Think of it this way
Jesse Cloud
When you get the second dose, the body has been primed to recognize it as an invading object. Your immune system already knows how to make the antibodies and sets to work.
The immune system needs a terrific amount of your body's resources: water, energy, amino acids, etc. and takes those away from normal body functioning. That is why so many feel lethargic.
So stay hydrated after the shot, get some rest, take some nutrition, and some Tylenol or such to ease the pain.
And do get that second dose!! If any doubt call your doctor.
And one little rant. OK Pfizer and Moderna tested thousands of people and only 5% of them got Covid -- that's great, but NOT PERFECT. If you often go to bars, crowded restaurants, and other places where people are not wearing masks the odds are that you will get enough exposures to be at risk.

