swelling of the ulnar nerve in the axilla; numbness in his fingers; left arm (where the injection site was) swollen; left axilla painful; booster dose (3rd dose) given at 0.5ml to a non immunocompromised person; This spontaneous case was reported by a physician and describes the occurrence of NEURITIS (swelling of the ulnar nerve in the axilla), HYPOAESTHESIA (numbness in his fingers), VACCINATION SITE SWELLING (left arm (where the injection site was) swollen), AXILLARY PAIN (left axilla painful) and ACCIDENTAL OVERDOSE (booster dose (3rd dose) given at 0.5ml to a non immunocompromised person) in an 88-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination.     Concurrent medical conditions included Overweight.    On 18-Sep-2021, the patient received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) .5 milliliter. On 18-Sep-2021, the patient experienced ACCIDENTAL OVERDOSE (booster dose (3rd dose) given at 0.5ml to a non immunocompromised person). On an unknown date, the patient experienced NEURITIS (swelling of the ulnar nerve in the axilla), HYPOAESTHESIA (numbness in his fingers), VACCINATION SITE SWELLING (left arm (where the injection site was) swollen) and AXILLARY PAIN (left axilla painful). The patient was treated with NAPROXEN for Adverse event, at an unspecified dose and frequency and DOXYCYCLINE for Adverse event, at an unspecified dose and frequency. At the time of the report, NEURITIS (swelling of the ulnar nerve in the axilla), HYPOAESTHESIA (numbness in his fingers), VACCINATION SITE SWELLING (left arm (where the injection site was) swollen) and AXILLARY PAIN (left axilla painful) had resolved and ACCIDENTAL OVERDOSE (booster dose (3rd dose) given at 0.5ml to a non immunocompromised person) outcome was unknown.        For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   No concomitant medications were reported. Patient reported that he initially thought he had tenosynovitis. It was also reported that he went to the ER 3x. Treatment medications also included steroids. Patient reported that nothing of the treatment worked but events went away by itself.  Company comment:This spontaneous case concerns an 88 year old male, with unknown medical history, who experienced the non-serious expected events of vaccination site swelling, axillary pain,and hypoaestesia and the non-serious unexpected event of neuritis, after receiving a 0.5 milliliter booster dose of mRNA-1273. Accidental overdose was also captured, as patient states he had no indication to receive a complete third dose. Patient received steroids, naproxen and doxyclicne as treatment. Lyme disease was suspected, but no information regarding confirmation was provided. The benefit-risk relationship of mRNA-1273 is not affected by this report.   This case was linked to MOD-2022-515838.; Sender's Comments: This spontaneous case concerns an 88 year old male, with unknown medical history, who experienced the non-serious expected events of vaccination site swelling, axillary pain,and hypoaestesia and the non-serious unexpected event of neuritis, after receiving a 0.5 milliliter booster dose of mRNA-1273. Accidental overdose was also captured, as patient states he had no indication to receive a complete third dose. Patient received steroids, naproxen and doxyclicne as treatment. Lyme disease was suspected, but no information regarding confirmation was provided. The benefit-risk relationship of mRNA-1273 is not affected by this report.