Sudden drop in body temperature after immunisation?

My baby is fine now but I'm curious...

My baby had his first needles today and developed a reaction - hives, that went away within 10 minutes. They told me to monitor him and about 4 hours later, he was screaming in extreme pain and suddenly got very cold. I got in the bath with him, warmed him up, gave him tylenol and about half an hour later he was warm and ok. I spoke with the health nurse who said to continue tylenol and keep a close watch on him. Has anyone heard of a body temperature drop from immunisation? I cannot find any information linked to anything but a fever and some pain but not a drop in body temperature. He was very cold and shivering and screaming. I'm quite worried that it is a delayed reaction. The health region is investigating but the nurse said she had not seen that before.

His cold skin could be an adverse reaction from a SPIKE in body temperature. All of his blood rushing inside to wherever and his skin getting cold and clammy. He could've been ready to throw up. It could be a number of things, but see what happens next time. Good luck and I'm sorry your little one had such a hard time with his shots.

Infections and immune response in general can cause hypothermia.

http://www.webmd.com/a-to-z-guides/body-...
A low body temperature may also be present with an infection, particularly in newborns, older adults, or people who are frail. An overwhelming infection, such as sepsis, may also cause an abnormally low body temperature.