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Background: The Brazilian government has established disease eradication and control programs to protect livestock from pathogens that affect animal health and compromise animal protein production and food safety and quality. Vaccination campaigns against foot-and-mouth disease and other infectious diseases in cattle except brucellosis can be carried out bynon-veterinarian employees. However, vaccination errors can result in the formation of granulomas at injection sites that can affect animal welfare and production. The present study aimed to report two cases of granulomas at injection sites due to the inadvertent administration of vaccines containing saponins and mineral oil as adjuvants.Cases: Case 1. The history was that a 2-year-old Devon steer was down for 7 days and was vaccinated 20 days ago with a vaccine containing saponins and mineral oil as adjuvants. Case 2. A 7-month-old Holstein heifer was examinated due to a 40-day history of ataxia, forelimb paresis progressing to tetraparesis, and vaccination with a vaccine containing saponins and mineral oil as adjuvants 60 days ago. These two animals were admitted in the Veterinary Hospital from the University of Passo Fundo (UPF) with a clinical history of incoordination and permanent decubitus after vaccination. The disease had a similar clinical course in both animals. Clinical signs included the presence of a palpable cervical mass at the site of vaccination, forelimb paresis that progressed to tetraparesis, and decubitus scars. Treatment included intravenousadministration of anti-inflammatory steroids, antibiotic therapy, daily cleansing of the pressure sores, all four limbs were massaged, animals underwent several physiotherapy sessions, slings were used to mantain recumbent patients in a standing position and supportive therapy consisted of fluid therapy and oral supplementation. Animals remained hospitalizedfor approximately 40 days. Pacients experienced temporary improvement during treatment, and would walk with an uncoordinated gait. The clinical picture worsened after treatment was discontinued, necessitating euthanasia. At necropsy, gross lesions were similar in both animals. In case 1, the trapezius was firm and pale and had multiple granulomas whichextended into the cervical vertebral column at C3-C4 and invaded the spinal canal compressing the spinal cord. In case 2, there was extensive damage to the trapezius by granulomatous inflammation; numerous nodular granulomas exuded milky contents. These lesions extended deep into the muscle fibers and infiltrated the vertebral column at C5-C6, with involvement of the medullary canal and spinal cord compression. Microscopically there was severe, diffuse pyogranulomatous myositis. Each pyogranuloma had a central clear space. Nodal architecture was effaced by these inflammatory nodules.Discussion: Some drugs and vaccines contain irritating adjuvants and induce granuloma formation at the inoculation site. In both cattle, vaccines were injected intramuscularly in the cranial third of the neck in close proximity to the cervical vertebrae and surrounding tissues. These vaccines possibly induced an exuberant inflammatory reaction at the inoculationsite. An exacerbated inflammatory response following the administration of adjuvanted vaccines by improperly trained personnel caused substantial tissue damage at the injection site. Severe, locally extensive lesions were found at necropsy affecting adjacent structures including skeletal muscles and spinal cord. The clinical signs of ataxia and forelimb paresis thatprogressed to tetraparesis were due to the marked pyogranulomatous inflammation in C3-C4 in case 1 and in C5-C6 in case 2. The present study reinforces the importance of good farming practices and properly trained personnel working at farms.Keywords: bovine, vaccine, infection site, granuloma, iatrogenic.