I developed an irregular menstraul cycle.; It was much longer than it usually is and lasted for 9 days; She is getting her period every 6 days. Since August, she's had 8 periods; This is a spontaneous report received from a contactable reporter(s) (Consumer or other non HCP) from medical information team for a Pfizer sponsored program (005570). The reporter is the patient.  A 22 year-old female patient received bnt162b2 (BNT162B2), administration date Jun2021 (Batch/Lot number: unknown) as dose 1, single and administration date Jul2021 (Batch/Lot number: unknown) as dose 2, single for covid-19 immunisation. The patient's relevant medical history and concomitant medications were not reported. The following information was reported: MENSTRUAL DISORDER (non-serious) with onset 01Aug2021, outcome "unknown", described as "I developed an irregular menstraul cycle."; OLIGOMENORRHOEA (non-serious) with onset Aug2021, outcome "unknown", described as "It was much longer than it usually is and lasted for 9 days"; HEAVY MENSTRUAL BLEEDING (non-serious) with onset Aug2021, outcome "unknown", described as "She is getting her period every 6 days. Since August, she's had 8 periods".  Additional information: The patient took the Pfizer BioNTech Covid 19 vaccine in Jun2021 and Jul2021 and starting in Aug2021 she developed irregular menstrual cycles. The reporter stated that her whole life she has been exact on her cycle and after the vaccine suddenly she was getting her period every 6 days, that since Aug2021 she has had 6 periods. The patient went to her doctor to rule out anything else and was told that it was 100% vaccine related. The patient stated that it had been 7 or 8 periods since Aug2021. The patient stated that she got the vaccine in Jun2021 and Jul2021 and starting 01Aug2021 she got her period and it was much longer than it usually was and lasted for 9 days. Stated she usually gets it for 3-4 days. The patient concerned was about 8 days later she got it again for 5 days, then starting Sep2021 she got it again from 03Sep2021-07Sep2021 and from 13Sep2021-22Sep2021 and then again 29Sep2021-5Oct2021. The patient stated that it was weird these are much longer than her usual periods and way more frequent. She just got it again 12Oct2021 and honestly she was fed up with it, she was running out of product to use every day, she was always running out.  The patient stated that she did go to the doctor, and they said it was 100% related to the vaccine. She went a month ago and was seen and got it 4 times. The patient stated that it seems concerning to her that it's not listed in side effects on anything because she does know some people that experienced menstrual irregularities from the vaccine. The patient asked would it be possible for Pfizer to send her tampons; she can't keep going and buying them. The patient stated that there have been anecdotal and media reports of irregular menstrual cycles, including skipped periods, prolonged periods, spotting after COVID-19 vaccines in adults and similar changes in menstrual cycles have been reported after COVID-19 infection. This was not surprising because infections, immune reactions, and fevers can cause short-term, self-limited changes in cycles. However, further studies are needed to verify these changes in people who have received COVID-19 vaccines.  No follow-up attempts are possible; information about lot/batch number cannot be obtained. No further information is expected.