exacerbated arthritis in knees/Since about 4 to 6 weeks after the booster, arthritis has been unbearable; This spontaneous case was reported by a patient and describes the occurrence of ARTHRITIS (exacerbated arthritis in knees/Since about 4 to 6 weeks after the booster, arthritis has been unbearable) in a 90-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 046B21A) for COVID-19 prophylaxis.     Previously administered products included for COVID-19 prophylaxis: Moderna COVID-19 Vaccine (Dose no-1,Route of Administration-Intramuscular, lot number- unknown) on 11-Feb-2021, Moderna COVID-19 Vaccine (Dose no-2,Route of Administration-unknown and lot number- 010M20A) on 11-Mar-2021; for Product used for unknown indication: IBUPROFEN (she would take one ibuprofen and be fine). Past adverse reactions to the above products included No adverse event with IBUPROFEN, Moderna COVID-19 Vaccine and Moderna COVID-19 Vaccine. Concurrent medical conditions included Arthritis (exacerbated arthritis).    In November 2021, the patient received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. In November 2021, the patient experienced ARTHRITIS (exacerbated arthritis in knees/Since about 4 to 6 weeks after the booster, arthritis has been unbearable). The patient was treated with Physical therapy for Arthritis. At the time of the report, ARTHRITIS (exacerbated arthritis in knees/Since about 4 to 6 weeks after the booster, arthritis has been unbearable) had not resolved.        For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   No concomitant medication was reported. No Treatment medication was reported. Events musculoskeletal stiffness and back pain are  subsumed under the event arthritis. Patient received the booster and  the second dose in upper arm. Since about 4 to 6 weeks after the booster, arthritis has been unbearable. Reports she is stiff in the morning. patient does a lot of physical activity that she learned at physical therapy, but harder to do now. she is on no daily medications. It was reported that patient saw her doctor on 08-Jun-2022, received a steroid shot in back and her back was feeling better. Patient states the pain is residing, but still very stiff in legs. Shot helped her back a lot.  Company comment:This is a spontaneous case concerning a 90-year-old, female patient with relevant concurrent medical condition of arthritis. Patient has vaccination history of receiving primary series of mRNA-1273 vaccine. Patient experienced the unexpected non-serious AESI event of arthritis (exacerbated arthritis in knees/Since about 4 to 6 weeks after the booster, arthritis has been unbearable). The event occurred approximately 4 to 6 weeks after the booster dose of mRNA-1273 vaccine administration. The event was described as, about 4 to 6 weeks after the booster, arthritis has been unbearable. Patient experienced morning stiffness and reported getting up in the morning is a task. Patient was not treated for arthritis before booster. Before, patient would take one Ibuprofen and be fine. Patient does a lot of physical activity that patient learned at physical therapy, but harder to do now. Patient has no daily medication for arthritis. However, approximately 7 months after receiving the booster dose of mRNA-1273 vaccine, the patient received steroid shot in her back which cause relief. At the time of the report, patient still experience legs stiffness. The patient's age and concurrent medical condition of arthritis remain confounders for the event due to the natural course of the disease. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.    Sender's Comments: This is a spontaneous case concerning a 90-year-old, female patient with relevant concurrent medical condition of arthritis. Patient has vaccination history of receiving primary series of mRNA-1273 vaccine. Patient experienced the unexpected non-serious AESI event of arthritis (exacerbated arthritis in knees/Since about 4 to 6 weeks after the booster, arthritis has been unbearable). The event occurred approximately 4 to 6 weeks after the booster dose of mRNA-1273 vaccine administration. The event was described as, about 4 to 6 weeks after the booster, arthritis has been unbearable. Patient experienced morning stiffness and reported getting up in the morning is a task. Patient was not treated for arthritis before booster. Before, patient would take one Ibuprofen and be fine. Patient does a lot of physical activity that patient learned at physical therapy, but harder to do now. Patient has no daily medication for arthritis. However, approximately 7 months after receiving the booster dose of mRNA-1273 vaccine, the patient received steroid shot in her back which cause relief. At the time of the report, patient still experience legs stiffness. The patient's age and concurrent medical condition of arthritis remain confounders for the event due to the natural course of the disease. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.