Almost never get sick but I imagine this is what it must feel like to ride after being sick. Don’t know if there’s any research on the topic but my personal experience is that the day or two after getting the second Covid vaccine shot are definitely not riding or rest days. Plan for it in your training, Not sure how but jumping back into the plan didn’t work for me.
My experience: Was really psyched when I got the chance to get my 1st Covid vaccine dose in mid-March. Did a 65 mile group ride the next day. Nearly as psyched to see my second dose scheduled for the Friday before the “regeneration week” in my climbing plan. Did my climbing intervals the morning of the second dose, got the shot, felt good, went to dinner with my bride.
Woke up Saturday with chills and low energy. Sunday just low energy. Took those two days off as if they were the first two days of the regen week. Woke up Monday feeling back to normal and went out to do the FRC/Supra Threshold 4x9 (105% of threshold) per the regen week plan. Felt like absolute cr*p. Died after about 7:30 of the first repeat and 4 min of the second and rode home in barely a Zone 2 mode.
No reason or excuse not to get the vaccine. It actually feels quite liberating. Just recognize that it might affect your training schedule and ability to FtFP/turn green, etc., especially after the second shot.