Prednisone and other corticosteroids suppress immunity much life AIDS or chemotherapy.    In this immunocompromised state the patient is susceptible to recurrence of the chicken pox virus (Varicella/Zoster virus) as Shingles (Herpes Zoster) with dreaded Postherpetic Neuralgia (nerve pain) which can be life long subsequently.   Other opportunistic infections are possible as well such as tuberculosis, influenza and pneumonia by uncommon bacteria and even cancer may advance.  

The lure of corticosteroids like prednisone and the Medrol dose pack is the illusion of feeling well as suppression of the body's defenses and immunity is accompanied by a decrease of unpleasant symptoms like fever, aches and cough.  The symptom free facade unfortunately lets invading infectious agents invade the body without resistance and allows once contained microbes to run free and multiply again.    Unfortunately, physicians have been prescribing prednisone and other corticosteroids frequently for the common cold and viral infections despite our medical school training warning of the inherent dangers.  

So when your doctor offers you a immune suppressing Rx like prednisone especially for a common respiratory virus, just say no and seek help elsewhere.   

Article:
Infection Risk and Safety of Corticosteroid Use