Safety and Immunogenicity of MF59-Adjuvanted Cell Culture-Derived A/H5N1 Subunit Influenza Virus Vaccine: Dose-Finding Clinical Trials in Adults and the Elderly

Pandemic preparedness through vaccine development for avian influenza viruses

Influenza A viruses pose a significant threat to global health, impacting both humans and animals. Zoonotic transmission, particularly from swine and avian species, is the primary source of human influenza outbreaks. Notably, avian influenza viruses of the H5N1, H7N9, and H9N2 subtypes are of pandemic concern through their global spread and sporadic human infections. Preventing and controlling these viruses is critical due to their high threat level. Vaccination remains the most effective strategy for influenza prevention and control in humans, despite varying vaccine efficacy across strains. This review focuses specifically on pandemic preparedness for avian influenza viruses. We delve into vaccines tested in animal models and summarize clinical trials conducted on H5N1, H7N9, and H9N2 vaccines in humans.

Safety, Tolerability, and Immunogenicity of aH5N1 Vaccine in Adults with and without Underlying Medical Conditions

Influenza pandemics pose a serious risk to the global population, with the potential for high morbidity and mortality. An adjuvanted H5N1 vaccine (aH5N1) has been approved for prophylaxis against the avian influenza virus H5N1, which is a likely cause of future pandemics. In this phase-III, stratified, randomized, controlled, observer-blind, multicenter study, we evaluated the safety and immunogenicity of aH5N1 in four separate groups of adults: adults 18-60 years of age who were healthy or had high-risk medical conditions and older adults ≥61 years of age who were healthy or had high-risk medical conditions. Subjects were randomly assigned to aH5N1 or the comparator, adjuvanted trivalent seasonal influenza vaccine (aTIV). Antibody responses to aH5N1 were increased in all four subgroups and, within each age stratum, largely consistent between healthy subjects and those with medical conditions. Injection-site pain was reported by 66-73% of younger and 36-42% of older-aH5N1 recipients, and fatigue and myalgia were reported by 22-41% of subjects across age and health subgroups. No serious adverse events or deaths were considered related to the study vaccine. In conclusion, aH5N1 increased antibody responses regardless of age or health status and demonstrated a clinically acceptable safety and tolerability profile.

mRNA-Based Vaccines and Therapeutics for COVID-19 and Future Pandemics

An unheard mobilization of resources to find SARS-CoV-2 vaccines and therapies has been sparked by the COVID-19 pandemic. Two years ago, COVID-19's launch propelled mRNA-based technologies into the public eye. Knowledge gained from mRNA technology used to combat COVID-19 is assisting in the creation of treatments and vaccines to treat existing illnesses and may avert pandemics in the future. Exploiting the capacity of mRNA to create therapeutic proteins to impede or treat a variety of illnesses, including cancer, is the main goal of the quickly developing, highly multidisciplinary field of biomedicine. In this review, we explore the potential of mRNA as a vaccine and therapeutic using current research findings.

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

Modern cell culture-based technology eliminates vaccine manufactures reliance on embryonated chicken eggs, which may become compromised during an avian influenza pandemic. Four studies (total N = 6230) assessed the immunogenicity and safety of mammalian cell-based, MF59^®-adjuvanted, A/H5N1 vaccine (aH5N1c; AUDENZ™) as two doses administered on Days 1 and 22 in children (NCT01776554), adults (NCT01776541; NCT02839330), and older adults (NCT01766921; NCT02839330). Immunogenicity of formulations at 7.5 μg and 3.75 μg antigen per dose were assessed by hemagglutination inhibition and microneutralization assays on Days 1, 22, 43, and 183 or 387. Solicited local and systemic adverse events (AEs) were recorded for 7 days after each vaccination. Unsolicited AEs were collected for 21 days after each vaccination, and serious and other selected AEs were recorded for one year. Antibody responses after two 7.5 μg doses met CBER licensure criteria in all age groups. Overall, an age-related response was evident, with the highest responses observed in children <3 years old. In children, antibody titers met seroconversion criteria 12 months after vaccination. MF59 allowed for antigen dose sparing. Solicited AEs were mild to moderate in nature, of short duration, and less frequent after the second dose than the first, demonstrating a favorable risk-benefit profile.

Long-lasting heterologous antibody responses after sequential vaccination with A/Indonesia/5/2005 and A/Vietnam/1203/2004 pre-pandemic influenza A(H5N1) virus vaccines

BACKGROUND

Avian influenza A(H5N1) viruses have caused sporadic infections in humans and thus they pose a significant global health threat. Among symptomatic patients the case fatality rate has been ca. 50%. H5N1 viruses exist in multiple clades and subclades and several candidate vaccines have been developed to prevent A(H5N1) infection as a principal measure for preventing the disease.

METHODS

Serum antibodies against various influenza A(H5N1) clade viruses were measured in adults by ELISA-based microneutralization and haemagglutination inhibition tests before and after vaccination with two different A(H5N1) vaccines in 2009 and 2011.

RESULTS

Two doses of AS03-adjuvanted A/Indonesia/5/2005 vaccine induced good homologous but poor heterologous neutralizing antibody responses against different clade viruses. However, non-adjuvanted A/Vietnam/1203/2004 booster vaccination in 2011 induced very strong and long-lasting homologous and heterologous antibody responses while homologous response remained weak in naïve subjects.

