Could not lift her left arm; Pain in the wrist / She can't squeeze her hand or make a fist; Can't put pressure in the hand/Can't make a fist; Pain in the pinky and ring finger; breastfeeding; This case was received via an unknown source (no reference has been entered for a health authority or license partner) on 24-Nov-2021 and was forwarded to Moderna on 24-Nov-2021.    This spontaneous case was reported by a nurse and describes the occurrence of DISCOMFORT (Can't put pressure in the hand/Can't make a fist), PAIN IN EXTREMITY (Pain in the pinky and ring finger), MOBILITY DECREASED (Could not lift her left arm), ARTHRALGIA (Pain in the wrist / She can't squeeze her hand or make a fist) and MATERNAL EXPOSURE DURING BREAST FEEDING (breastfeeding) in a 34-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 053E21A) for COVID-19 vaccination.     Concomitant products included MINERALS NOS, VITAMINS NOS (PRENATAL VITAMINS [MINERALS NOS;VITAMINS NOS]) for an unknown indication.   On 31-Oct-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. On an unknown date, the patient received dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) at an unspecified dose. On 31-Oct-2021, the patient experienced MATERNAL EXPOSURE DURING BREAST FEEDING (breastfeeding). On 01-Nov-2021, the patient experienced MOBILITY DECREASED (Could not lift her left arm). In November 2021, the patient experienced DISCOMFORT (Can't put pressure in the hand/Can't make a fist), PAIN IN EXTREMITY (Pain in the pinky and ring finger) and ARTHRALGIA (Pain in the wrist / She can't squeeze her hand or make a fist). On 31-Oct-2021, MATERNAL EXPOSURE DURING BREAST FEEDING (breastfeeding) had resolved. On 03-Nov-2021, MOBILITY DECREASED (Could not lift her left arm) had resolved. At the time of the report, DISCOMFORT (Can't put pressure in the hand/Can't make a fist), PAIN IN EXTREMITY (Pain in the pinky and ring finger) and ARTHRALGIA (Pain in the wrist / She can't squeeze her hand or make a fist) outcome was unknown.        The action taken with mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown Route) and mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) was unknown.   For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter did not provide any causality assessments.   Treatment medication was not provided.  Next day after vaccine patient could not lift her left arm; this happened toward the evening. She could not lift the left arm unless she picked it up with the right arm. After 48 hours it went away, the pain started on 01-Nov-2021 and went away on 03-Nov-2021. On 11-Nov-2021/12-Nov-2021 she had pain in the wrist. She could not squeeze her hand or make a fist, also could not put pressure in the hand, could not push the stroller with the left hand. She could not turn the wheel of the car with her left hand because whenever she put pressure on it, it got hurt. She had pain in the pinky and ring finger. She also had pain where the pinky meets the wrist. She felt it when she touched it or put pressure on it. She was breastfeeding. She supposed to get the second dose on 28-Nov-2021. She stated, she did not know what to do.  The expiration date for the first dose was not provided. Patient was not taking other medication. Patient was taking prenatal vitamins. HCP was not aware of the side effects. Company comment: This spontaneous case concerns a 34 year old female , with no reported medical history, who experienced Non-serious , unexpected event of maternal exposure during breastfeeding which occurred on the same day of vaccination with the 1st dose of mRNA-1273 vaccine (  Moderna Covid 19 Vaccine ) . This was accompanied by other non-serious , unexpected events  mobility decreased, discomfort, pain in extremity and  expected event of arthralgia . The re-challenge for this case is not  applicable. The benefit -risk relationship of mRNA -1273 ( Moderna Covid 19 Vaccine) is not affected by this report; Sender's Comments: This spontaneous case concerns a 34 year old female , with no reported medical history, who experienced Non-serious , unexpected event of maternal exposure during breastfeeding which occurred on the same day of vaccination with the 1st dose of mRNA-1273 vaccine (  Moderna Covid 19 Vaccine ) . This was accompanied by other non-serious , unexpected events  mobility decreased, discomfort, pain in extremity and  expected event of arthralgia . The re-challenge for this case is not  applicable. The benefit -risk relationship of mRNA -1273 ( Moderna Covid 19 Vaccine) is not affected by this report.