Muscle pain; Chills; Fever; White Blood Cell Count low; Hematocrit low; Hemoglobin low; This spontaneous case was reported by a consumer (subsequently medically confirmed) and describes the occurrence of WHITE BLOOD CELL COUNT DECREASED (White Blood Cell Count low), HAEMATOCRIT DECREASED (Hematocrit low) and HAEMOGLOBIN DECREASED (Hemoglobin low) in a 37-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 028L20A and 039K20-2A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     No Medical History information was reported.   On 27-Dec-2020, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 24-Jan-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. In February 2021, the patient experienced WHITE BLOOD CELL COUNT DECREASED (White Blood Cell Count low) (seriousness criterion medically significant), HAEMATOCRIT DECREASED (Hematocrit low) (seriousness criterion medically significant) and HAEMOGLOBIN DECREASED (Hemoglobin low) (seriousness criterion medically significant). On an unknown date, the patient experienced MYALGIA (Muscle pain), CHILLS (Chills) and PYREXIA (Fever). At the time of the report, WHITE BLOOD CELL COUNT DECREASED (White Blood Cell Count low) had not resolved and HAEMATOCRIT DECREASED (Hematocrit low), HAEMOGLOBIN DECREASED (Hemoglobin low), MYALGIA (Muscle pain), CHILLS (Chills) and PYREXIA (Fever) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In 2021, Biopsy bone marrow: normal (normal) normal. In 2021, Haematocrit: low (Low) Low. In 2021, Haemoglobin: low (Low) Low. In 2021, White blood cell count: low (Low) Low. In September 2021, Vitamin B12: normal (normal) Normal. In September 2021, White blood cell count: low (Low) White Blood Cell count remained low.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter did not provide any causality assessments.   Concomitant medication information was not provided by the reporter.  Treatment information was not provided by the reporter.  Two weeks post vaccine and patient's white blood cell count, hematocrit, and hemoglobin were all low.  Patient was sent to a hematologist on 16 Sep 2021 and patient submitted monthly blood draws. Patient's white blood cell count remained low. The Hematologist did more blood work and found that patient had normal levels of vitamin B12.  The hematologist also ordered a bone marrow biopsy. Cancer was ruled out.  A Toxin or a medication was the suspected cause of my issue. Patient's white blood cell count had not been above 2000 since the patient received the vaccine.  Prior to this bloodwork patient had always been normal.  Company Comment:  This case concerns a 37 year-old female patient with no relevant history reported, who experienced the unexpected serious events of White blood cell count decreased, Hematocrit decreased and Haemoglobin decreased. These events occurred 2 weeks after the administration of the second dose of mRNA-1273 vaccine. Rechallenge is not applicable, since no further dosing is expected. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report   This case was linked to MOD-2021-339166 (Patient Link).; Sender's Comments: This case concerns a 37 year-old female patient with no relevant history reported, who experienced the unexpected serious events of White blood cell count decreased, Hematocrit decreased and Haemoglobin decreased. These events occurred 2 weeks after the administration of the second dose of mRNA-1273 vaccine. Rechallenge is not applicable, since no further dosing is expected. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report