after the second dose of pfizer vaccine made on 05nov2021 my cycle lasts a week with a very abundant flow, unlike before i had a regular flow lasting 3 days; this is a spontaneous report received from a contactable reporter(s) (consumer or other non hcp) from the regulatory authority-web. regulatory number: it-minisal02-842699. a 39 year-old female patient received bnt162b2 (comirnaty), administered in arm left, administration date 05nov2021 (batch/lot number: unknown) as dose 2, single for covid-19 immunisation. the patient's relevant medical history and concomitant medications were not reported. vaccination history included: covid-19 vaccine (dose 1, manufacturer unknown), for covid-19 immunisation. the following information was reported: heavy menstrual bleeding (disability) with onset 06nov2021, outcome "unknown", described as "after the second dose of pfizer vaccine made on 05nov2021 my cycle lasts a week with a very abundant flow, unlike before i had a regular flow lasting 3 days". clinical course: impact on quality of life (10/10). no follow-up attempts are possible; information about lot/batch number cannot be obtained. no further information is expected