pneumonia; severe pericarditis; feel unwell; this is a spontaneous report received from a contactable reporter(s) (physician) from the medicines agency () -web. regulatory number: ie-hpra-2022-093016 (hpra). other case identifier(s): ie-hpra-cvarr2022021225780 (hpra). a 41 year-old male patient received bnt162b2 (comirnaty), administration date 22dec2021 (batch/lot number: unknown) as dose 3 (booster), single for covid-19 immunisation. the patient had no relevant medical history. there were no concomitant medications. vaccination history included: comirnaty (dose 1, single), administration date: jun2021, for covid-19 immunisation; comirnaty (dose 2, single, comirnaty double vaccine in jun2021), administration date: jun2021, for covid-19 immunisation. the following information was reported: pneumonia (hospitalization, medically significant) with onset 15jan2022, outcome "unknown", described as "pneumonia"; pericarditis (hospitalization, medically significant) with onset 15jan2022, outcome "unknown", described as "severe pericarditis"; malaise (hospitalization) with onset dec2021, outcome "unknown", described as "feel unwell". the patient was hospitalized for pneumonia, pericarditis, malaise (start date: 26jan2022, hospitalization duration: 13 day(s)). the events "pneumonia", "severe pericarditis" and "feel unwell" were evaluated at the emergency room visit. therapeutic measures were taken as a result of pneumonia, pericarditis, malaise. clinical course: on 22/dec/2021, the patient was vaccinated with the booster dose of comirnaty (batch details: unknown). in dec/2021, 5-7 days post booster, the patient began to feel unwell. the patient was treated with antibiotics and steroids, however, the symptoms continued to get worse. on 16/jan/2022, the patient attended a&e, where they were told they had pneumonia and was discharged with antibiotics. the symptoms got worse, and the patient again attended a&e on 26/jan/2022, where they were admitted as an inpatient for 13 days. the patient reported that pneumonia got worse, and they were told they had severe pericarditis. at the time of reporting, the outcome was unknown. 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) : ie-hpra-2022-093018