This spontaneous case was reported by a nurse and describes the occurrence of POSTURAL ORTHOSTATIC TACHYCARDIA SYNDROME (Postural Orthostatic Tachycardia Syndrome) in an 82-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 3M20A and 027L20A) for COVID-19 vaccination. The patient never tested positive for COVID or diagnosis. The patient's past medical history included Supraventricular tachycardia and Stent placement (2 cardiac stents put in, supraventricular tachycardia prior to the stents) in May 2019. Concurrent medical conditions included Drug allergy (Bactrim allergy), Drug allergy (cardiac medications: Norvasc), Drug allergy (cardiac medications: Ramipril) and Perfume sensitivity. On 06-Jan-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 03-Feb-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 19-Nov-2021, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. In 2022, the patient experienced POSTURAL ORTHOSTATIC TACHYCARDIA SYNDROME (Postural Orthostatic Tachycardia Syndrome). The patient was treated with METOPROLOL on 03-Mar-2022 at a dose of 25 milligram once a day. At the time of the report, POSTURAL ORTHOSTATIC TACHYCARDIA SYNDROME (Postural Orthostatic Tachycardia Syndrome) had not resolved.    DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In November 2021, Blood pressure measurement: 65/49 and at some point in the 50s, BP dropped. In November 2021, Heart rate: 90s. On 24-Aug-2022, Blood pressure measurement: Sitting BP 97/64 and standing BP 86/55. On 24-Aug-2022, Heart rate: sitting pulse rate - 85 and standing pulse rate - 94. For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter considered POSTURAL ORTHOSTATIC TACHYCARDIA SYNDROME (Postural Orthostatic Tachycardia Syndrome) to be related. No vaccines given within 1 month prior to Moderna COVID-19 vaccine. The event cause patient to seek medical care just office visits. The patient went to the emergency room (ER) once but heart rate was already low at the time she got to the ER so there were no findings. The patient had not experienced a similar event in the past. No concomitant information was reported. A retired nurse reported that she had the 1st doses of the Moderna Covid-19 vaccine then followed by the 1st booster dose. Shortly thereafter, around end of Nov 2021, she had fatigue and light headedness which progressed to a blood pressure (BP) problem. She had BPs of 65/49 and at some point in the 50s. She was worked up, her cardiologist had done 2 monitors and they found out that if her heart rate goes to 90s her blood pressure drops. Sometime early this year was diagnosed by her primary physician as having POTS (Postural Orthostatic Tachycardia Syndrome). She said that there was nothing else she could attribute that to except the vaccine. CC: This spontaneous case concerns an 82 year old female patient, with a relevant history of supraventricular tachycardia, who experienced the unexpected, non-serious adverse event of special interest Postural orthostatic tachycardia syndrome, which occurred unknown months after the third dose of mRNA-1273 vaccine administration. The outcome was reported as not resolved. Days after the vaccination of the third dose of mRNA-1273 vaccine, patient had fatigue and light headedness which progressed to a blood pressure (BP) measurements of 65/49 and at some point in the 50s. Patient sought consult with a cardiologist where she was diagnosed with POTS. The patient was treated with metoprolol 25 milligrams once a day. Underlying history of supraventricular tachycardia could be a confounder for the event. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report. This case was linked to US-MODERNATX, INC.-MOD-2022-634805 (E2B Linked Report). Sender's Comments: CC: This spontaneous case concerns an 82 year old female patient, with a relevant history of supraventricular tachycardia, who experienced the unexpected, non-serious adverse event of special interest Postural orthostatic tachycardia syndrome, which occurred unknown months after the third dose of mRNA-1273 vaccine administration. The outcome was reported as not resolved. Days after the vaccination of the third dose of mRNA-1273 vaccine, patient had fatigue and light headedness which progressed to a blood pressure (BP) measurements of 65/49 and at some point in the 50s. Patient sought consult with a cardiologist where she was diagnosed with POTS. The patient was treated with metoprolol 25 milligrams once a day. Underlying history of supraventricular tachycardia could be a confounder for the event. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report. US-MODERNATX, INC.-MOD-2022-634805: Reporter's case (Female Patient).