off label use; interchange of vaccine product; vertigo; chills; fatigue; headache; pain in arm; this is a spontaneous report received from a contactable reporter (consumer or other non hcp) from the regulatory authority. regulatory number: gb-mhra-webcovid-202202191122538420-ppoxc. other case identifier: gb-mhra-adr 26625653. a 52-year-old female patient (not pregnant) received bnt162b2 (comirnaty) (batch/lot number: unknown) as dose 3 (booster), single for covid-19 immunisation. relevant medical history included: "covid-19", start date: 24dec2021, stop date: 10jan2022; "hormone replacement therapy" (unspecified if ongoing). concomitant medication(s) included: oestrogel taken for hormone replacement therapy, start date: 10sep2021. vaccination history included: covid-19 vaccine astrazeneca (dose 1, single), administration date: 19mar2021, for covid-19 immunisation; covid-19 vaccine astrazeneca (dose 2, single), administration date: 07jun2021, for covid-19 immunisation. the following information was reported: off label use (medically significant), outcome "unknown", described as "off label use"; interchange of vaccine products (medically significant), outcome "unknown", described as "interchange of vaccine product"; headache (medically significant) with onset 16feb2022, outcome "not recovered", described as "headache"; pain in extremity (medically significant) with onset 16feb2022, outcome "not recovered", described as "pain in arm"; chills (medically significant) with onset 17feb2022, outcome "recovered" (18feb2022), described as "chills"; fatigue (medically significant) with onset 17feb2022, outcome "recovering", described as "fatigue"; vertigo (medically significant) with onset 19feb2022, outcome "not recovered", described as "vertigo". the patient underwent the following laboratory tests and procedures: covid-19 virus test: (26dec2021) positive. additional information: patient is not currently breastfeeding. patient has not tested positive for covid-19 since having the vaccine. patient is not enrolled in clinical trial. no follow-up attempts are possible; information about lot/batch number cannot be obtained. no further information is expected