immunocompromised; Patient was diagnosed with breast cancer in her left breast.; This case was received via an unknown source (no reference has been entered for a health authority or license partner) on 13-Jan-2022 and was forwarded to Moderna on 13-Jan-2022.    This spontaneous case was reported by a consumer and describes the occurrence of BREAST CANCER FEMALE (Patient was diagnosed with breast cancer in her left breast.) and IMMUNODEFICIENCY (immunocompromised) in an 88-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 045C21A and 024M20A) for COVID-19 vaccination.     The patient's past medical history included Breast cancer female NOS (Breast cancer in her right breast (about 45 years ago)) in 1977.   On 21-Jan-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 25-Feb-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 04-Nov-2021, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 12-Jan-2022,  after starting mRNA-1273 (Moderna COVID-19 Vaccine), the patient experienced BREAST CANCER FEMALE (Patient was diagnosed with breast cancer in her left breast.) (seriousness criterion medically significant). On an unknown date, the patient experienced IMMUNODEFICIENCY (immunocompromised) (seriousness criterion medically significant). At the time of the report, BREAST CANCER FEMALE (Patient was diagnosed with breast cancer in her left breast.) and IMMUNODEFICIENCY (immunocompromised) outcome was unknown.        For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   No concomitant medications were mentioned. Patient will be receiving chemo for about 8 months (as treatment).  Daughter asked if patient can get an additional full 3rd dose of the Moderna vaccine.  It was also stated that now the patient was immunocompromised.  This is a spontaneous case concerning a 88-year-old female patient with a medical history of breast cancer female R, who experienced the unexpected events of breast cancer female L and immunodeficiency. The event breast cancer occurred approximately 70 days after the third dose of mRNA  1273 vaccine, while immunodeficiency was experienced on an unknown date. Both the events were reported as medically significant and at the time of report outcome of which is still unknown. The reporter's assessment was not provided. The benefit-risk relationship of the vaccine is not affected by this report.; Sender's Comments: This is a spontaneous case concerning a 88-year-old female patient with a medical history of breast cancer female R, who experienced the unexpected events of breast cancer female L and immunodeficiency. The event breast cancer occurred approximately 70 days after the third dose of mRNA  1273 vaccine, while immunodeficiency was experienced on an unknown date. Both the events were reported as medically significant and at the time of report outcome of which is still unknown. The reporter's assessment was not provided. The benefit-risk relationship of the vaccine is not affected by this report.