Booster yesterday. Pfizer as were the first two.
With the first two I had no effects other than a transient aching arm muscle.
With this one within a couple of hours my arm was aching, and 12 hours lated felt heavy and stiff. But worse, at about 10 hours I had really bad 'flu like' symptoms - aching, feeling hot, lethargic etc.
I visited the 'pharmacy-in-the-spare-bedroom' which helped a bit, then went to bed and went straight to sleep (which isn't normal).
This morning I've got a sore arm and a bit of a headache, but the aches have gone.
This doesn't seem to fit with the normally reported course of booster side effects, but I'm not stressing over it. I'm guessing it was my immune system working weekend overtime.