I did have some warning that this might happen, but one cannot prepare for these things I guess, not really.
My mother had nearly zero reaction to both the first and second shots of the Pfizer vaccine. Some shoulder muscle aches after the first one, some a bit longer muscle aches after the second one but nothing more. My father had almost no side effects after the first one (he has not got the second one yet) and I got only shoulder ache after the first shot, albeit big enough to not being able to sleep for one night and work for one day properly. But it subsided after 24 hours and I was completely OK the day after.
Not after the second shot though. I got it on Wednesday afternoon and at first, it progressed the same as the first shot – my shoulder began to ache, I could not lift my arm and I could not sleep properly because I am used to falling asleep on my left side. However, this time it did not stop there. at 4 a.m. I got serious shivers so I have measured my temperature and I was 1°C above my personal normal. That not only did not go away until noon, it also got in fact worse – at noon I had 1,5°C above my personal normal. I no longer had shivers, I was drenched in sweat instead. And not only my right shoulder muscle was aching, but multiple joints also did, continuously. Especially my fingers and spine. I had to take Paracetamol to fight the temperature. Whether it helped or not I cannot tell. It stopped rising, but it also did not go down and I had to take another at 20:00 after dinner. And I still had to change my beadsheets and pajamas during the night because I was sweating profusely.
Today morning I no longer had a fever and the aches have mostly receded, but I was still weak, I mostly slept until noon and I remained in bed until now, which is about 16:00. I am now mostly pain-free, but I still feel tired like after a day of work and not a day of layaboutism.
The last time I felt this crappy was the previous year when the flu knocked me out. Only that time it took two weeks, not two days. If a vaccine does this to me, I do not ever want to know what the actual coronavirus would have done, I might not live to tell the tale. Yay for vaccines, even when they give you the taste of the real deal.