A single vaccination of animals with diphtheria-tetanus vaccine caused changes in non-specific resistance of the organism to influenza of phasic character: a reduction of resistance to influenza was observed at the early periods after the vaccination, with its subsequent restoration to the initial level and increase at the remote periods after the immunization. Immunization of children with diphtheria-tetanus vaccine also led to a short-term reduction non-specific resistance to influenza and acute respiratory diseases during the second decade after the vaccination, and its subsequent increase at periods from the 40th to the 60th day.