Intranasal influenza vaccine spurs strong immune response in Phase I study

A new report in the Journal of Clinical Investigation indicates that an experimental single-dose, intranasal influenza vaccine was safe and led to a stable immune response when tested in a Phase I study. The investigational vaccine, called Ad4-H5-VTN, is a recombinant, replicating adenovirus vaccine intended to precipitate antibodies to hemagglutinin, a protein found on the surface of influenza viruses. Developed by Gaithersburg, MD-based Emergent Biosolutions Inc, the vaccine was administered intranasally to 28 participants, as an oral capsule to 10 participants, and through a tonsillar swab to 25 participants, all healthy men and non-pregnant women aged 18-49 years. The participants who received the vaccine intranasally or via tonsillar swab showed significantly higher H5-specific neutralizing antibody levels compared with the group receiving the vaccine capsule. The participants who received the intranasal vaccine shed viral DNA for 2-4 weeks, but the virus could be cultured for a median of only 1 day. Participants had evidence of H5-specific CD4+ and CD8+ T-cell responses. Volunteers who received the intranasal vaccine had high levels of serum neutralizing antibodies at 26 weeks after vaccination; this level was unchanged at 3-5 years after a single intranasal dose of the vaccine. The study authors suggest that replication-competent vector vaccines may be able to express viral proteins at higher levels and for longer durations while also inducing a mucosal immune response.