Daniela Cajado-Carvalho, Paulo Newton Tonolli, Verônica de Moraes Manzato, Lívia Mendonça Munhoz Dati, Mahyumi Fujimori, Patrícia Antonia Estima Abreu, Christian Savio Silva, Vitor Anselmo Sakihara, Bianca Pereira Carvalho Holanda, Douglas Gonçalves de Macedo, Priscila Comone, Alexandre Bimbo, Esper George Kallás, Ricardo das Neves Oliveira, Milena Apetito Akamatsu, Paulo Lee Ho
One- and two-vial formulations are viable, stable, and highly immunogenic alternatives for adjuvanted TIV in 2:1 and 1:1 (v/v) formulation ratios (15 µg TIV:IB160). One-vial format simplifies immunization logistics, minimizes operational errors, and is more indicated for routine use, while the two-vial system remains a versatile asset for emergency responses.
BACKGROUND/OBJECTIVES: Adjuvanted influenza vaccines are critical to enhance immune responses in high-risk populations, such as the elderly. While initial studies relied on a two-vial system with antigen and adjuvant mixing prior to immunization, this study evaluated the feasibility, immunogenicity, and 12-month stability of a one-vial formulation combining a Trivalent Influenza Vaccine (TIV) with the locally produced squalene-based oil-in-water emulsion IB160.
METHODS: Formulations were evaluated by testing TIV:IB160 (v/v) ratios (1:1, 2:1, 3:1) in an animal model, measuring HI antibodies as the primary immunogenicity metric, complemented by qualitative strain-specific total IgG screening by ELISA. One-vial and two-vial strategies were also compared regarding immune responses. Formulations stabilities were evaluated at 6.0 °C ± 2.0 °C in one-and two-vial systems by monitoring physicochemical features and their antigenic responses, measuring hemagglutinin content of the formulated vaccines, and long-term HI antibody responses.
RESULTS: The 2:1 and 1:1 (v/v) formulation ratios (15 µg TIV:IB160) induced significantly higher HI titers across all tested strains (A/H3N2/Thailand, A/H1N1/Victoria, and B/Austria) when compared to non-adjuvanted TIV or adjuvanted TIV in the 3:1 ratio. Both the one and two-vial strategies showed significantly higher HI antibody responses than the non-adjuvanted control group (p < 0.05), with no significant differences observed between the delivery formats. Indeed, the one-vial formulation with 1:1 and 2:1 ratios remained stable for 12 months, preserving TIV antigenicity, IB160 emulsion integrity, and robust immunogenicity.
CONCLUSIONS: One- and two-vial formulations are viable, stable, and highly immunogenic alternatives for adjuvanted TIV in 2:1 and 1:1 (v/v) formulation ratios (15 µg TIV:IB160). One-vial format simplifies immunization logistics, minimizes operational errors, and is more indicated for routine use, while the two-vial system remains a versatile asset for emergency responses.