M57, name some immune boosters to control this flu/cold not coming to control even after 12 days and antibiotic.thanks?

Not flu: Flu shouldn't last 12 days, and it shouldn't be treated with antibiotics, as it is a virus and antibiotics has no effects on it, if you have been ill that long i advise you to see your doctor for a full eval.

Rest: There is nothing else that has survived rigorous investigation other than sleep. Jury is still out on vitamin c. Be health by; not smoking; eating diet rich in fiber, fruits and vegetables, exercising regularly, maintain a healthy weight, control blood pressure, drink alcohol in moderation if at all, avoid getting infections by washing hands, fruits and veggies and cooking meats thoroughly.