CONCLUSIONS

Sequential vaccination with two different A(H5N1) pre-pandemic vaccines induced long-lasting high level cross-clade immunity against influenza A(H5N1) strains, thus supporting a prime-boost vaccination strategy in pandemic preparedness plans.

Immunogenicity of H5N1 influenza vaccines in elderly adults: a systematic review and meta-analysis

Several different vaccines have been produced for human use to prevent the highly pathogenic H5N1 influenza. Some studies reported that the clinical effectiveness of influenza vaccines in older adults may be lower than in younger adults. In this study, a meta-analysis of the immunogenicity of H5N1 influenza vaccines in elderly adults was performed. Database search was conducted in EMBASE, PubMed, the Cochrane Library, Chinese VIP, Wanfang and CBM. A total of 3951 elderly adults from 10 articles were included in the meta-analysis. Compared to a single dose, two doses of H5N1 vaccines resulted in the higher seroconversion and seroprotection. For all groups treated with adjuvanted vaccines, there were significant increases (1.55- to 2.16-fold) in the seroconversion rates (SCRs) and seroprotection rates (SPRs) after two immunizations. Oil-in-water emulsion (OE)-adjuvanted 7.5 μg vaccine caused higher antibody responses than 3.75 μg of vaccine (SCR: risk ratio (RR) = 1.26 (1.19, 1.33); SPR: RR = 1.25 (1.14, 1.36)). Elderly adults exhibited slightly lower antibody responses only when given 7.5 μg of OE-adjuvanted vaccine (SCR: RR = 1.06 (1.01, 1.11)) than younger adults. After treatment with the 7.5 μg of OE-adjuvanted vaccines, the most commonly reported adverse events were injection site pain, swelling and erythema, with the incidence of 32%, 3% and 2%, respectively, and no serious adverse events were found. These data demonstrate that two doses of 7.5 µg of OE-adjuvanted H5N1 vaccine are well tolerated and induce a robust antibody response in elderly adults.

Registered Interventional Clinical Trials for Old Populations With Infectious Diseases on ClinicalTrials.gov: A Cross-Sectional Study

Background

Interventional clinical trials for infectious diseases in old population have arisen much attention in recent years, however, little is known about the characteristics of registered clinical trials regarding this field. This study aimed to investigate the characteristics of registered interventional trials for infectious diseases in old populations on ClinicalTrials.gov.

Methods

A cross-sectional study was performed. We used viral OR bacterial OR fungal OR parasitic OR infectious disease to search the ClinicalTrials.gov database and to assess characteristics of included trials. The age of participants was restricted to more than 65 years old. All analyses were performed using the SPSS19.0 software.

Results

A total of 138 registered trials were included. Among them, 105(76.1%) trials were completed; however, the results were available in ClinicalTrials.gov for only 44(31.9%) trials. North America was the most frequently identified study location (52.9%), followed by Europe (30.4%) and Asia (11.6%). Seventy-one percent trials focused on viral pathogens, followed by bacterial pathogens (22.5%). A total of 84.1% trials were prevention oriented. A total of 84.1% trials used randomization, 73.2% trials used parallel assignment, and 64.5% used masking. Eighty-six trials were industry-funded and 52 were non-industry-funded. Industry-funded trials had higher percentages than non-industry-funded trials in available results, prevention trial, and phase 2 and phase 3 trial, and lager sample size trial. One hundred eleven trials were vaccine trials and 27 trials were non-vaccine trials. Vaccine trials had higher percentages than non-vaccine trials in available results, leading industry sponsor and viral etiology.

Conclusions

The current study is the first study of the landscape of interventional clinical trials for infectious diseases in old populations registered in ClinicalTrials.gov, providing the basis for treatment and prevention of infectious diseases in old populations. Trials in this field are still relatively lacking, and additional and better trials are needed.

Innate immunemodulator containing adjuvant formulated HA based vaccine protects mice from lethal infection of highly pathogenic avian influenza H5N1 virus

The highly pathogenic avian influenza (HPAI) H5N1 viruses and their spillover into the human population pose substantial economic and public health threats. Although antiviral drugs have some effect in treating influenza infection, vaccination is still the most effective intervention to prevent possible pandemic outbreaks. We have developed a novel H5 influenza vaccine to improve the world's pandemic preparedness. We produced a hemagglutinin (HA) of HPAI H5N1 virus A/Alberta/01/2014 (AB14) using both mammalian (m) and bacterial (b) expression systems. The purified recombinant proteins were formulated with a proprietary adjuvant (TriAdj) and their efficacy as vaccine candidates was evaluated in mice. Intramuscular delivery of two doses of TriAdj formulated mammalian expressed HA (m-HA/TriAdj) was shown to provide full protection against a lethal challenge of AB14 in mice. In contrast, bacterially expressed HA with TriAdj (b-HA/TriAdj), b-HA without adjuvant, and m-HA without adjuvant resulted in no protection in immunized mice. Furthermore, m-HA/TriAdj elicited significantly higher levels of balanced Th1 and Th2 responses and neutralizing antibody titres. All the mice in the m-HA/TriAdj group survived a lethal AB14 H5N1 challenge and showed no signs of disease or infection as demonstrated by no loss of body weight or detectable virus in the lungs. Our results suggest that m-HA formulated with TriAdj has potential to protect against pandemic H5N1 in the event of its cross over to the human host.