Nasal preparation and processes for their production

The present invention relates to nasal preparations which contain, as active ingredient, one or more nitrogen-containing polysaccharides obtained from fungi, in particular the polysaccharide krestin, and which exert a prophylactic action lasting several days against infections caused by viruses of the respiratory tract, especially influenza A and B viruses, as well as vaccine nasal preparations which contain the above mentioned active ingredient together with viruses of the respiratory tract of at least one strain and which impart a long-term protective action on single administration. The invention is also concerned with the production and use of these nasal preparations.