Pap showed LSIL, - HPV (Abnormal); Transvaginal ultrasound (29Jun2021): L Ovarian cyst: 3.5 x 3.2 x 3.3 cm.; Estradiol (18Jun2021): 137 pg/ml (high, too high for menopausal female); vaginal bleeding for about five days; The initial safety information received was reporting only non-serious adverse drug reaction. Upon receipt of follow-up information on [02Aug2021], this case now contains serious adverse reaction. Information processed together.  This is a spontaneous report from a contactable physician. A 54-year-old non-pregnant female patient received the second dose of BNT162b2 (PFIZER-BIONTECH COVID-19 mRNA VACCINE, Lot number: EW0150) via intramuscular route in the right deltoid on 01Apr2021 (at the age of 54-years-old) as a single dose for COVID-19 immunization. Medical history breast cancer from Aug2017 and ongoing, bilateral mastectomy and reconstruction in 2018, closed head injury on 02May2018, MTHFR mutation from 21Jul2020 and ongoing, anxiety/depression from 22May2018 and ongoing, prediabetes from 23Oct2017 and ongoing, ongoing allergies, and menopausal. Patient had no known drug allergies. Prior to vaccination, the patient was diagnosed with COVID-19. The patient did not receive any other vaccines within 4 weeks prior to the COVID vaccine. Ongoing concomitant medications included desvenlafaxine succinate monohydrate (PRISTIQ) from 10Aug2020 for anxiety/depression and fluticasone (FLONASE) from 04Oct2017 for allergies. The patient previously received the first dose of BNT162b2 (PFIZER-BIONTECH COVID-19 mRNA VACCINE, Lot: EN6199 ) via intramuscular route in the left deltoid on 09Mar2021 (at the age of 54-years-old) as a single dose for COVID-19 immunization. Six days after her second vaccine (also reported as approximately 4 days later), on 07Apr2021, she experienced period-like vaginal bleeding for about five days while she was on vacation, that was very similar to periods she had in the past. Patient is menopausal and had not had a period in 1.5 years. She has not had any vaginal bleeding since. The adverse event resulted doctor or other healthcare professional office/clinic visit/Physician Office. There was no treatment received for the event. Lab data included FSH test (18Jun2021): 35.2 mIU/mL (Normal high, normal for menopausal female); Estradiol (18Jun2021): 137 pg/ml (high, too high for menopausal female); Progesterone (18Jun2021): <0.5 ng/mL (Norm Low, Normal for menopausal female), Pap (13Jul2021): LSIL - HPV (Abnormal); Endometrial biopsy (13Jul2021): Benign endometrial and endocervical tissue (Normal); Transvaginal ultrasound (29Jun2021): L Ovarian cyst: 3.5 x 3.2 x 3.3 cm. Labs showed menopausal levels of FSH, LH, prolactin and progesterone but high estrogen for a menopausal female. Ultrasound showed left, ovarian cyst. Pap showed LSIL, - HPV and endometrial biopsy negative for cancerous cells. Plan is to recheck pap and hormones in Dec2021 unless her abnormal bleeding restarts. If it restarts, D/C will be done and will check labs sooner. The outcome of the events was unknown. Continuing to monitor. Since the vaccination, the patient had been tested for COVID-19 via nasal swab on 05Apr2021 with result negative. Reporting physician assessed the event as serious for medically significant and considered it was unknown if the Pfizer product had a causal effect to the adverse event. Patient is being evaluated by OBGYN currently.   Follow-up attempts are completed. No further information is expected.; Sender's Comments: The causal association of the event vaginal bleeding in relation to suspected drug BNT162b2 (PFIZER-BIONTECH COVID-19 mRNA VACCINE cannot be totally excluded.  The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to regulatory authorities, Ethics Committees, and Investigators, as appropriate