The human immune system is the body’s natural defense against infections and diseases. It consists of antibodies, white blood cells, the complement system, lymphatic system, spleen, the thymus, and bone marrow. Although these are considered to be the central immune organs, most of the immune cells are found in the peripheral immune system.The peripheral immune system has got lymph nodes, spleen, liver, mucosa of digestive, respiratory systems, skin, and more. Together, they keep us healthy. But, what happens if our immune system fails?Types of ImmunityThere are three types of immunity — innate, adaptive, and passive. Innate immunity, for example, skin, serves as a natural barrier to stop viruses, bacteria, and parasites from invading the body. It can automatically recognize what’s foreign to the body and block the bad stuff.Adaptive immunity is a type of immunity that we develop as we grow up when we are exposed to pathogens or get a vaccine shot. It can destroy microbes and parasites through different protective barriers. It is highly specific to the particular pathogen that we came in contact with. Once we come in touch with a particular disease, we get immunized against catching it the next time we’re exposed to its pathogens.[caption id="attachment_38421" align="alignright" width="300"] Vaccine administration. Image via U.S. Air Force photo/Senior Airman Areca T. Wilson via Science360. U.S. government image.[/caption]We get passive immunity by receiving antibodies from another source  — from our mother when we are born or from an injection or infusion. It’s short-lasting compared to adaptive immunity, lasting from a few weeks to a few months. It can be artificially given to someone who doesn’t respond to active immunization by vaccination.Primary and Secondary Immunodeficiency DisordersWhen the immune system is weakened for an extended period by severe disease or drug use, a person can develop immunodeficiency disorder. They can also be inherited. When that happens, the immune system can’t defend the body against microbes like it usually does.Primary immunodeficiency disorders occur when the immune system doesn’t function properly, sometimes due to genetic causes. These include X-linked agammaglobulinemia, common variable immunodeficiency, and severe combined immunodeficiency.Secondary immunodeficiency disorders are caused by an outside source, such as severe burns, chemotherapy, radiation, diabetes, or malnutrition. They are AIDS, leukemia, viral hepatitis, and multiple myeloma.Symptoms of ImmunodeficiencySymptoms of primary immunodeficiency are frequent infections that are harder to treat, such as inflammation and infection of internal organs, blood disorders, digestive problems, delayed growth, or autoimmune diseases. Symptoms of secondary immunodeficiency are fatigue, stress, pain, anxiousness, and depression.Are Vaccines Safe If You Are Immunodeficient?Vaccines can generally prevent infections and are safe for most people who don’t have dangerous comorbidities. Immunodeficient people can benefit greatly from getting vaccinated to reduce the risk of diseases. However, the way a vaccine works is by injecting an antigen into the body to create an immune response.Sometimes, immunocompromised people may need to receive multiple vaccines to develop protection. Nevertheless, live vaccines should be avoided for those who are severely compromised. Influenza, pneumococcal, and other inactivated vaccines are considered safe for immunocompromised people. Those less severely immunocompromised may receive live vaccines such as MMR, MMRV, rotavirus, zoster, and yellow fever. BCG and oral typhoid shouldn’t be used in any case.It’s also essential that the whole household gets vaccinated, to increase protection of their immunocompromised family members.ConclusionFrom the moment we are born, we start receiving antibodies from our mother in a natural way to help protect us against diseases. As we grow and get exposed to pathogens, we also acquire the ability to remain healthy ourselves. With modern medicine, a plethora of vaccines is available for various ailments as well. This all plays a part in building our immune system. An uncompromised immune system functions like clockwork and will protect the body against viruses and bacteria. However, immunodeficiency disorders can disrupt the immunity in people. We can help the immune system stay active with vaccination, but doctors must be cautious when choosing a vaccine for immunodeficient people.