bone marrow test results showed blood cancer due the low blood platelets; Low blood platelets; This spontaneous case was reported by a consumer and describes the occurrence of LEUKAEMIA (bone marrow test results showed blood cancer due the low blood platelets) and THROMBOCYTOPENIA (Low blood platelets) in an 84-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. M-010M20A) for COVID-19 vaccination.     No Medical History information was reported.    On 08-Feb-2021, the patient received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. In February 2021, the patient experienced LEUKAEMIA (bone marrow test results showed blood cancer due the low blood platelets) (seriousness criterion medically significant) and THROMBOCYTOPENIA (Low blood platelets) (seriousness criterion medically significant). At the time of the report, LEUKAEMIA (bone marrow test results showed blood cancer due the low blood platelets) and THROMBOCYTOPENIA (Low blood platelets) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In February 2021, Platelet count decreased: blood cancer After 2nd one on Feb2021 level drop again after having a bone marrow test results showed patient has blood cancer due to low blood platelets.. In January 2022, Platelet count decreased: 40 the last month 30 and come up to 40 the last month..     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   Concomitant medications were not provided.  It was reported that the patient have a record of all his blood work and patient checked regular due to his cholesterol and find out that after every shot the platelet level drop since first vaccine and after the second one and continue dropping after the booster.  Patient wanted to know whether there was any relation between platelets drop and antibodies and also wanted to know that there was any antibody test to check antibody levels after vaccination. Reporter also mentioned that platelets were dropped 30 and came up to 40 (last month).  Treatment information was not provided.  Company Comment: This spontaneous case concerns an 84-year-old, male patient with no medical history reported, who experienced the unexpected, serious of thrombocytopenia and the unexpected, serious event of leukaemia after administration of the second dose of the Moderna mRNA-1273 vaccine on 08Feb2021. The start dates of the events were not provided. The patient has a previous history of decreased platelet count (unspecified level) after vaccination with the first dose of the Moderna mRNA-1273 vaccine. There were no reported symptoms or treatment provided. After receiving the second dose, the platelet count again decreased (unspecified level). The patient underwent a Bone marrow test which showed that the patient has 'blood cancer due the low blood platelets'. Treatment information was not provided. The outcomes of the events were unknown at the time of the report. It is not clear in the report if the decreased platelet count after the first dose resolved. Further information has been requested to properly assess the case and the rechallenge results. The benefit-risk relationship of the Moderna mRNA-1273 vaccine is not affected by this report.   This case was linked to MOD-2022-474295, MOD-2022-474448 (Patient Link).; Sender's Comments: This spontaneous case concerns an 84-year-old, male patient with no medical history reported, who experienced the unexpected, serious AESI of thrombocytopenia and the unexpected, serious event of leukaemia after administration of the second dose of the Moderna mRNA-1273 vaccine on 08Feb2021. The start dates of the events were not provided. The patient has a previous history of decreased platelet count (unspecified level) after vaccination with the first dose of the Moderna mRNA-1273 vaccine. There were no reported symptoms or treatment provided. After receiving the second dose, the platelet count again decreased (unspecified level). The patient underwent a Bone marrow test which showed that the patient has 'blood cancer due the low blood platelets'. Treatment information was not provided. The outcomes of the events were unknown at the time of the report. It is not clear in the report if the decreased platelet count after the first dose resolved. Further information has been requested to properly assess the case and the rechallenge results. The benefit-risk relationship of the Moderna mRNA-1273 vaccine is not affected by this report.