Ever since comjng down with the flu and losing a week (Jan '09?), I haven't missed a vaccine. Never had one before then. It is NOT mistakable for a cold--high fever, sweats, chills, runny nose, your whole freakin' body hurts. Three days in bed, shoulda been four but I was stupid and worked two half days, then laid around under a blanket all weekend, resting.
Woke up sick on Sunday morning; by Monday evening, I was afraid I was gonna die; by Tuesday evening, I was afraid I wasn't gonna die. Worked Thursday morning, shouldn't have. Went back Friday morning because I'm stubborn. By next Monday, I was back up to an honest 75%.
Don't want to go there again. Got my vaccine two weeks ago.
Does your arm get sore? Use it! Do a half dozen pushups, even doorway pushups. Use the muscle some, you'll like how the pain just goes away in a little while. Works for tetanus shots, too. Or sit there all still, and hurt--it's your arm and your choice.