The present invention relates to a RNA encoding an antibody or a fragment or variant thereof and a composition, in particular a passive vaccine, comprising such an RNA. The present invention further relates to the use of such an RNA or of such a composition for treatment of tumours and cancer diseases, cardiovascular diseases, infectious diseases, autoimmune diseases, virus diseases and monogenetic diseases, e.g. also in gene therapy. The present invention also relates to a combination of at least two modified RNA's, in particular wherein one RNA encodes a heavy chain variable region of an antibody and another RNA encodes the corresponding light chain variable region of said antibody.