suspected cellulitis at left arm injection site; been quite unwell since getting my 3rd Moderna covid shot; localized reactions with alot of redness that went down her arm.; bed bound for a month.; She felt so sick; severe fatigue; had left arm inflammation and redness; had left arm redness; feeling of tired; mistakenly gave it to me subcutaneously/3rd dose was administered incorrect route by subcutaneous injection; This spontaneous case was reported by a nurse and describes the occurrence of CELLULITIS (suspected cellulitis at left arm injection site) in a 57-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 002F21A, 028B21A and 003A21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Concomitant products included AZATHIOPRINE SODIUM (IMURAN [AZATHIOPRINE SODIUM]) for lupus.   On 11-Mar-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 08-Apr-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. On 23-Aug-2021, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Subcutaneous) dosage was changed to 1 dosage form. On an unknown date, the patient experienced CELLULITIS (suspected cellulitis at left arm injection site) (seriousness criterion medically significant), MALAISE (been quite unwell since getting my 3rd Moderna covid shot), ERYTHEMA (localized reactions with alot of redness that went down her arm.), BEDRIDDEN (bed bound for a month.), ILLNESS (She felt so sick), FATIGUE (severe fatigue), VACCINATION SITE INFLAMMATION (had left arm inflammation and redness), VACCINATION SITE ERYTHEMA (had left arm redness), FATIGUE (feeling of tired) and INCORRECT ROUTE OF PRODUCT ADMINISTRATION (mistakenly gave it to me subcutaneously/3rd dose was administered incorrect route by subcutaneous injection). The patient was treated with PARACETAMOL (TYLENOL) at an unspecified dose and frequency and IBUPROFEN at an unspecified dose and frequency. On 30-Sep-2021, FATIGUE (feeling of tired) had resolved. At the time of the report, CELLULITIS (suspected cellulitis at left arm injection site), MALAISE (been quite unwell since getting my 3rd Moderna covid shot), ERYTHEMA (localized reactions with alot of redness that went down her arm.), BEDRIDDEN (bed bound for a month.), ILLNESS (She felt so sick), FATIGUE (severe fatigue), VACCINATION SITE INFLAMMATION (had left arm inflammation and redness) and VACCINATION SITE ERYTHEMA (had left arm redness) outcome was unknown and INCORRECT ROUTE OF PRODUCT ADMINISTRATION (mistakenly gave it to me subcutaneously/3rd dose was administered incorrect route by subcutaneous injection) had resolved.        For mRNA-1273 (Moderna COVID-19 Vaccine) (Subcutaneous), the reporter did not provide any causality assessments.   Company comment: This is a case of incorrect route of product administration and concerns a 57-year-old, female patient with medical history of lupus and concomitant use of imuran, who experienced the unexpected serious event of cellulitis. The event occurred on an unknown number of days after the third dose of mRNA 1273. The rechallenge is not applicable, since the vaccination schedule has been completed. The medical history of lupus and concomitant use of imuran, remain a confounder. The benefit-risk relationship of the vaccine is not affected by this report.   This case was linked to MOD-2021-341218, MOD-2021-341229 (Patient Link).   Most recent FOLLOW-UP information incorporated above includes: On 04-Oct-2021: Significant Follow-up appended.; Sender's Comments: This is a case of incorrect route of product administration and concerns a 57-year-old, female patient with medical history of lupus and concomitant use of imuran, who experienced the unexpected serious event of cellulitis. The event occurred on an unknown number of days after the third dose of mRNA 1273. The rechallenge is not applicable, since the vaccination schedule has been completed. The medical history of lupus and concomitant use of imuran, remain a confounder. The benefit-risk relationship of the vaccine is not affected by this report.