menstrual cycle prolonged; this is a spontaneous report received from a contactable reporter(s) (consumer or other non hcp) from the regulatory agency. other case identifier(s): gb-mhra-vac-202202122005446830-woz0a (ra), gb-mhra-adr 26598130 (ra). a 39-year-old female patient received bnt162b2 (comirnaty; lot number: unknown) via an unspecified route of administration on an unknown date as a single dose for covid-19 immunisation. medical history was not reported. the patient was not pregnant and was not breastfeeding at the time of this report. last menstrual cycle of the patient was 11feb2022. concomitant medications were not reported. on an unknown date the patient experienced menstrual cycle prolonged; which was reported as serious for being medically significant. the clinical outcome of the event menstrual cycle prolonged was not recovered at the time of this report. no follow-up attempts are possible; information about lot/batch number cannot be obtained. no further information is expected