Following an injection of Interferon, you can expect to feel like you have the flu, influenza not just the common cold. Symptoms can include fever, chills, headache, muscle aches and pains and malaise. The symptoms vary from mild to severe and occur in up to half of all patients. The symptoms tend to diminish with repeated injections and may be managed with analgesics and antihistamines. Your doctor will advise you on what you can take to manage the symptoms.