Hi, I took my dog for her annual booster injection yesterday. She is 8 years old and a cross between a dacshund and chiauaua and normally such a happy dog and full of energy. Today though she hasn't moved from her bed and just seems really tired. I don't recall her being like this before after her booster. Does anyone else know if this is a common reaction? Also, I have read that having an annual booster is actually unnecessary. Is there any truth in this? Thank you.