This spontaneous case was reported by a consumer and describes the occurrence of URINARY RETENTION (Urinary retention/Cannot pee after receiving the second booster dose) in a 75-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 002M21A and 026D21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below. Concurrent medical conditions included Penicillin allergy, Blood pressure high and Cholesterol. On 22-Oct-2021, the patient received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 06-Apr-2022, received fourth dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 06-Apr-2022, the patient experienced URINARY RETENTION (Urinary retention/Cannot pee after receiving the second booster dose) (seriousness criterion medically significant), URINARY TRACT INFECTION (Symptoms mimicked a lower urinary tract infection, Slight burnt while peeing, Lower back pain) and WEIGHT INCREASED (Gained 3 pounds due to the urinary retention). At the time of the report, URINARY RETENTION (Urinary retention/Cannot pee after receiving the second booster dose) had not resolved and URINARY TRACT INFECTION (Symptoms mimicked a lower urinary tract infection, Slight burnt while peeing, Lower back pain) and WEIGHT INCREASED (Gained 3 pounds due to the urinary retention) outcome was unknown. For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments. On 22-Oct-2021 patient received 1st Booster Dose. On 06-Apr-2022 patient received 2nd Booster Dose. Concomitant product included high blood pressure medication and Cholesterol medication. The patient received the second booster dose on 06Apr2022 and within 8 hours the patient could not pee. She had urinary retention and was not able to urinate. The patient states that could urinate a little, but it burnt slightly when did and she also experienced lower back pain. She states that all symptoms mimicked a lower urinary tract infection. She states that she gained 3 pounds due to the urinary retention. The patient cannot still fully urinate and had slight burning. Caller states that she did not take any medication for the symptoms. Caller states that she takes regular medication for high blood pressure and Cholesterol. The patient never had COVID test or diagnosis. No treatment medication were reported. Company comment: This spontaneous case concerns a 75 year old female patient with relevant medical history, who experienced the unexpected serious (important medical event) event of Urinary retention, about 1 year and 2 months after receiving the fourth dose (2nd booster) of mRNA-1273 vaccine. Patient also had dysuria, urinary tract infection and back pain with the event. No further information on clinical course and management of the event was available in the report. Elderly age of the patient could be a risk factor for the event. The benefit-risk relationship of mRNA-1273 is not affected by this report. This case was linked to MOD-2022-537574 (Patient Link). Sender's Comments: This spontaneous case concerns a 75 year old female patient with relevant medical history, who experienced the unexpected serious (important medical event) event of Urinary retention, about 1 year and 2 months after receiving the fourth dose (2nd booster) of mRNA-1273 vaccine. Patient also had dysuria, urinary tract infection and back pain with the event. No further information on clinical course and management of the event was available in the report. Elderly age of the patient could be a risk factor for the event. The benefit-risk relationship of mRNA-1273 is not affected by this report.