At 1440hrs the patient received her 2nd dose of Moderna COVID-19 vaccine.  ? At 1444hrs. patient while in the observation area started to complain that she was feeling warm and was nauseous. Observation staff immediately responded to provide supported care protecting her from falling, preparing area for emergency response. Staff verbally alerted supervising RN to respond. RN performed triage assessment. Clinical presentation was cool, pale, diaphoretic, capillary refill < 3 seconds. Appeared at risk for syncope with repeated spontaneous retching / dry heaves. V/S (Vital Signs): BP (Blood Pressure)- 91/63, P (Pulse)- 94, RR( Respiration Rate)- 20, SPO2 (Spot Oxygen Saturation)- 91% room air. Patient reported PMHx (Past Medical History) of no known allergies, DM II (Type two Diabetes Mellitus) controlled with Metformin / Glucophage and baseline systolic BP 125 mmhg. Reported previous intake as "breakfast before my shift started at 0600" and "I have been snacking on roasted nuts through-out the day with a diet pop." Differential diagnosis of anaphylactic reaction vs. hypoglycemia event due to cardiovascular changes from reported baseline, gastrointestinal and integumentary changes as well as PMHx and intake.  ? At 1446hrs emergency response protocol activated due to differential diagnosis. 4gm Sucrose administered sublingual / buccal. Tolerated well despite continued spontaneous retching / dry heaves. Supplemental oxygen need continuously evaluated, SPO2 91-93%. Hydration and further emergency medications prepared per anaphylaxis protocol.  ? At 1451hrs FD (Fire Department) / EMT responded. V/S: BP- 98/65, P- 80, RR- 20, SPO2- 95% room air. Capillary blood glucose 91 mmol/L. Auscultation of lung sounds and heart tones performed, within normal limits. Spontaneous retching / dry heaves stopped, zero emesis. Patient reported that she had a history of syncopal events with injections. Stating "Since, my last big surgery a couple years ago, I have been fine. I get my blood drawn or whatever, no problem."  ? At 1458hrs EMS arrived. V/S: BP- 101/62, P- 70, RR- 18, SPO2- 95% room air. During continued interview, Patient became more readily responsive to questioning. Integumentary changes improved, dry to palpation and color returned to her face. Patient refused to be transported to the hospital for further evaluation stating, "I don't know why this happened, it just happened so fast. I'm sorry."  ? At 1510hrs EMS and FD / EMT returned care of the patient to clinic staff. She was offered hydration and complex carbohydrates. V/S: BP- 101/62, P- 70, RR- 16,  SPO2- 97% room air. Negative for orthostatic hypotension after standing. The patient was assisted to contact her husband who works in the area. ? At 1540hrs the patient was escorted to her husband nearby. She was observed safely entering the passenger side of the vehicle.  ? At 0800hrs 23 April 2021 supervising RN made contact with the patient who reported that she was "feeling well." None of the symptoms had returned and that her injections site did not have any redness, warmth or swelling. She was encouraged to follow-up with her primary care provider and to contact the local healthcare facility with  any needs further needs.