instead of having a five day period like I used to, my periods are only 1-3 days; I experienced an 8 hour menstrual period where nothing in my "normal" happened; I only bled during those 8 hours and within four days my body was already on to the next phase of my cycle.; I was passing multiple blood clots ranging from the size of my hand all the way down to a golf ball size; sat on the toilet for hours just uncontrollably passing blood, clots and urine.; This is a spontaneous report received from a contactable reporter(s) (Consumer or other non HCP). The reporter is the patient. Other Case identifier(s): US-PFIZER INC-202101497567 (pfizer).  A 23 year-old female patient (not pregnant) received bnt162b2 (BNT162B2), administered in arm left, administration date 03May2021 17:45 (Lot number: EW0173) at the age of 23 years as dose 1, single for covid-19 immunisation. Relevant medical history included: "Factor V Leiden Mutation Disorder" (unspecified if ongoing), notes: Other medical history: Factor V Leiden Mutation Disorder. There were no concomitant medications. The following information was reported: POLYMENORRHOEA (non-serious) with onset 23May2021 21:00, outcome "recovered with sequelae" (2021), described as "instead of having a five day period like I used to, my periods are only 1-3 days"; MENSTRUAL DISORDER (non-serious) with onset 23May2021 21:00, outcome "recovered with sequelae" (2021), described as "I experienced an 8 hour menstrual period where nothing in my "normal" happened"; MENSTRUATION IRREGULAR (non-serious) with onset 23May2021 21:00, outcome "recovered with sequelae" (2021), described as "I only bled during those 8 hours and within four days my body was already on to the next phase of my cycle."; HEAVY MENSTRUAL BLEEDING (non-serious) with onset 23May2021 21:00, outcome "recovered with sequelae" (2021), described as "I was passing multiple blood clots ranging from the size of my hand all the way down to a golf ball size"; URINE ANALYSIS ABNORMAL (non-serious) with onset 23May2021 21:00, outcome "recovered with sequelae" (2021), described as "sat on the toilet for hours just uncontrollably passing blood, clots and urine.". The events "instead of having a five day period like i used to, my periods are only 1-3 days", "i experienced an 8 hour menstrual period where nothing in my "normal" happened", "i only bled during those 8 hours and within four days my body was already on to the next phase of my cycle.", "i was passing multiple blood clots ranging from the size of my hand all the way down to a golf ball size" and "sat on the toilet for hours just uncontrollably passing blood, clots and urine." were evaluated at the physician office visit. Relevant laboratory tests and procedures are available in the appropriate section. Therapeutic measures were not taken as a result of polymenorrhoea, menstrual disorder, menstruation irregular, heavy menstrual bleeding, urine analysis abnormal.  Additional Information: After getting her first dose, her body went through the same exact physical trauma she gone through when she take the morning pill. She had a blood clotting disorder that doesn't allow her to use female contraceptives (it's called Factor V Leiden Mutation) so after that dose, she experienced an 8 hour menstrual period where nothing in her "normal" happened. she only bled during those 8 hours and within four days her body was already on to the next phase of my cycle. Anyway, she was passing multiple blood clots ranging from the size of her hand all the way down to a golf ball size. she sat on the toilet for hours just uncontrollably passing blood, clots and urine. Anyway, it took about four months for my cycle to get anywhere near her "normal" and now, instead of having a five day period like I used to, my periods are only 1-3 days and her symptoms are also a little different. Although she had only taken plan-b twice in my life, she knew for a fact that this was not normal for her body. It doesn't usually take this long for her to recover from the pill. Before she pieced together that this could've been caused by the vaccine, she visited a Gyno and she was able to confirm that this was not a miscarriage, STD or disease of any kind.  No follow-up attempts are possible. No further information is expected.