 [ Symptoms ] how can i protect myself from pneumonia [ Disease ] fever is the body is response to inflammation or infection amoxicillin is only effective for a bacterial infection like strep it is absolutely no effect on viruses a person can contract a virus anytime even while taking an antibiotic fever does not really shock or bother medical professionals as much as it does parents but i cannot blindly tell you the significance of this brief transient fever i do not know anything about your son what you really mean by a spike so when in doubt call his medical provider    someone who knows him his particular case and someone that can offer you the patient specific advice that you really need