Patient had extreme migraine during this time; I have a severe adverse reaction to the vaccine/Something that is life changing; Patient also had dizziness; Bad headache; Patient didn't receive second shot/More than 42 days past for second vaccination; Severe cramping; Huge blood clots the size of my hand/Patient continued to have blood clots for a week and then it stopped; I've had abnormal uterine bleeding since I got the vaccine / and it was odd to randomly start again like that./Two weeks after it stopped, the menstrual cycle started again and it didn't stop for a month; Huge blood clots the size of my hand  on her menstrual cycle/Patient continued to have blood clots for a week and then it stopped; This spontaneous case was reported by a consumer (subsequently medically confirmed) and describes the occurrence of THROMBOSIS (Huge blood clots the size of my hand/Patient continued to have blood clots for a week and then it stopped) in a 35-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 038B21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     No Medical History information was reported.    On 09-Apr-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 09-Apr-2021,  after starting mRNA-1273 (Moderna COVID-19 Vaccine), the patient experienced HEADACHE (Bad headache) and PRODUCT DOSE OMISSION ISSUE (Patient didn't receive second shot/More than 42 days past for second vaccination). In April 2021, the patient experienced THROMBOSIS (Huge blood clots the size of my hand/Patient continued to have blood clots for a week and then it stopped) (seriousness criterion medically significant), MENSTRUAL DISORDER (Huge blood clots the size of my hand  on her menstrual cycle/Patient continued to have blood clots for a week and then it stopped), ABDOMINAL PAIN (Severe cramping) and ABNORMAL UTERINE BLEEDING (I've had abnormal uterine bleeding since I got the vaccine / and it was odd to randomly start again like that./Two weeks after it stopped, the menstrual cycle started again and it didn't stop for a month). On an unknown date, the patient experienced MIGRAINE (Patient had extreme migraine during this time), VACCINATION COMPLICATION (I have a severe adverse reaction to the vaccine/Something that is life changing) and DIZZINESS (Patient also had dizziness). On 09-Apr-2021, PRODUCT DOSE OMISSION ISSUE (Patient didn't receive second shot/More than 42 days past for second vaccination) had resolved. At the time of the report, THROMBOSIS (Huge blood clots the size of my hand/Patient continued to have blood clots for a week and then it stopped), MENSTRUAL DISORDER (Huge blood clots the size of my hand  on her menstrual cycle/Patient continued to have blood clots for a week and then it stopped), MIGRAINE (Patient had extreme migraine during this time) and ABNORMAL UTERINE BLEEDING (I've had abnormal uterine bleeding since I got the vaccine / and it was odd to randomly start again like that./Two weeks after it stopped, the menstrual cycle started again and it didn't stop for a month) had not resolved, ABDOMINAL PAIN (Severe cramping), VACCINATION COMPLICATION (I have a severe adverse reaction to the vaccine/Something that is life changing) and HEADACHE (Bad headache) outcome was unknown and DIZZINESS (Patient also had dizziness) had resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 13-Apr-2021, Fibrin D dimer: positive (Positive) Positive. On 13-Apr-2021, X-ray: normal (normal) X-ray of the chest and brain and they didn't see any blood clots. In April 2021, Pregnancy test: negative (Negative) Patient tested negative for a pregnancy. On an unknown date, Biopsy: normal (normal) Did a biopsy of ovaries and everything was fine. On an unknown date, Ultrasound scan: normal (normal) They made an ultrasound as well, and didn't see anything.     The action taken with mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) was unknown.       Treatment included  birth control pills for hormone medication to restart cycle.  Patient visited an Obstetrics and gynecology (OB Gyn). Doctor prescribed medication to make it stop, and to restart everything (the cycle). It stopped for seven days, and after that patient continued to bleed, and it did not stop. So doctor had to then put her on birth control that patient needs to take every day. The options at the moment was to continue with birth control or to have a hysterectomy.   Most recent FOLLOW-UP information incorporated above includes: On 26-Sep-2021: Follow-up information included reporter details, lab tests, suspect product details, treatment, and new events. Case upgraded to serious.; Sender's Comments: This is a case of missed dose concerning a 35-year-old female patient with no reported medical history who experienced the unexpected events of abnormal uterine bleeding and thrombosis.  The events occurred after an unspecified period in the same month of administration of first dose of mRNA-1273 (Spikevax). The re-challenge was unknown dates of event onset were not disclosed. Causality for the reported events was not provided by the reporter. The benefit-risk relationship of the vaccine is not affected by this report. Thrombosis is an adverse event of special interest and uterine hemorrhage is an important medical event