What Causes Itchy Patches Behind Knee After Having Prevnar-13?

Hi I had the Prevnar 13 pneumonia shot on 1/27. In a few days I began getting some patches of irritation in a few places: by my knee on right leg and behind my left knee. Each day a few more places appear. There is severe itching. I took a Benedryl last night and today the rash is on thighs, shins and a few places on arms and a couple on my back. Is it possibly connected to the shot?