Thyroiditis subacute; This is a spontaneous report from a contactable consumer. This case belong patient 27. A 47-year-old female patient received BNT162B2 (PFIZER-BIONTECH COVID-19 VACCINE, Formulation: Solution for injection, Batch/Lot Number: unknown) via an unspecified route of administration on an unspecified date as single dose for COVID-19 immunization. Medical history and concomitant medications were not reported. The patient experienced subacute thyroiditis on unspecified date. Calculated Time-to-onset (TTO): 0 days. It was reported that 29 reports of SAT (Agency preferred term (PT): thyroiditis subacute) following immunization with the novel COVID-19 vaccines. Furthermore, Agency comprised 50 cases reporting the PT autoimmune thyroiditis and another 50 cases reporting the PT thyroiditis following COVID-19 vaccination up to 8 June 2021. In 30 of the 50 cases reporting the PT autoimmune thyroiditis patients were described to suffer underlying Hashimoto's thyroiditis flaring up after the vaccination. The following analysis will focus on the cases reporting the Agency PT thyroiditis subacute as it was the only PT found to be disproportionately reported. In-depth analysis of the other mentioned PTs can be made available on demand. Cases reporting SAT were sent from nine countries. Countries contributing most reports were the (Withheld) (n=9), (Withheld) (n=6), and (Withheld) (n=4). Eighteen (62%) of the 29 reports were for the Pfizer/BioNTech mRNA vaccine, five for the Moderna mRNA vaccine, and six for the AstraZeneca adenovirus vector-based vaccine. Cases were mostly classified as non-serious (62%). In the 11 serious cases, two reported caused or prolonged hospitalization and the other nine medically important conditions as the seriousness criteria. Information on the dose number was available in 19 cases. In 11 cases the SAT occurred after administration of the first dose and in nine cases after the second dose. Time-to-onset (TTO) was observed to be in median three days after the second dose (ranging from 0 to 60 days) compared to a median TTO of six days after the first dose (ranging from 0 to 26 days). In one case (case 8), reporting the SAT onset after the second dose, it was mentioned that the patient experienced SAT already after the first dose and that symptoms recurred with the second (positive rechallenge). TTO in this case was reported as one day after vaccination with the second dose. Furthermore, this patient seemed to have an underlying thyroid disorder. It was reported that the symptoms of SAT resolved when she stopped her ''thyroid medication'' Since it was not specified what kind of medication the patient was taking, it is not possible to conclude whether it was underlying hyper- or hypothyroidism. Patients experiencing SAT following vaccination were mainly female (n=24; 83%) and five patients were male (17%). Patients' age was reported in 28 cases resulting in a median age of 45 years (range 18 to 67 years). The most frequently co-reported terms were pyrexia (n=7), lymphadenopathy and neck pain (each n=4), and blood TSH decreased, headache, hyperthyroidism, iodine uptake decreased, tachycardia, and thyroxine free decreased (each n=3). The radioactive iodine uptake (RAIU) test is a reliable test to differentiate between causes of hyperthyroidism. Low uptake suggests thyroiditis and high uptake suggests Grave's disease6. In the current case series, RAIU was performed in three cases confirming the diagnosis of SAT (cases 5, 23, and 26). In five reports (17%) cardiac reactions, such as tachycardia and palpitations, and in three cases (10%) hyperthyroidism were co-reported. Another eight cases contained non-specific reaction terms, such as pyrexia (n=7), neck pain (n=4), headache (n=3), and arthralgia (n=2). Information about the outcome was available in 22 cases. The outcome was reported as 'not recovered' at the time of reporting in 12 cases (41%), in eight cases it was reported as 'recovered' and in the remaining two cases the outcome was unknown. In seven cases (24%) patients reportedly received pharmacotherapy. In six of the cases corticosteroids (prednisone or dexamethasone) were used to treat SAT and in the remaining case the patient was planned to start antibiotic therapy. Information about the outcome was available in five of these cases. In two cases the patients were reported to have recovered, in one case the patient was recovering at the time of reporting and in the remaining two cases the outcome was reported as not recovered at the time of reporting, but in one of those cases (case 16) the patient was reported to respond to prednisone treatment. Except for case 8, a second patient (case 2) was reported to have an underlying thyroid disorder (autoimmune thyroiditis). Furthermore, the patient in case 13 was reported to have complained about a swelling at the right side of her neck with pain radiating to the right ear for one month prior to vaccination. She was furthermore reported to have underlying normocytic anemia. However, an SAT was suspected and successfully treated with NSAIDs and corticosteroids. In a third case (case 23) the patient was found to have had a past COVID-19 infection (diagnosed via an antibody test) but an acute infection was excluded via antigen testing. Seriousness criteria reported as intervention/medically important, hospitalization required and hospitalization prolonged. The outcome of event was not recovered at the time of report.  No follow-up attempts are possible; information about lot/batch number cannot be obtained. No further information is expected.