Moderna COVID-19 Vaccine Reaction Report   HPI:  Reaction to vaccine administered on 12/29/2020. Moderna / 026L20A  26 year old Caucasian female with no past medical history. Healthy, physically active (marathon runner, triathlete). Occupation as a Physician Assistant. No known history of having COVID. Had IgG antibody test on 12/16/2020 at PCP office which was negative for antibodies. Has never been tested acutely for COVID. No known COVID exposure within the last 14 days. No fever, cough, or chills within the last 6 months. No history of anaphylaxis. UTD on all vaccines, including influenza and Tdap/Pertussis. No history of allergic reaction to vaccines or food. Only medication allergy was Penicillin (rash at 2 years old).   Took 500mg Tylenol (prophylactically for soreness after vaccine) and vitamin D supplement along with breakfast around 10am before going to get the vaccine. I was feeling well that morning and did my normal morning workout.   Vaccine administered around 11am. Within 3-5 mins, reaction started with flushing, shaking of the upper and lower extremities, and feeling weak and faint. After laying down, the shaking and flushing continued and progressed. My teeth started chattering and my jaw and neck started to feel stiff. Was given 50mg of liquid benadryl around 11:20am. Within 20-30 mins, symptoms were improving, but then, symptoms returned (around 20 minutes after the first wave resolved). The symptoms were worse in the second episode, with full body shaking, stiffness of neck, teeth chattering and jaw starting to clench. Became pale and flushed. No difficulty breathing or SOB, although my throat felt a little tight. Had difficulty speaking due to throat / jaw tightness. Unable to stand without assistance due to leg tremors/shaking/weakness. Was given 6mL Decadron IM around 12:20pm. Within 20-30 mins of Decadron administration, symptoms started to improve.   I was transported to the ER by ambulance and was stable. Still felt shaky and weak. Was evaluated and given 40mg Pepcid. Symptoms continued to improve. Was observed for around 2 hours. Was discharged and sent home. Took 25mg benadryl as recommended at 4:45pm, ad 500mg Tylenol.   Around 7:45pm (after eating supper), I started to feel a little flushed/faint again, and was visibly pale. Started to have mild throat/neck tightness and slight tremors in hands, but no difficulty breathing or airway swelling. No rash. Took 25 mg Benadryl at 8pm and drank plenty of fluids. Started to experience tingling in both thighs, which later moved to both calves which lasted around 8 hours. No hand or feet tingling. Tingling resolved in the morning by 7am. No leg or arm weakness. Next morning, I was feeling much better. Only symptoms in the morning were mild fatigue and mild soreness at the injection site on the left deltoid.      PE:  Vitals: BP slightly low ranging from 96/68 to 106/70. HR stable at around 50-60bpm. 02 sat 99%. RR around 18-20. Temp around 98 degrees F. BMI 21.    Skin: Skin flushed but no hives or rash on the body or at the injection site. Mild palmar diaphoresis. No LAD.  Lungs: Breathing unlabored. No throat, tongue, or tonsillar swelling. Lungs CTAB.  Heart: RRR  Neuro: Pupils equal. Hyper-reflexia of the bilateral lower extremities.    PMHx: No past medical history / comorbidities.  Last menstrual cycle 12/1/2020. No chance of pregnancy.    Family history: No family history of allergic reactions to vaccines or food. No family history of anaphylaxis.     Medications: Vitamin D supplement (2000 IU / day)  Multivitamin    Allergies: Penicillin (rash when given at 2 years of age)