Comparison of Adjuvant Potency of Alum, AddaVax, and ISA 71 VG on the Seasonal Split Influenza Vaccine in Mice

Influenza is a highly contagious disease and is transmitted by the upper respiratory tract. Vaccination is an effective strategy to prevent and control seasonal influenza. The current predominant split-inactivated influenza vaccine presents a high safety profile but has weak immunogenicity. The addition of adjuvants is one method to optimize the immunogenicity of the seasonal influenza vaccine. In this study, we compared the effect of aluminum (Alum), MF59-like adjuvant AddaVax, and ISA71 VG adjuvants for the seasonal split influenza vaccine in a mouse model based on the induction of influenza-virus-specific antibody levels, body weight changes, and survival rates after lethal challenge. Two very low and sub-optimal HA doses, 0.003 µg and 0.01 µg, representing the calculated amount of HA from the A/California/07/2009 (H1N1) strain only per mouse dose, were selected and used in this study. The 0.003 µg antigen (Ag) plus AddaVax showed the best adjuvant effect among these three adjuvants. The 0.01 µg Ag plus ISA 71 VG induced the highest total IgG, IgG1, and IgG2a. Both the 0.003 µg and 0.01 µg Ag plus AddaVax protected all the immunized mice from the lethal challenge, and Alum exhibited the protective potency intermediate between that of the AddaVax and ISA 71VG. The 0.01 µg Ag plus one of these three adjuvants could enhance the efficacy of the split influenza vaccine against lethal challenge. Therefore, AddaVax is the first candidate for the further development of the adjuvanted split seasonal influenza vaccine among these three adjuvants. These initial findings offer valuable guidance for selecting promising adjuvanted influenza vaccine formulations.