cyclofosfamide vincristine prednyson

What are the side effects? Is this chemotherapy a severe one?

This is fairly conventional therapy (unless the patient is recieving a very high dose of medication). Cyclophosphamide is an alkylating agent, with particular activity against lymphocytes. Even if it doesn't eliminate the malignant clone -- it may suppress the immune system which is causing the red cell aplasia. The prednisone is a steroid, chosen for lympholytic and immunosuppressive action. Vincristine is another chemotherapeutic agent with activity against lymphomas. I don't have enough details to comment on it's role in your husband's management.