Prevention of chills is related to the cause, but is often not possible. Avoiding sick people and medications that can cause chills may help prevent some cases.
Chills themselves are temporary, and cause no long-term effects. Long-term effects are entirely related to the cause. For instance, those with the flu often get better and have no long-term effects. Pneumonia may go away with treatment, but can cause death in severe cases. Autoimmune disorders can cause damage to different areas of the body, such as the kidney, joints, and lungs.
Chills are not contagious. However, if the chills are due to an infection, the infection may be contagious.