Hi, I understand your concerns. Flu is often associated with inflammation of respiratory tract including lungs. Prednisone is a potent anti-inflammatory med that will help reduce this inflammation and ease respiratory symptoms. Headache could be due to sinusitis that is often appearing after flu. An X-ray of the sinuses would confirm/rule it out. Prednisone alone won t help. Other pain killers would be recommended. I advise to measure your blood pressure (bp), and record the results. Headache sometimes is a sign of high bp. Hope this helps.