The present invention provides methods and adjuvants for enhancing an immune response to RSV in a host, wherein the methods and adjuvants comprise a source of a CD40 binding protein. Preferably, the CD40 binding protein is CD40L and the source is a vector comprising a promoter operatively linked to a CD40L coding region. The enhanced immune response produced by the adjuvants and methods of the current invention includes both increased expression of Th1 cytokines and increased production of antibody.