oligomenorrhoea/menstrual cycle prolonged/period cycle longer; heavy menstrual bleeding; heavy bleeding and clots; menstrual irregularity; this is a spontaneous report received from a contactable reporter(s) (consumer or other non hcp) from the regulatory authority other case identifier(s): gb-mhra-vac-202202121539034820-64gtq. a female patient received bnt162b2 (bnt162b2), administration date 12may2021 (lot number: et8885) as dose number unknown, single for covid-19 immunisation. the patient's relevant medical history and concomitant medications were not reported. the following information was reported: menstruation irregular (medically significant) with onset 01jun2021, outcome "not recovered", described as "menstrual irregularity"; oligomenorrhoea (medically significant), outcome "unknown", described as "oligomenorrhoea/menstrual cycle prolonged/period cycle longer"; heavy menstrual bleeding (medically significant), outcome "unknown", described as "heavy menstrual bleeding"; menstrual disorder (medically significant), outcome "unknown", described as "heavy bleeding and clots". additional information: the patient did not think this reaction occurred as a result of a mistake made in the administration of the vaccine. no follow-up attempts are possible. no further information is expected