have very large menstrual clots/ large clots "one was the the size of a mouse"/ flowed abnormally; menstruate 2 days afterward/ had 4 periods within a 2 month period; gets exhausting being on her period all of the time,; This is a spontaneous report received from a contactable consumer (patient). This consumer reported events after the first and second dose of vaccine. This is the second of two reports (dose 2). A 38-year-old female patient received bnt162b2 (COMIRNATY), administered in right arm on 17Apr2021 (at the age of 38-year-old) as dose 2, single for COVID-19 immunization. The patient's medical history and family medical history were reported as none. The patient's concomitant medications were not reported. Adverse events following prior vaccinations were reported as none. Caller stated it just hurt when they stuck it in her behind when she was a kid, she couldn't remember the name. The patient previously received bnt162b2 (COMIRNATY) via unknown route of administration in right arm on unspecified date in Mar2021 (at the age of 38-year-old) as dose 1, single for COVID-19 immunisation and she experienced spotting/ spotted a little. The patient had not received other vaccine within 4 weeks prior vaccinations. No additional vaccines were administered on same date of the Pfizer suspect. It was reported that after the second dose of the Pfizer COVID-19 shot her body started to menstruate and she had very large menstrual clots. She had flowed abnormally and ended up having 4 periods in the first two months after the second dose of Pfizer's COVID 19 vaccine. She would like any information they had and any studies showing what she could expect in the future from this vaccine. Caller (patient) added that she had done different tests (mammogram, ultrasound of ovaries, diabetes test and a full panel of tests and she was fine except for the Pfizer COVID-19 shot. She added that the blood clot she had was the size of a mouse. She stated that it happened within a week from the Pfizer COVID-19 shot (19Apr2021) and has had nothing like that since she was 13 years old. She had already consulted with a gynecologist. Additionally, it was reported that after her second dose she started to menstruate 2 days afterward even though she had just gotten off of her period. She also reported large clots one was the size of a mouse. Additionally, she had 4 periods within a 2-month period. She had an ultrasound of the ovaries and cervix all came back normal. She stated the problems with menstruation was ongoing but improved by being more liquid with not as many big clots, but she still didn't know when one's going to come. She wanted to know how long she should expect this to last and when she would return back to normal. She also asked what makes the information anecdotal, how are adverse events evaluated for causation and what tests could her health care professional (HCP) do. Caller stated they did an ultrasound of her ovaries and cervix and it was normal. Caller stated they also did a mammogram and thyroid test and they were normal and a diabetes test that was normal and a full work up panel and she was not anemic. Caller stated everything was normal, except the Pfizer shot. Caller stated she was very regular and she had just gotten off of her period just before the second dose. Caller stated she was super regular and she started again 6 days later after her period stopped. Caller stated it had improved, it was more liquid, and there was not as many big clots, it was just more liquid now, it was very odd. Caller stated she didn't flow over one pad an hour and if she would, she would contact her doctor. Caller stated she usually flows a pad an hour and half per pad, she monitored it. Caller stated it gets exhausting being on her period all of the time, she had to tell her kids, mommy needed a nap. Caller stated she was afraid she will get her period out of the blue. The onset date of events was reported as 19Apr2021. The patient had not received treatment due to the events. The events required physician office visit to primary care physician (PCP) and obstetrician-gynecologist (OBGYN). The outcome of the events was resolving.  The lot number for the vaccine, BNT162B2, was not provided and will be requested during follow-up.; Sender's Comments: Linked Report(s) : PFIZER INC-202101427343 same patient/drug, different events/dosed