Thyroiditis subacute/Viral thyroiditis; This is a spontaneous report from a non-contactable consumer. Out of 29 cases, 18 cases were reported for Pfizer. This case belong patient 18. A female patient of an unspecified age received bnt162b2 (PFIZER-BIONTECH COVID-19 VACCINE, Solution for injection, Batch/Lot Number was not reported, Expiry date: unknown), via an unspecified route of administration on an unspecified date as DOSE NUMBER UNKNOWN, SINGLE for covid-19 immunisation. The patient medical history was not reported. Concomitant medication(s) included ciprofloxacin. It was reported, 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). Patients experiencing SAT following vaccination were mainly female (n=24 83%) 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. Furthermore, in the recent scientific literature a series of case reports of patients developing SAT associated with COVID-19 infections was published14 to 21. Six of the eight published reports concern female patients14 to 16,19 to 21. In the current case series, three of the 16 authorized COVID-19 vaccines were reported as suspected. However, one case (case 18) reported a viral thyroiditis without further specification. The only available information was that the patient was not tested positive for COVID-19. Another two cases may represent confounders: the patient in case 16 was reported to receive concomitant eculizumab treatment in course of a clinical trial. Eculizumab potentially increases the risk for infections favouring the occurrence of SAT. Subacute thyroiditis (SAT) is an inflammatory disease of the thyroid caused by viral infections or autoimmune reactions. Its reported incidence was 12.1 cases/100,000 person years with a higher incidence in females than males (19.1 vs 4.1 cases/100,000 person years) between 1970 and 19971. However, no recent information about SATs incidence is available. Two of the cases reported the occurrence of SAT in young female patients (25 and 28 years old) following seasonal influenza vaccination10,11. The fourth case report described a previously healthy 36-year-old female patient who presented with clinical symptoms of thyrotoxicosis after having received H1N1 influenza vaccination one month prior to presentation13. Though there is not much evidence of SAT following immunization in general, a series of case reports on patients developing SAT in association with COVID-19 infection can be found in the recent scientific literature14 to 21. Inflammatory response, apoptosis, and local damage, direct viral replication, interaction with thyroidal ACE2 receptors, and a potential central mechanism with low TSH level possibly secondary to hypothalamus-pituitary dysfunction have been discussed as potential mechanisms for COVID-19- induced SAT20. The patient's hospitalization was prolonged as a result of thyroiditis subacute/viral thyroiditis. The patient underwent lab tests and procedures which included plasma viscosity: raised, thyroid function test: abnormal on an unspecified date. Outcome of the event was not recovered.    No follow-up attempts are possible; information about lot/batch number cannot be obtained.