I will fifth that on sounds like shingles. Did he have a shingles shot in the past?
My husband and I had the Pfizer in February and neither of us had reactions on either shot. I had friends and one of my doctors that had the Moderna/Pfizer and experienced extreme sluggishness for a day. At first I worried that the shots did not work for my husband and me, but I got over it. Now I am a happy camper.
As a point of reference, my wife had the original Shingles vaccine and promptly had two cases of Shingles after it. A vaccine is NOT the cure-all some make it out to be.
She also had the Moderna Covid vaccine and had a bad 18 hours after the second shot.
