89 yo woman, very reliable historian, in generally good health except for some hypertension, high cholesterol but clear arteries (other than a widow-maker lesion found about 15 yrs ago from mild ssx and was by-passed succesfully) and an osteoporosis-related mid-thoracic vertebral fracture (3 years ago) causing a dowager?s hump becoming more prominent over time.   BPs controlled at 120/75 on enalapril 2.5 mg po q.am.  No other medications. PMH?at age 75 had successful but painful DaVinci bypass of ?widow-maker? lesion but all other coronaries were 100% patent. Gets no exercise. Sarcopenia to some extent. Non-obese (never was).  Age 84 had descending colon cancer, resected successfully and clear at 5 years without chemo.   First Moderna vaccine on 2/6/2021 (lot 030120A). Flu-like symptoms next 24-48 hours, better on tylenol.  Second Moderna vaccine on 3/6/2021 (lot 048821A). Flu-like symptoms next 24 hours, better on tylenol.  2 weeks later (~3/20/2021) had an episode of legs feeling funny or weak when she stood up.  Didn?t tell anyone, but it passed by the next day.  3/6/21 to 11/16/21: saw primary care doctor for checkup (07/14/2021). BP was 120/80 as it had been this whole time even at other doctor offices (saw ENT once and oncologist another time). No illnesses.  Third Modern vaccine on 11/16/2021 (lot 013F21A?lot # may have been transcribed to her vaccine card wrong?what?s the ?F? doing there?).  3 days later (11/19/2021) had episode of feeling unusual and with legs feeling weak progressing to arms. Here?s how it progressed. That day she went to put something in the gas oven (gas leak was ruled out the next day). But she felt like her legs were weak and she felt a bit light-headed so thought it wasn?t safe to bake. She turned off the oven. She carefully made her way about 10? to the dining room table, using her arms (and some legs) as support.  She then called 911. They told her to unlock her door (apartment 1200 sq-ft) that was about 20? away. She did, and as she moved from furniture to furniture piece, the weakness worsened and moved up to the arms also; and she felt more light-headed (?out of it?).  She unlocked the door and immediately sat in the rocking chair about 2 ? from the door. The paramedics arrived and found her conscious and alert but looking a little out of it. She was taken by ambulance to the hospital around the corner. In the ER, her BP was 280/120. They reflexively put her on IVFs (NS) and gave her I.V. hydralazine, which brough the BP down to about 190/100 or so, and she felt better. Seeing repeat BPs in the 190-210 range, they decided to keep her for overnight observation. They quadrupuled her dose of enalapril to 5.0 mg po BID (am and hs) in the hospital.  AFter the morning dose, her BP came down to about 190/90; at night it was about 185/80. She ended up staying, partly at my suggestion, for another 2 nights (3 days total stay).  The night and next day of admission, COVID was (-); Stroke and spinal impingement at the vertebral fracture site were ruled out, as were cardiopulmonary problems (ECG, CXR normal). And she could walk and had not felt light-headed since unlocking the apartment door.  And she wanted to go home the entire time (real pain in the neck).  In the hospital, PT & OT assessed her ability to walk, and she did great.  At d/c, her BP was 180/60, which they felt was OK, but it had been as low as 160/80 the preceding 24 hours (once).    She followed up with her PMD 8 days later (couldn?t get appt) and BP was 180/70, and noted this was indeed very high for her. So PMD continued enalapril at 5 mg po BID.   The episode never recurred nor has she felt light-headed.  My theory is that the spike protein this vaccine forces out bodies to produce is saturating the ACE (and probably other anti-Htn receptors).   So after the 3 doses of vaccine, each producing spike protein from the mRNA transcription (turns the body into a vaccine manufacturing facility, essentially), the spike protein progressively bound up more and more ACE and other anti-htn receptors.  On dose #2, It took 2 weeks of spike protein production to probably cause pretty high BP (never measured, but likely not as high as the 3rd dose), and that?s why she had a similar but lesser reaction 2 weeks after the 2nd dose.  Then after the 3rd dose, her ACE receptors were already pretty saturated, and it didn?t take much more spike protein production to bind up the ones that were left.  That?s likely why, on the 3rd dose, she suffered nearly malignant hypertension that made her feel light-headed and experience caudal to rostral weakness. Once the BP was lowered in the ER, she felt she could walk again, and through the hospital stay. And the doctor on the unit said that indeed, very high BP could cause exactly the reaction she had.  She remains on the 5 mg po BID enalapril dose and with BPs around 150-170/60-80.