Hi and thanks for the query, Persistence of these symptoms warrant a consultation with a physician. This deserves a proper clinical evaluation. Flu infections are generally viral and the outcome is usually simple and favorable. At times, it might persist, and if it does, more stringent measures. This is because if the phlegm persists, it might predispose to bacterial infections. I strongly suggest you consult your physician for a proper evaluation. Other more effective drugs, generally mycolytics could be helpful. A more aggressive evaluation and management could prevent any subsequent complications and improve the quality of life of the child. I strongly suggest you consult your family physician or pediatrician. Thanks and best regards, Luchuo, MD.