Diagnosed with Aneurysm of Internal Carotid Artery 4mm 5 months after first booster; Diagnosed with a Pituitary  Tumor (Benign)  3 months after first booster; Lost hearing in the right ear after first booster; This spontaneous case was reported by a nurse and describes the occurrence of DEAFNESS UNILATERAL (Lost hearing in the right ear after first booster) and CAROTID ARTERY ANEURYSM (Diagnosed with Aneurysm of Internal Carotid Artery 4mm 5 months after first booster) in a 62-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 034F21A, 045B21A and 019B21A) for COVID-19 prophylaxis. The occurrence of additional non-serious events is detailed below.     No Medical History information was reported.   On 25-Mar-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 22-Apr-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 19-Dec-2021, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. In January 2022, the patient experienced DEAFNESS UNILATERAL (Lost hearing in the right ear after first booster) (seriousness criterion medically significant). On 25-Mar-2022,  after starting mRNA-1273 (Moderna COVID-19 Vaccine), the patient experienced PITUITARY TUMOUR BENIGN (Diagnosed with a Pituitary  Tumor (Benign)  3 months after first booster). In May 2022, the patient experienced CAROTID ARTERY ANEURYSM (Diagnosed with Aneurysm of Internal Carotid Artery 4mm 5 months after first booster) (seriousness criterion medically significant). The patient was treated with Surgery (Stent placement) for Carotid artery aneurysm. At the time of the report, DEAFNESS UNILATERAL (Lost hearing in the right ear after first booster), CAROTID ARTERY ANEURYSM (Diagnosed with Aneurysm of Internal Carotid Artery 4mm 5 months after first booster) and PITUITARY TUMOUR BENIGN (Diagnosed with a Pituitary  Tumor (Benign)  3 months after first booster) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 25-Mar-2022, Magnetic resonance imaging head: Did an MRI of the head for the ear problem and, found something else. The patient was diagnosed with a Pituitary Tumor (Benign). Surgery will be scheduled for Oct-2022.. In May 2022, Magnetic resonance imaging head: The second MRI revealed Aneurysm of Internal Carotid Artery 4mm. MD placed in a stent..     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   Concomitant medications was not provided by the reporter.  Dosage text was reported as first booster dose on 19-Dec-2021.  Treatment included MD placed in a stent for Aneurism of Internal Carotid Artery 4mm.  Company Comment: This is a spontaneous case concerning a 62-year-old male patient with no reported medical history, previously vaccinated with the primary series of COVID-19 vaccine mRNA-1273 (28 days interval between the 2 doses), who experienced the unexpected serious (medically significant) events of Deafness unilateral (Lost hearing in the right ear after first booster) and Carotid artery aneurysm (Internal carotid artery), and the non-serious event of Pituitary tumour benign. Event Deafness unilateral occurred unknown number of days (beginning of JAN2022) after the first booster dose of mRNA-1273 vaccine (19DEC2021), administered 7 months 7 days after the 2nd dose of mRNA-1273 Vaccine, event Pituitary tumour occurred about 3 months after vaccination, while event Carotid artery aneurysm occurred unknown number of days after vaccination. As reported, about 3 months after the first booster dose, cranial MRI was done to evaluate the hearing loss of the right ear which occurred approximately 3 months prior. He was diagnosed with a Pituitary Tumor (Benign) and scheduled for future surgery. Another cranial MRI was done at a different clinic on an unspecified date which showed an Aneurysm of Internal Carotid Artery 4mm for which a stent was placed. There is no available information regarding clinical course and treatment medication. The patient's age, which is a risk factor for all the events, remains a confounder. The benefit-risk relationship of mRNA-1273 Vaccine is not affected by this report.; Sender's Comments: This is a spontaneous case concerning a 62-year-old male patient with no reported medical history, previously vaccinated with the primary series of COVID-19 vaccine mRNA-1273 (28 days interval between the 2 doses), who experienced the unexpected serious (medically significant) events of Deafness unilateral (Lost hearing in the right ear after first booster) and Carotid artery aneurysm (Internal carotid artery), and the non-serious event of Pituitary tumour benign. Event Deafness unilateral occurred unknown number of days (beginning of JAN2022) after the first booster dose of mRNA-1273 vaccine (19DEC2021), administered 7 months 7 days after the 2nd dose of mRNA-1273 Vaccine, event Pituitary tumour occurred about 3 months after vaccination, while event Carotid artery aneurysm occurred unknown number of days after vaccination. As reported, about 3 months after the first booster dose, cranial MRI was done to evaluate the hearing loss of the right ear which occurred approximately 3 months prior. He was diagnosed with a Pituitary Tumor (Benign) and scheduled for future surgery. Another cranial MRI was done at a different clinic on an unspecified date which showed an Aneurysm of Internal Carotid Artery 4mm for which a stent was placed. There is no available information regarding clinical course and treatment medication. The patient's age, which is a risk factor for all the events, remains a confounder. The benefit-risk relationship of mRNA-1273 Vaccine is not affected by this report.