Blood in stool; Ulcerative colitis; Stomach bubbling/rallying in belly; Pure black stool; Arm hurts/very sore arm; Belly aches; Diarrhoea; Inappropriate schedule of product administration; This spontaneous case was reported by a consumer and describes the occurrence of HAEMATOCHEZIA (Blood in stool) and COLITIS ULCERATIVE (Ulcerative colitis) in a 65-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Previously administered products included for COVID-19 vaccination: Pfizer on 16-Mar-2021 and Pfizer on 10-Apr-2021. Past adverse reactions to the above products included Pain in arm with Pfizer and Pfizer.    On 26-Oct-2021, the patient received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 26-Oct-2021, the patient experienced INAPPROPRIATE SCHEDULE OF PRODUCT ADMINISTRATION (Inappropriate schedule of product administration). On 27-Oct-2021, the patient experienced HAEMATOCHEZIA (Blood in stool) (seriousness criterion medically significant), COLITIS ULCERATIVE (Ulcerative colitis) (seriousness criterion medically significant), ABDOMINAL PAIN (Belly aches) and DIARRHOEA (Diarrhoea). 27-Oct-2021, the patient experienced ABDOMINAL DISCOMFORT (Stomach bubbling/rallying in belly), FAECES DISCOLOURED (Pure black stool) and PAIN IN EXTREMITY (Arm hurts/very sore arm). The patient was treated with BISMUTH SUBSALICYLATE (PEPTO-BISMOL) on 27-Oct-2021 for Adverse event, at an unspecified dose and frequency. On 26-Oct-2021, INAPPROPRIATE SCHEDULE OF PRODUCT ADMINISTRATION (Inappropriate schedule of product administration) had resolved. At the time of the report, HAEMATOCHEZIA (Blood in stool), ABDOMINAL DISCOMFORT (Stomach bubbling/rallying in belly), FAECES DISCOLOURED (Pure black stool) and PAIN IN EXTREMITY (Arm hurts/very sore arm) had not resolved and COLITIS ULCERATIVE (Ulcerative colitis), ABDOMINAL PAIN (Belly aches) and DIARRHOEA (Diarrhoea) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 27-Oct-2021, Haemoglobin: 12 (normal) Normal.         Concomitant product use was not provided. Patient took Pfizer vaccine as primary vaccination. It is stated that patient experienced arm hurts which was more than it did with Pfizer. Patient took Pepto-Bismol in the morning on 27 Oct 2021. It is stated that the black tool could showed blood when it was separated on a paper. Patient also had belly ache, but it was not too bad.  Company Comment : This case of inappropriate schedule of vaccine administered concerning 65-year-old female patient, with past medical history of pain in arm with Pfizer and Pfizer, who experienced unexpected events of hematochaezia and ulcerative colitis.  The events occurred approximately 1 day after the third dose of mRNA-1273 (Moderna COVID-19 Vaccine). The rechallenge is not applicable since the event was reported exclusively after the third dose. The benefit-risk relation of Moderna COVID-19 Vaccine is not affected by this report.   Most recent FOLLOW-UP information incorporated above includes: On 28-Oct-2021: Follow-up received added lab data and events.; Sender's Comments: This case of inappropriate schedule of vaccine administered concerning 65-year-old female patient, with past medical history of pain in arm with Pfizer and Pfizer, who experienced unexpected events of hematochaezia and ulcerative colitis.  The events occurred approximately 1 day after the third dose of mRNA-1273 (Moderna COVID-19 Vaccine). The rechallenge is not applicable since the event was reported exclusively after the third dose. The benefit-risk relation of Moderna COVID-19 Vaccine is not affected by this report.