16 year-old daughter still had not gotten a regular period/after that she did not get her period; started taking the Progesterone 24Sep2021,She still has not gotten her period yet.I don't know it's been like seven month; This is a spontaneous report received from a contactable reporter(s) (Consumer or other non HCP) from medical information team. The reporter is the parent.  A 16 year-old female patient received bnt162b2 (COMIRNATY), administered in arm right, administration date 29Mar2021 (Lot number: ER8730) at the age of 16 years as dose 1, single for covid-19 immunisation. The patient had no relevant medical history. There were no concomitant medications. The following information was reported: MENSTRUATION IRREGULAR (non-serious) with onset Apr2021, outcome "not recovered", described as "16 year-old daughter still had not gotten a regular period/after that she did not get her period"; MENSTRUATION DELAYED (non-serious) with onset Apr2021, outcome "not recovered", described as "started taking the Progesterone 24Sep2021,She still has not gotten her period yet.I don't know it's been like seven month". The events "16 year-old daughter still had not gotten a regular period/after that she did not get her period" and "started taking the progesterone 24sep2021,she still has not gotten her period yet.i don't know it's been like seven month" were evaluated at the physician office visit. Relevant laboratory tests and procedures are available in the appropriate section. Therapeutic measures were taken as a result of menstruation irregular, menstruation delayed.  Additional information: Caller called on behalf of her daughter who received the first dose of the Pfizer COVID-19 vaccine last 29Mar2021 with Lot number ER8730. Caller stated that from Apr2021 her 16 year-old daughter still had not gotten a regular period and nothing else is different for her daughter except for the vaccine she had. Caller stated that her daughter had been seen by doctors and lab tests results came as normal. Caller also stated that her friend said that the vaccine affects the period or menstrual cycle. Caller also stated that she had seen comments online about the vaccine and about menstrual cycle which matches her daughter's scenario. Caller stated that this had really affected her daughter for the past months. Caller wanted to know if this had been reported as side effect with the Pfizer COVID-19 vaccine. Caller wanted the company to hear her complaint about the Pfizer COVID-19 vaccine relating to the experience of her daughter. Caller stated that this really affected her daughter for the past . She had her vaccine on March and after that she did not get her period; after the vaccine she did not get her period that did not happen, till now her periods are very regular. Doctor gave her progesterone but still, it didn't happen. Lab Test: Reporter stated what is that lab work. Like blood test, yes because she took her to the doctor right, like the in august she took her to Physician, children Physician and they did blood work. Result: Reporter stated everything was normal. Treatment: Reporter stated like last month she took her to gynaecologist because the children doctor could not able to find where the problem was she said go to the gynaecologist so she took her to gynaecologist she also looked into the report she said everything is normal but she gave me progesterone but still it didn't happen. Reporter stated it's been like seven month she was so worried. The doctor gave her daughter Progesterone tablets, 10 tablets. That was 15 days back. She told her to wait 2 more weeks and they will see what happened. Caller states that 2 weeks has gone by, and her daughter still did not get her period. Clarified that her daughter started taking the Progesterone 24Sep2021 and took the medication for 10 days. She still has not gotten her period yet.   No follow-up attempts are possible. No further information is expected.