MMR vaccination, high WBC count

Patient: Hi,My son is 14 months old, 12 days earlier he was having cold, cough and fever….we went to doctor and doctor gave him Claritin…and on the same day doctor gave him MMR vaccine also…. 5 days after vaccination he got very high fever (103-104) …and it last for nearly 5 days… on 4th day doctor advised us to admit our son and kept him on IVF as his food and liquid intake was going down gradually…….yesterday we got his blood test reports and his WBC count was very high near to 20,000. doctor gave him some antibiotics through IVF………..and today he is feeling better…….no fever…..started eating little bit.What may be the cause for high WBC count in my son?

Symptoms: high fever, cough, cold, sore throat, high wbc count, low intake of food and liquid, bloating, gas pain