the booster shot did the same thing. only bleed a week, a full period; This is a spontaneous report received from contactable reporter(s) (Consumer or other non HCP), Program ID. The reporter is the patient.  A 57-year-old female patient received BNT162b2 (BNT162B2), on 04Apr2022 as dose 3 (booster), single (Lot number: FK4843) at the age of 57 years for covid-19 immunisation. The patient's relevant medical history included: "endometriosis" (unspecified if ongoing), notes: she had endometriosis; "diabetes" (unspecified if ongoing), notes: suffers very bad with diabetes. The patient took concomitant medications. Vaccination history included: BNT162b2 (DOSE 1, SINGLE; Lot Number: EWO185), administration date: 06Aug2021, when the patient was 56-year-old, for Covid-19 immunization; BNT162b2 (DOSE 2, SINGLE; Lot Number: EWO185), administration date: 26Aug2021, when the patient was 56-year-old, for COVID-19 immunization, reaction(s): "the 2nd dose made her start her period"; BNT162b2 (DOSE 2, SINGLE; Lot Number: EWO185), administration date: 26Aug2021, when the patient was 56-year-old, for Covid-19 immunization, reaction(s): "she was having heavy periods that were causing her to have cysts", "she was having heavy periods that were causing her to have cysts"; Flu shot, for Covid-19 immunization. The following information was reported: MENSTRUAL DISORDER (non-serious) with onset 2022, outcome "unknown", described as "the booster shot did the same thing. only bleed a week, a full period". Relevant laboratory tests and procedures are available in the appropriate section. Therapeutic measures were taken as a result of menstrual disorder.  Additional information: It was reported that, the 2nd dose made her start her period. She hadn't had a period in 7 or 8 years, it was a full period for 6 weeks. Then the reporter stated the booster shot did the same thing. Only bleed a week, a full period, then it stopped and a week later she bleed the 3rd and 4th week and finally stopped. The reporter stated that she was started on premarin and had bad diabetes, it was so bad they didn't want to knock her out. so they put her on premarin hormone to stop the bleed. Attempted clarification, the reporter stated that she had endometriosis real bad and when she bled, she got blood clots that caused cysts to get on her ovaries. Since then it was not cancer cysts she just had endometriosis bad. The reporter stated that was before starting premarin. She hadn't had a period in 7-8 years but when she took the Pfizer shot she started her period. She gets heavy bleeding, she had endometriosis and she would bleed out and up inside of her and her doctor didn't want her to do that. She gets excessive bleeding. Reporter stated that, she started her period and could have had cysts on her ovaries. She did not know why this happened with a vaccination, it did not cause her to do that with the flu shot. With the booster there was bleeding every other week but for 4 weeks. It was reported that Premarin was started many years ago, 7 or 8 years ago. Reporter stated that she started it 7 or 8 years ago to stop the bleeding. She stated that she was having heavy periods that were causing her to have cysts so she was then put on premarin to stop her menstrual cycle. She had endometriosis and her doctor didn't want her bleeding so she started premarin and it had helped her a lot and stopped her period.; Sender's Comments: Linked Report(s) : US-PFIZER INC-202201140350 same reporter/drug/event, different patient;US-PFIZER INC-202201139735 same patient, different dose and different event.;