Assessment of antigen-specific and cross-reactive antibody responses to an MF59-adjuvanted A/H5N1 prepandemic influenza vaccine in adult and elderly subjects.

Preparedness against an A/H5N1 influenza pandemic requires well-tolerated, effective vaccines which provide both vaccine strain-specific and heterologous, cross-clade protection. This study was conducted to assess the immunogenicity and safety profile of an MF59-adjuvanted, prepandemic influenza vaccine containing A/turkey/Turkey/01/2005 (H5N1) strain viral antigen. A total of 343 participants, 194 adults (18 to 60 years) and 149 elderly individuals (≥61 years), received two doses of the investigational vaccine given 3 weeks apart. Homologous and heterologous antibody responses were analyzed by hemagglutination inhibition (HI), single radial hemolysis (SRH), and microneutralization (MN) assays 3 weeks after administration of the first vaccine dose and 3 weeks and 6 months after the second dose. Immunogenicity was assessed according to European licensure criteria for pandemic influenza vaccines. After two vaccine doses, all three European licensure criteria were met for adult and elderly subjects against the homologous vaccine strain, A/turkey/Turkey/1/2005, when analyzed by HI and SRH assays. Cross-reactive antibody responses were observed by HI and SRH analyses against the heterologous H5N1 strains, A/Indonesia/5/2005 and A/Vietnam/1194/2004, in adult and elderly subjects. Solicited local and systemic reactions were mostly mild to moderate in severity and occurred less frequently in the elderly than in adult vaccinees. In both adult and elderly subjects, MF59-adjuvanted vaccine containing 7.5 µg of A/Turkey strain influenza virus antigen was highly immunogenic, well tolerated, and able to elicit cross-clade, heterologous antibody responses against A/Indonesia and A/Vietnam strains 6 weeks after the first vaccination.

Dose-range study of MF59-adjuvanted versus nonadjuvanted monovalent A/H1N1 pandemic influenza vaccine in six- to less than thirty-six-month-old children.

BACKGROUND: The successful vaccination of children 6 to 36 months of age against 2009 A/H1N1 influenza was essential to help reduce the burden of pandemic disease in both the pediatric and adult populations. OBJECTIVES: We compared the immunogenicity and safety of 4 alternative monovalent vaccine formulations to identify which provided optimal levels of seroprotection according to the US and European Union (EU) licensure criteria. SUBJECTS AND METHODS: A total of 654 healthy subjects (6 to <36 months old) were given 2 vaccine doses 3 weeks apart. Participants were assigned to 1 of the 4 immunization groups, receiving MF59-adjuvanted (Novartis Vaccines, Marburg, Germany) vaccine either containing 3.75 µg or 7.5 µg of A/H1N1 California/7/2009 antigen, or nonadjuvanted vaccine containing 7.5 µg or 15 µg of antigen. Antibody titers were assessed by hemagglutination inhibition assay 3 weeks, 3 months and 1 year after immunization. Vaccine safety was monitored throughout the study. RESULTS: After 1 dose, both adjuvanted formulations met the US and EU criteria for seroconversion; the 15 µg nonadjuvanted vaccine met the EU criterion for seroconversion alone. The US and EU criteria for seroprotection were only met by adjuvanted groups. MF59-adjuvanted formulations alone resulted in clinically significant persisting antibody titers after 12 months. All vaccines were well tolerated. CONCLUSIONS: A single dose of MF59-adjuvanted vaccine containing 3.75 µg A/H1N1 antigen was highly immunogenic, met both the US and EU licensure criteria and was well tolerated. These data support the suitability of this monovalent vaccine formulation for pandemic use in children 6 to <36 months of age.

Safety and immunogenicity of an MF59(®)-adjuvanted A/H5N1 pre-pandemic influenza vaccine in adults and the elderly.

BACKGROUND: The potential consequences of an avian influenza pandemic warrants the development of safe, highly immunogenic pre-pandemic A/H5N1 vaccines with cross-clade protection. In this randomized, controlled study we compared the immunogenicity and safety of an MF59(®)-adjuvanted (Novartis Vaccines, Marburg, Germany) A/H5N1 pre-pandemic vaccine with that of a licensed, MF59-adjuvanted, seasonal influenza vaccine. METHODS: Healthy adult (18-60 years, n=3372) and elderly (≥61 years, n=275) volunteers received either an initial dose of a licensed, non-adjuvanted, trivalent, seasonal influenza vaccine (Agrippal(®)) on Day 1, followed by one dose of MF59-H5N1 study vaccine on Day 22 and a second dose of MF59-H5N1 on Day 43, or alternatively, placebo on Day 1 followed by one dose of MF59-adjuvanted seasonal reference vaccine on Day 22 and a second dose of reference vaccine on Day 43. Homologous and cross-reactive A/H5N1 antibody responses were analysed by haemagglutination inhibition (HI), single radial haemolysis (SRH), and microneutralization (MN) assays three weeks after each vaccination. Vaccine safety was assessed throughout the study. RESULTS: Analysis by HI assay found that two doses of MF59-H5N1 resulted in a seroconversion rate of 56% and a geometric mean ratio (GMR) of 7.1 in adult subjects. Similar results were observed on analysis by SRH (GMR 4.03; seroconversion 78% and seroprotection 91%) and MN (seroconversion 67%) assays. These data met the European licensure criteria for influenza vaccines. No significant difference in immunogenicity was detected between the adult and elderly populations. Anti-A/H5N1 cross-clade antibodies were detected by SRH, 49% of adult and 32% of elderly subjects achieved seroconversion after the second vaccine dose. Overall, MF59-H5N1 containing 7.5µg antigen was less reactogenic than the MF59-adjuvanted trivalent seasonal vaccine which contained 15µg antigen for each component strain. CONCLUSIONS: Two doses of MF59-H5N1 vaccine were well tolerated and induced adequate levels of seroprotection against homologous and cross-clade A/H5N1 virus. These data support the suitability of MF59-adjuvanted A/H5N1 vaccine for pre-pandemic use in adults and the elderly.