Welts appeared on back of left arm diagnosed as hives/ arm welts; cellulitis in the arm; Swollen arm; Red rash was spreading down arm toward elbow/; injection site hot to touch; injection site looks bruised; Itaching on left arm; redness at the injection site; Arm Rash; Sore arm/left arm at injection site slightly sore; This spontaneous case was reported by a consumer and describes the occurrence of CELLULITIS (cellulitis in the arm), URTICARIA (Welts appeared on back of left arm diagnosed as hives/ arm welts) and RASH (Arm Rash) in a 71-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 044B21A and 037A21B) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Concurrent medical conditions included Marginal zone lymphoma since 01-Jun-2021 and Sulfonamide allergy. Concomitant products included ACETYLSALICYLIC ACID (BABY ASPIRIN) for Heart disorder, ATORVASTATIN for Hypercholesterolemia, LEVOTHYROXINE from 05-Jan-2021 to an unknown date for Thyroid disorder, CALCIUM ASCORBATE (VITAMIN C [CALCIUM ASCORBATE]) and COLECALCIFEROL (VITAMIN D 3) for an unknown indication.   On 17-Apr-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) .5 milliliter. On 15-May-2021 at 11:30 AM, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 16-May-2021,  after starting mRNA-1273 (Moderna COVID-19 Vaccine), the patient experienced VACCINATION SITE PAIN (Sore arm/left arm at injection site slightly sore). On 17-May-2021, the patient experienced RASH (Arm Rash) (seriousness criterion medically significant) and VACCINATION SITE PRURITUS (Itaching on left arm). 17-May-2021, the patient experienced VACCINATION SITE ERYTHEMA (redness at the injection site). On 19-May-2021, the patient experienced PERIPHERAL SWELLING (Swollen arm), RASH ERYTHEMATOUS (Red rash was spreading down arm toward elbow/), VACCINATION SITE WARMTH (injection site hot to touch) and VACCINATION SITE BRUISING (injection site looks bruised). On 20-May-2021, the patient experienced CELLULITIS (cellulitis in the arm) (seriousness criterion medically significant). On 23-May-2021 at 7:30 PM, the patient experienced URTICARIA (Welts appeared on back of left arm diagnosed as hives/ arm welts) (seriousness criterion medically significant). The patient was treated with DOXYCYCLINE for Cellulitis, at a dose of 50 milligram twice a day; DIPHENHYDRAMINE HYDROCHLORIDE (BENADRYL [DIPHENHYDRAMINE HYDROCHLORIDE]) ongoing since an unknown date at an unspecified dose and frequency; HYDROXYZINE on 23-May-2021 for Hives, at a dose of 25 milligram every six hours and HYDROCORTISONE (topical) on 23-May-2021 for Hives, at an unspecified dose and frequency. On 30-May-2021, CELLULITIS (cellulitis in the arm), URTICARIA (Welts appeared on back of left arm diagnosed as hives/ arm welts), RASH (Arm Rash), PERIPHERAL SWELLING (Swollen arm), RASH ERYTHEMATOUS (Red rash was spreading down arm toward elbow/), VACCINATION SITE WARMTH (injection site hot to touch), VACCINATION SITE BRUISING (injection site looks bruised), VACCINATION SITE PRURITUS (Itaching on left arm), VACCINATION SITE ERYTHEMA (redness at the injection site) and VACCINATION SITE PAIN (Sore arm/left arm at injection site slightly sore) had resolved.        For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter did not provide any causality assessments.   Company Comment: Based on the current available information and temporal association between the use of the product and the start date of the events, a causal relationship cannot be excluded.  The action taken with mRNA-1273 in response to event was not applicable   This case was linked to MOD-2021-148681 (Patient Link).   Most recent FOLLOW-UP information incorporated above includes: On 21-May-2021: Significant follow up: Serious event added (cellulitis). On 23-Jun-2021: Patient's demographics updated, Medical history updated- (allergy), Concomitant medications updated - (start date , dose , indication), Suspect vaccine updated- (dose 2 start time),  Event details updated- ((new event- hives),  seriousness criteria , outcome , stop date of other events), Treatment medications updated; Sender's Comments: Based on the current available information and temporal association between the use of the product and the start date of the events, a causal relationship cannot be excluded.