Flu

Yesterday, Honey and I went to our local Walgreen's Pharmacy and got our Flu shots. Like Last Year, we doubled up - getting our Pneumonia vaccine while we were at it.
Last time around, my arm was sore the day of the shots, but back to normal by the following morning.  This time, my neck and shoulder are achy, and my arm feels like it is about to fall off.  
Maybe because we got our shots on Friday the 13th?