Your immune system keeps you healthy by fighting off germs. But sometimes, due to external factors (those not caused by genetics) people develop what’s known as a secondary immunodeficiency (SID). Just like with a primary immunodeficiency, the outcome can be life marked by seemingly never-ending infections and colds that just don’t go away. As a result, patients may face repeated rounds of antibiotics and hospitalization for treatment. SID is much more common than primary (genetic) immunodeficiencies.