diagnosed with multiple myeloma; This spontaneous case was reported by a patient family member or friend and describes the occurrence of PLASMA CELL MYELOMA (diagnosed with multiple myeloma) in a 72-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 048A21A, 017F21A, 026A21A and 031M20A) for COVID-19 prophylaxis.     Concurrent medical conditions included Multiple myeloma.   On 10-Feb-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 10-Mar-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 24-Oct-2021, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 29-Apr-2022, received fourth dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. In May 2022, the patient experienced PLASMA CELL MYELOMA (diagnosed with multiple myeloma) (seriousness criterion medically significant). At the time of the report, PLASMA CELL MYELOMA (diagnosed with multiple myeloma) had not resolved.        For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter did not provide any causality assessments.   The patient did not receive any other vaccines in the 4 weeks prior to COVID-19 vaccine. No concomitant product was reported. Patient underwent chemotherapy for multiple myeloma and after she had a stem cell transplant on 12-Oct-2022, she also went to the hospital during 3 weeks getting different medications (unspecified) and started with chemotherapy again.  Company comment This is a spontaneous case concerning a 72-year-old female patient, with medical history of multiple myeloma, who experienced the serious (medically significant) event of plasma cell myeloma, which occurred on the next month after the fourth dose of mRNA-1273. It was reported that the patient was diagnosed with multiple myeloma, so she underwent chemotherapy and had a stem cell transplant almost 5 months later. She also went to the hospital during 3 weeks getting different medications (unspecified) and started with chemotherapy again. No further clinical information such as the course of the event, hospitalization, studies performed, treatment details were available for review. The mentioned medical history could be a confounder for the event, although there is no further information about this previous diagnosis of multiple myeloma. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.; Sender's Comments: This is a spontaneous case concerning a 72-year-old female patient, with medical history of multiple myeloma, who experienced the serious (medically significant) event of plasma cell myeloma, which occurred on the next month after the fourth dose of mRNA-1273. It was reported that the patient was diagnosed with multiple myeloma, so she underwent chemotherapy and had a stem cell transplant almost 5 months later. She also went to the hospital during 3 weeks getting different medications (unspecified) and started with chemotherapy again. No further clinical information such as the course of the event, hospitalization, studies performed, treatment details were available for review. The mentioned medical history could be a confounder for the event, although there is no further information about this previous diagnosis of multiple myeloma. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.