Improving the systemic and mucosal immune response following intranasal vaccination could enhance disease protection against respiratory pathogens. We assessed the safety and immunogenicity of a novel nanoemulsion mucosal adjuvant W₈₀5EC combined with approved seasonal influenza antigens.

This was a first-in-human Phase I study in 199 healthy adult volunteers randomized to receive a single intranasal administration of 5%, 10%, 15% or 20% W₈₀5EC, combined with 4 or 10μg strain-specific Fluzone^® HA, compared with intranasal PBS, intranasal Fluzone^®, or 15 ug strain-specific intramuscular Fluzone^®. Safety was evaluated by physical examination, laboratory parameters, symptom diaries, and adverse event reports. Serum HAI titers and nasal wash IgA were assessed at baseline as well as 28 and 60days after vaccination.

W₈₀5EC adjuvant combined with seasonal influenza antigens was well tolerated without safety concerns or significant adverse events. The highest dose of 20% W₈₀5EC combined with 10μg strain-specific HA elicited clinically meaningful systemic immunity based on increases in serum HAI GMT and ≥70% seroprotection for all 3 influenza strains, as well as a rise in antigen-specific IgA in nasal wash specimens.

W₈₀5EC adjuvant was safe and well tolerated in healthy adult volunteers and elicited both systemic and mucosal immunity following a single intranasal vaccination.