Symptoms & time course 03/31/21:  Within 2-3 min after taking the Covid-19 Pfizer shot in my left upper arm, my entire arm became nearly 80% immobilized ( I felt that I was going to lose my arm movement completely but it came back). In about 5 min time, I felt a strong stomach disturbance (something like stomach diarrhea) briefly for a few seconds, and then my heart rate increased suddenly a lot and I felt a strong gush of heat coming out of my face and upper half of the body, and then I started to feel unwell. I also felt moderate pressure in my ears and the head wasn't feeling well either. My hands and fingers were trembling a lot. The paramedics checked my vitals, I think the blood pressure was around 117/62 and  pulse was around 85. After another 5 minutes or so, I started to feel better.   For the next 2-3 hours post-vaccination, I had felt mild symptoms of headache, nausea, and sensation of cough in the throat. Few times I also felt mild sensations of chest discomfort and that I may develop some difficulty in breathing or shortness of breath, and once I also felt a mild sensation of throat moving up and down (no throat closure), and none of these symptoms had developed to that of a higher intensity such that someone else could see them happening. About 5 hours post-vaccination (i.e. around 8:30 pm) I felt that I have a reaction going on in the body which continued for an hour. About 6 hours post-vaccination (i.e. around 9:30 pm), I felt that the reaction that was occurring in the body had ended with the skin on both of my arms becoming red in color and the skin texture was looking like that of a burnt skin (I did not take a picture of the arm with skin redness). The whole-left-arm had swollen relatively more than the whole-right-arm and I also noted mild swelling in the left arm wrist and palm. Also, a large part of the muscle just above the elbow on the left arm had swollen a lot (appearing like a bump) with muscle stiffness, and this muscle bump was mildly painful if you apply pressure on to it. There were also some mildly painful nodules in the upper left arm and the arm muscles generally appeared to be hardened. The veins & some arteries also appeared more prominent in the left arm compared to the right arm. I had noted that the swelling and redness in both the arms had started to decrease after 30 min of appearing and got reduced a lot more after about 2 hours (i.e. 11:30 pm). There was also a very mild facial swelling at night and I had felt feverish for about 25 min or so.   04/01/21 Next day early morning (i.e. 6 am) I noted abdominal or stomach bloating of higher magnitude, and I wasn't feeling very well with some mild sensations of throat moving up and down and a feeling that I may develop shortness of breath but these symptoms did not develop in higher intensity and began to subside after about an hour. As the day progressed, I started to feel better and by afternoon all of the symptoms were better except that the swelling and a hive (or muscle bump) on the left arm were still present. I also had moderate soreness around the site of injection in the upper left arm.  04/02/21 Next day morning the swelling and hive (or muscle bump) in the upper left arm were getting better but had not completely gone. By the end of the day the arm swelling had mostly subsided and the large muscle bump in the upper arm had reduced in size but still present with a mild pain. The left upper arm soreness around the site of injection had reduced.  04/03/21 & 04/04/21 The hive or (muscle bump) in the upper left arm was highly reduced in size but still present with a mild pain on applying pressure.  04/05/21 I felt some minor chest discomfort and minor pain repeatedly for a few seconds during the afternoon hours while at work. These symptoms subsided by evening hours.  04/06/21 I felt a mild chest congestion with a little bit of phlem in the chest at night which then got better after an hour or so.  04/14/21 I noted a rash on the left side of the lower neck (just above the shoulder) which extended from the left-side of the neck towards the center of neck, at night (i.e. 11:45 pm). The intensity of redness had reduced in the next 30 min or so and the rash was nearly gone by the next day morning.  Final outcomes: The allergic reaction symptoms that I had developed after taking the first dose of Covid-19 vaccine from Pfizer-BioNTech had mostly resolved on their own in a week. I did not take any medications to help relieve the allergy symptoms.   Concerns and queries:  1) Would it be safe for me to take a second dose of Covid-19 vaccine from Pfizer-BioNTech?  2) Would an anti-allergy medication be helpful to take before receiving a second dose of Covid-19 vaccine from Pfizer-BioNTech?  3) Is it safe to receive a Covid-19 vaccine from a different company (e.g. Johnson & Johnson or Novavax)? I am presently partially vaccinated.