Interesting to note the 24 hour effect of the vaccine, my mother in law was in Hospital for 5 weeks for major heart surgery, late Jan and all of Feb. See said that when they vaccinated the staff in early February, the younger ones felt dreadful for 24 hours (many going home) and the older ones less so.... Curious, I would suppose it's a simple immune response, that's clearly stonger in a younger immune system?
Certainly my parents, both in their 80's reported no ill effects, other than a slightly sore arm for the following day.