maternal exposure during breast feeding; maternal exposure during breast feeding; this is a solicited report received from a contactable reporter(s) (consumer or other non hcp) from the regulatory agency for a sponsored program. regulatory number: gb-mhra-ycvm-202106280855089900-p2q4s. other case identifier(s): gb-mhra-adr 26630205, gb-pfizer inc-202200328147 (mother/baby case). a 27 year-old female patient (not pregnant) received bnt162b2 (bnt162b2), administration date 23jun2021 (lot number: fc9001) as dose 1, 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: off label use (medically significant), product use issue (medically significant) and all described as "maternal exposure during breast feeding". clinical course: patient has not had symptoms associated with covid-19 and not had a covid-19 test. patient was not pregnant. patient last menstrual period date 08nov2020. since the vaccination, patient has not tested for covid-19. patient was not enrolled in clinical trial. the reporter assessment of the causal relationship of the events with the suspect product (comirnaty) was not provided at the time of this report. since no determination has been received, the case is managed based the company causality assessment. no follow-up attempts are possible. no further information is expected.; sender's comments: based on the information in the case report, a possible causal relationship between the reported events and the suspect drug bnt162b2 cannot be completely excluded. the impact of this report on the benefit/risk profile of the pfizer drug is evaluated as part of pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to regulatory authorities, ethics committees and investigators, as appropriate