectiveness, 5.7%; 95.2% CI, 1.4 to 9.9); hospitalization for any cause in 9.38% and 9.58% (relative effectiveness, 2.1%; 95.2% CI, -0.1 to 4.3), and death from any cause in 0.67% and 0.66% (relative effectiveness, -2.5%; 95.2% CI, -11.6 to 5.9). The incidence of serious adverse events was similar in the two groups. In this trial, a high-dose inactivated influenza vaccine did not result in a significantly lower incidence of hospitalization for influenza or pneumonia than a standard dose among older adults. (Funded by Sanofi; DANFLU-2 ClinicalTrials.gov number, NCT05517174; EU Clinical Trials Register number, 2022-500657-17-00.).

Several vaccines are approved in the United States for seasonal influenza vaccination every year. Here we compare the impact of repeat influenza vaccination on hemagglutination inhibition (HI) titers, antibody binding and affinity maturation to individual hemagglutinin (HA) domains, HA1 and HA2, across vaccine platforms. Fold change in HI and antibody binding to HA1 trends higher for H1N1pdm09 and H3N2 but not against B strains in groups vaccinated with FluBlok compared with FluCelvax and Fluzone. Antibody-affinity maturation occurs against HA1 domain of H1N1pdm09, H3N2 and B following vaccination with all vaccine platforms, but not against H1N1pdm09-HA2. Importantly, prior year vaccination of subjects receiving repeat vaccinations demonstrated reduced antibody-affinity maturation to HA1 of all three influenza virus strains irrespective of the vaccine platform. This study identifies an important impact of repeat vaccination on antibody-affinity maturation following vaccination, which may contribute to lower vaccine effectiveness of seasonal influenza vaccines in humans Here, Khurana et al. report the results of a phase 4 clinical trial with three FDA approved influenza vaccines and show that repeat influenza vaccination results in reduced antibody affinity maturation to hemagglutinin domain 1 irrespective of vaccine platform.

Improving the efficacy of influenza vaccination in older adults is a challenge. In this randomized clinical trial, a high-dose influenza vaccine was shown to be more effective than a standard-dose vaccine in the prevention of laboratory-confirmed influenza. Between 1990 and 1999, seasonal influenza caused an average of 36,000 deaths and 226,000 hospitalizations per year in the United States. 1 – 3 Adults 65 years of age or older are particularly vulnerable to complications associated with influenza and account for most seasonal influenza–related hospitalizations and deaths. 2 , 3 Although vaccination currently represents the most effective intervention against influenza and associated complications, 3 , 4 antibody response and protection elicited by the vaccine are lower among persons 65 years of age or older than among younger adults. 5 – 7 Strategies to improve antibody responses to influenza vaccine in the older population, such as increasing the . . .

A multicomponent vaccine targeting several seasonal respiratory pathogens may provide simultaneous protection in a single-injection regimen. We present interim (28 days) findings from a phase 1/2 study of an mRNA-based multicomponent vaccine (mRNA-1083), encoding seasonal influenza and SARS-CoV-2 antigens. Adults (18–79 years) were randomly assigned to receive different compositions of mRNA-1083 at varying dose levels on day 1. The primary study objectives were reactogenicity through 7 days and safety through 28 days postvaccination, and the secondary study objective was immunogenicity against vaccine-matched influenza and SARS-CoV-2 strains at day 29 assessed by hemagglutination inhibition and pseudovirus neutralization assays, respectively. The multicomponent mRNA-1083 vaccine was generally well-tolerated, with most solicited adverse reactions being Grade 1 or 2 in severity. The incidence of unsolicited adverse events was similar across vaccine groups. mRNA-1083 induced immune responses against influenza and SARS-CoV-2 that were, in general, similar to or higher than those achieved with licensed quadrivalent influenza (standard or high dose) and SARS-CoV-2 (bivalent mRNA-1273) vaccines. These data support ongoing phase 3 evaluation of the mRNA-1083 vaccine. ClinicalTrials.gov registration: NCT05827926 . An interim analysis shows that a new mRNA influenza and SAR-CoV-2 combination vaccine is safe and triggers an encouraging immune response.

