I had the second Moderna shot that afternoon, scheduled for 4:15pm but it was about 4:30pm when I got it.  I moved around as instructed by my doc, and after 15 minutes went back to my car.  I noticed after another several minutes that my pulse was still elevated so opted to go back in and talk to a health care professional.  Pulse was 120.  Paramedic wanted me to lie down in waiting area but I didn't want to be in such a potentially  germy environment, and the guy next to me who had fainted earlier was just getting up himself.  She walked me back to my car, where I agreed to wait, listen to a stress relief hypnosis audio and see if my pulse rate would calm down.  She came back out w/ a BP cuff and said my blood pressure was 210 over 130 (or some number over 100; I don't recall which) and she said I needed to get in an ambulance right away and go to the hospital.  I said I would make my own decisions about my body and I wanted to try a couple of other things first, promised not to leave, contacted my doctor, naturopath.  (Note: I did not have any other worrisome symptoms -- blurred vision, dizziness, etc.  My head was a little buzzy, but whether out of fear or in reaction to the shot I didn't know.  I was a little flushed).  He asked me a bunch of questions, said my body hadn't had time to mount an immune response to the vaccine and that I had likely had a histamine reaction to a preservative in the vaccine (or similar), which a couple of his other patients had experienced.  He asked if I'd been drinking fluids (yes, plenty), had eaten recently (no, so he suggested I have some food; I had some nuts, a little cheese and some Cheez-Its so had that), asked if I had an antihistamine around -- I did, but I don't do well with Benadryl and didn't have Claritin, but after looking through my bag found some Allervive, an herbal product he compounds.  He said, "That's perfect."  I took two of the three capsules and hung up.  Staff were checking up on me in my car every ten minutes or so, by the way, very kind and professional as I had been quite upset at the whole "get in an ambulance" scenario.  He thought some of my reaction was probably also stress-related, and I noticed before the shot that I was teary, not from anxiety but the kind you get when you feel relief after a long ordeal.  I didn't feel anxiety, really, until the first blood pressure measurement.  He also let me know that if the bottom number didn't drop below 100 they couldn't let me go.  After eating, drinking some more water and taking the Allervive my BP was down to 138 over 75 in just a few minutes.  I agreed to stick around and make sure it stuck.  We re-tested again about 15 minutes later, perhaps longer, and it was the same.  I had been a little flushed but that had gone away too.  I left and went for a light walk and eventually drove home without incident.  I had symptoms after the shot that could have been related to my body fighting off the allergic reaction or to the vaccine itself, but they were pretty mild (fatigue later that night; occasional heart rate elevation sometimes after eating or with very mild exertion -- not unusual for me if I'm "fighting off" something; sore, itchy, red blotch sized between a quarter and a half dollar at vaccination site -- it is still a little tender today and appears a bit bruised; a bit sinus headache-y for three days, especially when I bent down to tie my shoes or something like that - also not that unusual as I often seem to "cleanse" through my sinuses when I have a bug or am fighting something off).    In hindsight, I think the symptoms I had after the first shot, which lasted about 9 hours, may have been fighting off the allergic reaction and not a reaction to the virus vaccine itself.