Abstract: A nasal vaccine is provided which induces the production of secretory IgA and IgG antibodies specific for flaviviruses, including hantaviruses. Furthermore, a method for providing protection against infection with flaviviruses by induces of the secretory IgA and IgG antibodies is also provided. The nasal vaccine includes an inactivated antigen of a flavivirus and poly(I:C) or a ceramified powder of surf clam shells as an adjuvant. The vaccine effectively induces secretion of IgA antibodies in the nasal mucosa and serum IgG antibody responses. Also provided is a method for inducing flavivirus-specific IgA and IgG antibodies, including administering an inactivated antigen of a flavivirus and poly(I:C) or a ceramified powder of surf clam shells as an adjuvant to the mucosa of a respiratory tract.

Abstract: The present invention provides an adjuvant that possesses a greater adjuvant potential than that of a conventional adjuvant, and that is capable of producing a protective reaction across different strains. This problem has been solved by the finding that a double-stranded RNA (for example, Poly(I:C)) unexpectedly exhibits the above capability when used in combination with a subunit antigen. Accordingly, the present invention provides a vaccine for mucosal administration containing A) a double-stranded RNA and B) a subunit antigen or inactivated antigen of a pathogen.