Pfizer COVID-19 vaccines followed by a dose of the Moderna COVID-19 vaccines; Pfizer COVID-19 vaccines followed by a dose of the Moderna COVID-19 vaccines; she developed a cellulitis; Her arm really hurt, though her arm has always hurt after each and every covid vaccine; Developed a rash at the site and rash was spreading; This spontaneous case was reported by a consumer and describes the occurrence of CELLULITIS (she developed a cellulitis) in an elderly female patient who received mRNA-1273.815 (SPIKEVAX 2023-2024 PFS) (batch no. 3030335) for COVID-19 prophylaxis. The occurrence of additional non-serious events is detailed below.     Previously administered products included for Product used for unknown indication: flu shot (about 4 weeks before in the same arm. Left arm.) on 03-Sep-2023, Pfizer COVID-19 vaccines (Dose 5), Pfizer COVID-19 vaccines (Dose 3), Pfizer COVID-19 vaccines (Dose 4), Pfizer COVID-19 vaccines (Dose 1) and Pfizer COVID-19 vaccines (Dose 2). Past adverse reactions to the above products included No adverse event with Pfizer COVID-19 vaccines, Pfizer COVID-19 vaccines, Pfizer COVID-19 vaccines, Pfizer COVID-19 vaccines, Pfizer COVID-19 vaccines and flu shot.    On 20-Sep-2023, the patient received sixth dose of mRNA-1273.815 (SPIKEVAX 2023-2024 PFS) (unknown route) 1 dosage form. In 2023, the patient experienced CELLULITIS (she developed a cellulitis) (seriousness criterion medically significant), PAIN IN EXTREMITY (Her arm really hurt, though her arm has always hurt after each and every covid vaccine) and VACCINATION SITE RASH (Developed a rash at the site and rash was spreading). On 20-Sep-2023,  after starting mRNA-1273.815 (SPIKEVAX 2023-2024 PFS), the patient experienced COVID-19 IMMUNISATION (Pfizer COVID-19 vaccines followed by a dose of the Moderna COVID-19 vaccines). On an unknown date, the patient experienced INTERCHANGE OF VACCINE PRODUCTS (Pfizer COVID-19 vaccines followed by a dose of the Moderna COVID-19 vaccines). The patient was treated with CEFALEXIN MONOHYDRATE (CEPHALEXIN [CEFALEXIN MONOHYDRATE]) at a dose of 500mg, 4x daily for 10 days. At the time of the report, CELLULITIS (she developed a cellulitis), PAIN IN EXTREMITY (Her arm really hurt, though her arm has always hurt after each and every covid vaccine) and VACCINATION SITE RASH (Developed a rash at the site and rash was spreading) had not resolved and COVID-19 IMMUNISATION (Pfizer COVID-19 vaccines followed by a dose of the Moderna COVID-19 vaccines) and INTERCHANGE OF VACCINE PRODUCTS (Pfizer COVID-19 vaccines followed by a dose of the Moderna COVID-19 vaccines) outcome was unknown.        For mRNA-1273.815 (SPIKEVAX 2023-2024 PFS) (Unknown), the reporter did not provide any causality assessments.   No concomitant medication was reported.  A few days after receiving that vaccine she developed a cellulitis. Her arm really hurt, though her arm has always hurt after each and every covid vaccine. This pain did not go away for a couple days. Developed a rash at the site and rash was spreading. Went to an urgent care where a PA said she should take 10 days of antibiotics.  Cephalexin 500mg, 4x daily for 10 days. This was for a diagnosed cellulitis.  Company Comment: This is a spontaneous case concerning an elderly female patient with no reported medical history, who experienced the serious (due to medically significant) unexpected event of Cellulitis among other non-serious events. The event Cellulitis occurred on an unknown date after the first dose of SPIKEVAX 2023-2024 PFS received as the fifth dose of COVID-19 vaccination schedule. The patient had received a flu shot (about 4 weeks before in the same arm. Left arm.) on 03-Sep-2023, and previous 5 doses of Pfizer COVID-19 vaccine; so COVID-19 Immunisation and Interchange of vaccine products were also noted in the case. A few days after receiving that vaccine the patient developed a cellulitis; her arm really hurt, and though her arm had always hurt after each and every COVID vaccine, the pain had not gone away for a couple days. The patient also developed a rash at the site and rash was spreading, so she went to an urgent care where she was diagnosed with Cellulitis and was prescribed with antibiotics for 10 days.The outcome of the event was reported as not recovered. The benefit-risk relationship of SPIKEVAX 2023-2024 PFS vaccine is not affected by this report.