Influenza epidemics cause substantial morbidity. The seasonal vaccine, an important control measure, is not completely efficacious. This trial assessed the efficacy of a recombinant seasonal vaccine (made in a cell culture rather than with viruses grown in eggs). Reducing the burden of influenza disease requires improved vaccines, and a recombinant influenza vaccine may contribute to this public-health goal. 1 This vaccine contains recombinant hemagglutinin (HA) proteins produced in a serum-free medium by expres SF+ cells. These cells contain recombinant baculovirus vectors carrying genes that code for HA. The process yields recombinant HA that is genetically identical to the selected influenza strains without extraneous egg proteins, formaldehyde, antibiotics, or preservatives. Influenza viruses are grown in eggs to produce the inactivated influenza vaccine (IIV); these viruses typically contain mutations in the genes that code for HA that may reduce vaccine effectiveness. . . .

Novel influenza viruses continue to pose a potential pandemic threat worldwide. In recent years, plants have been used to produce recombinant proteins, including subunit vaccines. A subunit influenza vaccine, HAC1, based on recombinant hemagglutinin from the 2009 pandemic A/California/04/2009 (H1N1) strain of influenza virus, has been manufactured using a plant virus-based transient expression technology in Nicotiana benthamiana plants and demonstrated to be immunogenic and safe in pre-clinical studies (Shoji et al., 2011). A first-in-human, Phase 1, single-center, randomized, placebo-controlled, single-blind, dose escalation study was conducted to investigate safety, reactogenicity and immunogenicity of an HAC1 formulation at three escalating dose levels (15μg, 45μg and 90μg) with and without Alhydrogel®, in healthy adults 18–50 years of age (inclusive). Eighty participants were randomized into six study vaccine groups, a saline placebo group and an approved monovalent H1N1 vaccine group. Recipients received two doses of vaccine or placebo (except for the monovalent H1N1 vaccine cohort, which received a single dose of vaccine, later followed by a dose of placebo). The experimental vaccine was safe and well tolerated, and comparable to placebo and the approved monovalent H1N1 vaccine. Pain and tenderness at the injection site were the only local solicited reactions reported following vaccinations. Nearly all adverse events were mild to moderate in severity. The HAC1 vaccine was also immunogenic, with the highest seroconversion rates, based on serum hemagglutination-inhibition and virus microneutralization antibody titers, in the 90μg non-adjuvanted HAC1 vaccine group after the second vaccine dose (78% and 100%, respectively). This is the first study demonstrating the safety and immunogenicity of a plant-produced subunit H1N1 influenza vaccine in healthy adults. The results support further clinical investigation of the HAC1 vaccine as well as demonstrate the feasibility of the plant-based technology for vaccine antigen production.

Self-replicating RNA (srRNA) technology, in comparison to mRNA vaccines, has shown dose-sparing by approximately 10-fold and more durable immune responses. However, no improvements are observed in the adverse events profile. Here, we develop an srRNA vaccine platform with optimized non-coding regions and demonstrate immunogenicity and safety in preclinical and clinical development. Optimized srRNA vaccines generate protective immunity (according to the WHO defined thresholds) at doses up to 1,000,000-fold lower than mRNA in female mouse models of influenza and rabies. Clinically, safety and immunogenicity of RBI-4000, an srRNA vector encoding the rabies glycoprotein, was evaluated in a Phase I study (NCT06048770). RBI-4000 was able to elicit de novo protective immunity in the majority of healthy participants when administered at a dose of 0.1, 1, or 10 microgram (71%, 94%, 100%, respectively) in a prime-boost schedule. Similarly, we observe immunity above the WHO benchmark of protection following a single administration in most participants at both 1 and 10 microgram doses. There are no serious adverse events reported across all cohorts. These data establish the high therapeutic index of optimized srRNA vectors, demonstrating feasibility of both low dose and single dose approaches for vaccine applications. Here the authors report an optimized self-replicating RNA (srRNA) vaccine approach that generates protective immunity at much lower doses than mRNA vaccines in mice. In a Phase 1 study using rabies glycoprotein as antigen, they show robust immune responses at doses as low as 0.1 µg, with a favorable safety profile.