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.