Q. A 4-month-old infant is brought to the clinic by her mother, who reports a persistent cough over the last two weeks. Initially, the cough was mild and associated with a runny nose, but it gradually became more severe. The coughing episodes are paroxysmal, often ending in a high-pitched "whoop" sound and sometimes leading to post-tussive vomiting. The mother states that the infant has been feeding less and appears fatigued. The infant has not yet received any immunizations. Physical examination reveals conjunctival hemorrhages and subcutaneous emphysema in the neck. Vital signs are within normal limits. Full laboratory findings show a normal CBC, but a nasopharyngeal swab tested positive for Bordetella pertussis DNA by PCR. A chest X-ray reveals hyperinflation but no consolidation. What is the next best step in the management of this patient?