giant clots / clots are sizes of a large pickle; has tested positive for Covid; has tested positive for Covid; really heavy period; irregular period, really heavy 12-13 days after the end of her period; arm hurting /sore arm; arm swelled up; lump; bad cramps; This is a spontaneous report received from contactable reporter(s) (Consumer or other non HCP) from medical information team and product quality group. The reporter is the parent.  A 11 year-old female patient received bnt162b2 (COMIRNATY), administered in arm left, administration date 07Nov2021 (Lot number: F65127) at the age of 11 years as dose 1, single for covid-19 immunisation; influenza vaccine (FLU), administered in arm left, administration date 10Nov2021 (Batch/Lot number: unknown) for immunisation. The patient had no relevant medical history. The patient's relevant medical history and concomitant medications were not reported. The following information was reported: THROMBOSIS (medically significant) with onset 23Nov2021 21:00, outcome "not recovered", described as "giant clots / clots are sizes of a large pickle"; DRUG INEFFECTIVE (medically significant), COVID-19 (medically significant) all with onset 23Nov2021, outcome "unknown" and all described as "has tested positive for Covid"; MENSTRUATION IRREGULAR (non-serious) with onset 22Nov2021, outcome "unknown", described as "irregular period, really heavy 12-13 days after the end of her period"; HEAVY MENSTRUAL BLEEDING (non-serious) with onset 22Nov2021 23:30, outcome "not recovered", described as "really heavy period"; DYSMENORRHOEA (non-serious) with onset Nov2021, outcome "unknown", described as "bad cramps"; PAIN IN EXTREMITY (non-serious) with onset 10Nov2021, outcome "recovered" (Nov2021), described as "arm hurting /sore arm"; PERIPHERAL SWELLING (non-serious) with onset 10Nov2021, outcome "recovered" (Nov2021), described as "arm swelled up"; NODULE (non-serious) with onset 10Nov2021, outcome "recovered" (Nov2021), described as "lump". The events "giant clots / clots are sizes of a large pickle", "irregular period, really heavy 12-13 days after the end of her period", "really heavy period" and "bad cramps" were evaluated at the physician office visit. The patient underwent the following laboratory tests and procedures: pyrexia: (23Nov2021) 102.8; (23Nov2021) 101; (25Nov2021) 99; sars-cov-2 test: (23Nov2021) positive; (24Nov2021) positive. Therapeutic measures were taken as a result of thrombosis, covid-19, menstruation irregular, heavy menstrual bleeding, dysmenorrhoea. Vaccination Facility Type was reported as Pharmacy. No vaccine was received 4 weeks prior to the first administration date of the suspect vaccine, flu vaccine was administered 3 days afterwards. The patient had no relevant family medical history. It was reported that, no predisposing factors involved. The patient had her period a couple of times, she just got it in on an unspecified date in Aug2021. The caller was giving her daughter ibuprofen either 200 mg or 400 mg and Tylenol 500 mg for the fever and for the cramps. Caller says that the ibuprofen is not handy at the moment. The pediatrician gave her a birth control pill, Provera, to stop the bleeding, which it did. When she had started the Provera she continued to have clots until Friday. On first day that the Provera had started working and takes the Provera at 19:15 and she will wake up and her pad was much, much better and ever since the clots started getting better, at 2:00 she gets horrible cramps and has the heavy bleeding again. So then for about 5 to 6 hours it was worse. The patient had nasal swabs performed.  No follow-up attempts are possible. No?further?information?is expected.