A 6-year-old boy is brought to the clinic by his mother for a routine health check. His father was recently diagnosed with smear-positive pulmonary TB and is starting treatment. The child is asymptomatic, with normal growth and development. Physical examination is unremarkable. Mantoux test (5 TU) shows 12 mm induration at 48 hours. Chest X-ray is completely normal. What is the most appropriate next step in management?