The invention concerns monoclonal antibodies against the epitope YPYDVPDYA (SEQ ID NO: 1) which is derived from the haemagglutinin of the human influenza virus and are suitable for the detection and isolation of native haemagglutinin of the human influenza virus, of modified haemagglutinin or of haemagglutinin fusion proteins and have an affinity of >10.sup.8 M.sup.-1, in particular of 10.sup.9 to 10.sup.10 M.sup.-1.