anxiety; premenstrual syndrome; breast feeding; breast feeding; irregular periods/cycle has changed, immediately brought forward by 8 days then totally irregular; this is a spontaneous report received from a contactable consumer from the regulatory authority (ra). the reporter is the patient. other case identifier(s): gb-mhra-vac-202202122235131650-jnpno (ra), gb-mhra-adr 26598169 (ra). a 40 year-old female patient (not pregnant) received bnt162b2 (bnt162b2), administration date 23may2021 (batch/lot number: unknown) at the age of 40 years as dose number unknown, single for covid-19 immunisation. relevant medical history included: "breast feeding" (ongoing). the patient's concomitant medications were not reported. the following information was reported: menstruation irregular (medically significant) with onset 23may2021, outcome "not recovered", described as "irregular periods/cycle has changed, immediately brought forward by 8 days then totally irregular"; anxiety (medically significant), outcome "unknown", described as "anxiety"; premenstrual syndrome (medically significant), outcome "unknown", described as "premenstrual syndrome"; off label use (non-serious), product use issue (non-serious), outcome "unknown" and all described as "breast feeding". additional information: the patient menstrual periods became irregular, cycle has changed, immediately brought forward by 8 days then totally irregular. the patient stated, "i've experienced severe pms/anxiety a week before - which i never had before". the patient does not think this reaction occurred as a result of a mistake made in the administration of the vaccine. no follow-up attempts are possible; information about lot/batch number cannot be obtained. no further information is expected.; sender's comments: linked report(s) : gb-pfizer inc-202200311915 baby case