Infection of cellulitis; fever; chills; This spontaneous case was reported by a consumer and describes the occurrence of CELLULITIS (Infection of cellulitis) in a 52-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.    Co-suspect product included non-company product PNEUMOCOCCAL VACCINE for Pneumonia.    No Medical History information was reported.   On 22-Nov-2021, the patient received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 22-Nov-2021, the patient received dose of PNEUMOCOCCAL VACCINE (Intramuscular) 1 dosage form. On an unknown date, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On an unknown date, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. In November 2021, the patient experienced PYREXIA (fever) and CHILLS (chills). On 26-Nov-2021,  after starting mRNA-1273 (Moderna COVID-19 Vaccine), the patient experienced CELLULITIS (Infection of cellulitis) (seriousness criterion medically significant). The patient was treated with DIPHENHYDRAMINE HYDROCHLORIDE (BENADRYL [DIPHENHYDRAMINE HYDROCHLORIDE]) on 24-Nov-2021 for Vaccination site erythema, at an unspecified dose and frequency and SULFAMETHOXAZOLE for Cellulitis, at an unspecified dose and frequency. On 03-Dec-2021, CELLULITIS (Infection of cellulitis) was resolving and PYREXIA (fever) and CHILLS (chills) had resolved.        For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   Patient stated that she experienced symptoms due to improper vaccine administration by the pharmacy. Pharmacy administered booster dose and pneumonia vaccine in same left arm on 22nd November 2021. On 26th November 2021 patient went to the emergency room as the rash became 6 by 5 inches and she was diagnosed with infection of cellulitis. States she also had fever and chills. Says she had cellulitis symptoms for about 6 days and by 3Dec2021 most of symptoms were gone except a small patch at injection site.  Treatment: Benadryl and ER prescribed sulfamethoxazole DS  Company comment: This spontaneous case concerns a 52-year-old female patient with no relevant medical history and concurrent administration of co-suspect pneumococcal vaccine who experienced serious unexpected event of cellulitis. The event occurred approximately 4 days after the booster dose of the mRNA-1273 . The patient had light pink area on the left arm after vaccination and took Benadryl however, the rash spread so the patient went to ER and was diagnosed with cellulitis. The patient was treated with sulfamethoxazole DS. Most of the symptoms resolved except patch at the injection site. The rechallenge was not applicable since the event occurred after the booster dose so, no rechallenge was done and recurrence was not applicable.  The benefit-risk relationship of mRNA-1273 is not affected by this report.; Sender's Comments: This spontaneous case concerns a 52-year-old female patient with no relevant medical history and concurrent administration of co-suspect pneumococcal vaccine who experienced serious unexpected event of cellulitis. The event occurred approximately 4 days after the booster dose of the mRNA-1273 . The patient had light pink area on the left arm after vaccination and took Benadryl however, the rash spread so the patient went to ER and was diagnosed with cellulitis. The patient was treated with sulfamethoxazole DS. Most of the symptoms resolved except patch at the injection site. The rechallenge was not applicable since the event occurred after the booster dose so, no rechallenge was done and recurrence was not applicable.  The benefit-risk relationship of mRNA-1273 is not affected by this report.