feels tight, like he pulled a muscle; feels tight, like he pulled a muscle; next morning after his first dose, his whole left side was numb; reports muscle pain from the middle of the chest to where the vaccine was injected; muscle pain; pain down his left arm; pain in sternum to left arm, whole shoulder area; hard time using left arm/cannot reach above his head; pain in the middle of chest, sternum to the left arm; developed A fib; sometimes he is basically immobilized; it felt like was having a heart attack; muscle pain, muscle cramps and it felt like he was having heart attack; pain down left arm and up neck in side; This spontaneous case was reported by a patient and describes the occurrence of ATRIAL FIBRILLATION (developed A fib) in a 70-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 032M20A, 0027A21A and 84J21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Concurrent medical conditions included Mental disorder (Suffer from mental health problems (unrelated to vaccination).).   On 02-Mar-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 31-Mar-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 30-Jan-2022, received dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 03-Mar-2021, the patient experienced MUSCLE STRAIN (feels tight, like he pulled a muscle), MUSCLE TIGHTNESS (feels tight, like he pulled a muscle) and HYPOAESTHESIA (next morning after his first dose, his whole left side was numb). In March 2021, the patient experienced ATRIAL FIBRILLATION (developed A fib) (seriousness criterion medically significant), IMMOBILE (sometimes he is basically immobilized), FEELING ABNORMAL (it felt like was having a heart attack), MUSCLE SPASMS (muscle pain, muscle cramps and it felt like he was having heart attack), NECK PAIN (pain down left arm and up neck in side), LIMB DISCOMFORT (hard time using left arm/cannot reach above his head), CHEST PAIN (pain in the middle of chest, sternum to the left arm), ARTHRALGIA (pain in sternum to left arm, whole shoulder area), VACCINATION SITE PAIN (reports muscle pain from the middle of the chest to where the vaccine was injected), MYALGIA (muscle pain) and PAIN IN EXTREMITY (pain down his left arm). The patient was treated with IBUPROFEN at an unspecified dose and frequency and PARACETAMOL (TYLENOL) at an unspecified dose and frequency. At the time of the report, ATRIAL FIBRILLATION (developed A fib), IMMOBILE (sometimes he is basically immobilized), FEELING ABNORMAL (it felt like was having a heart attack), MUSCLE SPASMS (muscle pain, muscle cramps and it felt like he was having heart attack), MUSCLE STRAIN (feels tight, like he pulled a muscle), LIMB DISCOMFORT (hard time using left arm/cannot reach above his head), MUSCLE TIGHTNESS (feels tight, like he pulled a muscle), ARTHRALGIA (pain in sternum to left arm, whole shoulder area) and HYPOAESTHESIA (next morning after his first dose, his whole left side was numb) outcome was unknown and NECK PAIN (pain down left arm and up neck in side), CHEST PAIN (pain in the middle of chest, sternum to the left arm), VACCINATION SITE PAIN (reports muscle pain from the middle of the chest to where the vaccine was injected), MYALGIA (muscle pain) and PAIN IN EXTREMITY (pain down his left arm) was resolving.        mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown) dosing remained unchanged.       No concomitant medications were reported.  Patient reported that after receiving his first dose of the Moderna COVID-19 vaccine 1 year and 4 months ago on 02-Mar-2021, he started to experience muscle pain, muscle cramps, it felt like he was having a heart attack. He reports muscle pain from the middle of the chest to where the vaccine was injected. He reports pain down his left arm and up the neck in the side. He reports that he spoke to his doctor, who called him crazy, and he reports he does suffer from mental health problems (unrelated to vaccination). Patient reports the next morning after his first dose, his whole left side was numb. It feels very tight, like he pulled a muscle. He has a hard time using his left arm, he reports cramps, cannot reach above his head. He reports sometimes he is basically immobilized, the pain subsides, but it does not go away. Patient reports pain in the middle of chest, sternum to the left arm, whole shoulder area.   Patient laboratory data was reported as couple of EKGs and ultrasound with no results reported and 24-hour heart monitor since the shot.  Patient treatment information included pickle juice and tried to exercise.  Company Comment:Company comment: This is a spontaneous case concerning a 70-year-old male patient with medical history of mental disorder, who experienced the serious (medically significant) unexpected AESI Atrial fibrillation, on an unknown date after the first dose of mRNA-1273.  Patient reports pain in the middle of the chest, sternum to left arm, and experienced feeling "like he was having a heart attack". He reports diagnostic test had been performed (EKG, ultrasound, 24 hours heart monitor) without reporting results. Other non-serious events were also described.  Further information has been requested. The benefit-risk relationship of mRNA-1273 is not affected by this report.; Sender's Comments: Company comment: This is a spontaneous case concerning a 70-year-old male patient with medical history of mental disorder, who experienced the serious (medically significant) unexpected AESI Atrial fibrillation, on an unknown date after the first dose of mRNA-1273.  Patient reports pain in the middle of the chest, sternum to left arm, and experienced feeling "like he was having a heart attack". He reports diagnostic test had been performed (EKG, ultrasound, 24 hours heart monitor) without reporting results. Other non-serious events were also described.  Further information has been requested. The benefit-risk relationship of mRNA-1273 is not affected by this report.