This spontaneous case was reported by a nurse and describes the occurrence of CELLULITIS (Diagnosed with Cellulitis after first shot/Lymph Edema on left Deltoid down to left elbow 1 week after first shot/Lymph Edema on the left side of neck 1 week after first shot) in a 71-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 031L20A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below. The patient's past medical history included Immune disorder (NOS) (very immune reactive.) since 1988. On 17-Feb-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 17-Feb-2021, the patient experienced VACCINATION SITE RASH (Large Macular Rash Left arm Injection Site after first shot). On 26-Feb-2021, the patient experienced CELLULITIS (Diagnosed with Cellulitis after first shot/Lymph Edema on left Deltoid down to left elbow 1 week after first shot/Lymph Edema on the left side of neck 1 week after first shot) (seriousness criterion medically significant). The patient was treated with CEFALEXIN MONOHYDRATE (KEFLEX [CEFALEXIN MONOHYDRATE]) for Adverse event, at an unspecified dose and frequency. On 11-Mar-2021, CELLULITIS (Diagnosed with Cellulitis after first shot/Lymph Edema on left Deltoid down to left elbow 1 week after first shot/Lymph Edema on the left side of neck 1 week after first shot) and VACCINATION SITE RASH (Large Macular Rash Left arm Injection Site after first shot) had resolved. mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown) dosing remained unchanged. For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments. No concomitant medications were reported. She did not take Steroids or Ibuprofen. Company comment: This spontaneous case concerns a 71-years-old female patient, with past medical history of Positive ANA and Immune disorder, who experienced unexpected serious (seriousness criterion medically significant) event of cellulitis, which occurred 9 days after first dose of mRNA-1273 vaccine. The patient experienced vaccination site macular rash on the left arm on the same day after administration of the first dose. The patient experienced Lymph Edema on left Deltoid down to left elbow 1 week after first shot and was diagnosed with Cellulitis. The patient was treated with Cefalexin Monohydrate. Past medical history of Positive ANA and Immune disorder remains as confounding. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report. This case was linked to MOD-2022-551599, MOD-2022-551605 (Patient Link). Sender's Comments: This spontaneous case concerns a 71-years-old female patient, with past medical history of Positive ANA and Immune disorder, who experienced unexpected serious (seriousness criterion medically significant) event of cellulitis, which occurred 9 days after first dose of mRNA-1273 vaccine. The patient experienced vaccination site macular rash on the left arm on the same day after administration of the first dose. The patient experienced Lymph Edema on left Deltoid down to left elbow 1 week after first shot and was diagnosed with Cellulitis. The patient was treated with Cefalexin Monohydrate. Past medical history of Positive ANA and Immune disorder remains as confounding. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.