Hello and thanks for writing in at HCM
The reasons for consistent fever
1. Vomits after taking the medicine. With vomit medication comes out or in other way you misses the dose. That cause the infection in the lungs to grow and at last results in fever.
2. The antibiotic you are taking are resistant to the bacteria causing pneumonia
. Hence the antibiotic (although taken all the doses) doesn't effect on it and the infection increases.
Now my advise to you is to consult your doctor again and revise the doses and ask the doctor for I.V. administration of the antibiotic that will help in quick healing.
Additionally if your nephew has associated symptoms (you have not explained it in your mail) like breathlessness, high grade fever not reducing with antipyretics than go and admit him in the hospital.
Hope you have got answer to all your queries