An analysis of clinico-immunological data has demonstrated a considerable decline in non-specific and specific defences against such major factors of hospital infection in esophageal cancer patients as staphylococcal, blue pus and Proteus bacilli. Immunization with a complex vaccine including concentrated staphylococcal anatoxin, blue pus and Proteus vaccines was shown to stimulate the said factors of anti-infectious immunity and to be followed by a 4.7-fold decrease in the incidence of postoperative pyo-inflammatory complications. The said vaccine may be recommended for prevention of infectious complications in cancer patients since its administration is followed by a low-level reaction matched by a marked increase in immunologic vigor.