Analyses of Safety Profile and Homologous Antibody Responses to a Mammalian Cell-Based, MF59-Adjuvanted, A/H5N1, Pandemic Influenza Vaccine across Four Phase II/III Clinical Trials in Healthy Children, Adults, and Older Adults

Safety and Immunogenicity of a Carbohydrate Fatty Acid Monosulphate Ester Adjuvant Combined with a Low-Dose Quadrivalent Split-Virion Inactivated Influenza Vaccine: A Randomised, Observer-Blind, Active-Controlled, First-in-Human, Phase 1 Study

Seasonal influenza vaccine effectiveness is low. Carbohydrate fatty acid monosulphate ester (CMS), a new oil-in-water adjuvant, has proven potency in animal models with suggested capacity for dose-sparing. The objective was to evaluate safety and immunogenicity of CMS when added to a low-dose influenza vaccine (QIV) in humans. In a randomised, double-blind, active-controlled, first-in-human study, sixty participants (18-50 years) received either 0.5 mg CMS or 2 mg CMS with 1/5th dose QIV, or a full dose QIV without CMS. Adverse events (AE) were monitored until 7 days post-vaccination. Haemagglutinin inhibition (HI) titres in serum and CD4+ T cells in PBMCs were determined at day 0, 7, 28, and 180. Mean age was 37.6 (±10.1) years and 42/60 (70.0%) were female. Pain at injection site (42/60, 86.7%) and headache (34/60, 56.7%) were reported most and more frequently in the 2 mg CMS group. HI titres and the frequency of influenza specific CD4+ T cells were equal across strains for the three cohorts on all visits, increased until day 28 and decreased at day 180 to values higher than baseline. CMS was safe in humans. Humoral and cell-mediated immunogenicity was similar across vaccines, even with 1/5th antigen dose. CMS can have beneficial implications in low-resource settings or in a pandemic context.

AddaVax-Adjuvanted H5N8 Inactivated Vaccine Induces Robust Humoral Immune Response against Different Clades of H5 Viruses

Since some cases of human infections with H5N8 avian influenza virus have been reported and caused great concern in recent years, it is important to develop an effective vaccine for human use to prevent a potential H5N8 pandemic. In the present study, a vaccine candidate virus based on newly human-infected A/Astrakhan/3212/2020 H5N8 virus was constructed by reverse genetics (RG) technology. The immunogenicity of H5N8 whole virion inactivated vaccine was evaluated by various doses of vaccine antigen formulated with squalene-based adjuvant (AddaVax), aluminum hydroxide (Al(OH)₃) or without adjuvant in mice. The results showed AddaVax-adjuvanted H5N8 inactivated vaccine could stimulate the mice to produce a stronger protective immune response with higher titers of IgG antibodies, hemagglutination inhibition (HI), neuraminidase inhibition (NI) and microneutralization (MN) antibodies than vaccine formulations with Al(OH)₃ adjuvant or without adjuvant, and achieve a dose-sparing effect. Moreover, the AddaVax-adjuvanted formulation also exhibited potent cross-reactive response in HI antibodies against different clades of H5 viruses. A significant correlation and a curve fitting among HI, NI and MN were found by the correlation analysis to predict the protective effect of the vaccine. With these findings, our study demonstrates that AddaVax adjuvant can enhance the immunogenicity of H5N8 inactivated vaccine remarkably, and proposes an effective strategy for dealing with a potential H5N8 virus pandemic.

Phase 3 Randomized, Multicenter, Placebo-Controlled Study to Evaluate Safety, Immunogenicity, and Lot-to-Lot Consistency of an Adjuvanted Cell Culture-Derived, H5N1 Subunit Influenza Virus Vaccine in Healthy Adult Subjects

A cell-based process may be better suited for vaccine production during a highly pathogenic avian influenza (HPAI) pandemic. This was a phase 3, randomized, controlled, observer-blind, multicenter study evaluated safety, immunogenicity, and lot-to-lot consistency of two doses of a MF59-adjuvanted, H5N1 influenza pandemic vaccine manufactured on a cell culture platform (aH5N1c) in 3196 healthy adult subjects, stratified into two age groups: 18 to <65 and ≥65 years. Immunogenicity was measured using hemagglutination inhibition (HI) titers. HI antibody responses increased after the first aH5N1c vaccine dose, and 3 weeks after the second vaccination (Day 43), age-appropriate US Center for Biologics Evaluation and Research (CBER) and former European Medicines Authority Committee for Medicinal Products for Human Use (EMA CHMP) immunogenicity criteria were met. Six months after the first vaccination, HI titers were above baseline but no longer met CBER and CHMP criteria. No relevant changes over time were seen in placebo subjects. Solicited AEs were more frequent in the active treatment than the placebo group, primarily due to injection site pain. No serious adverse events (SAEs) related to aH5N1c- were reported. aH5N1c influenza vaccine elicited high levels of antibodies following two vaccinations administered 21 days apart and met both CBER and former CHMP immunogenicity criteria at Day 43 among both younger and older adults with a clinically acceptable safety profile. Consistency of the three consecutive aH5N1c vaccine lots was demonstrated (NCT02839330).