Impaired Immune System

Your immune system protects you from many illnesses. It’s your defense system. It recognizes dangers to the body and fights bacteria, viruses and other dangerous microbes to keep you healthy. An impaired immune system doesn’t protect you as well from infection.

Your immune system is made up of cells, proteins, and organs. For most people, it works well, although they still may get sick or contract an infection from time to time. This is why we get vaccinations against illnesses like tetanus, measles, and polio. Vaccines trick your body into thinking it already had the illness, making you immune to it. Other medications, like antibiotics, antivirals, antifungals, and antiparasitics help your body infections that do develop. These are all antimicrobials.

For a variety of reasons, many people are immunocompromised. Their immune system either doesn’t work well or not at all.  People with an impaired immune system are at higher risk of contracting infections, which increases their risk of developing sepsis. These infections may also be more severe.

Sepsis, which was often called blood poisoning, is the body’s life-threatening response to infection. Like strokes or heart attacks, sepsis is a medical emergency that requires rapid diagnosis and treatment.

Sepsis and septic shock can result from an infection anywhere in the body, such as pneumonia, influenza, or urinary tract infections. Worldwide, one-third of people who develop sepsis die. Many who do survive are left with life-changing effects, such as post-traumatic stress disorder (PTSD), chronic pain and fatigue, organ dysfunction (organs don’t work properly), and/or amputations.

What causes an impaired immune system?

There are several reasons for immunosuppression. Here are some of the more common ones:

Cancer treatment

Some diseases, like cancer, often need chemotherapy for treatment. While chemotherapy can be quite effective in fighting the cancer cells, it can also destroy some of the body’s healthy cells, including those that help fight infection. People undergoing chemotherapy must avoid exposure to anything that could cause illness.

Some people with cancer and other serious illnesses require a bone marrow or stem cell transplant. This also makes it hard for your body to fight infection. To prepare people for such a transplant, they must undergo chemotherapy and sometimes radiation therapy. This will destroy cancer cells and depress the immune system, so the body doesn’t reject the transplant.

Organ transplants

Organ transplants are occurring more often now, allowing people to live longer and to improve their quality of life. However, the organ recipient’s body can see these new organs as invaders, so the immune system will try to fight them. To keep the body from rejecting the organ, people with organ transplants must take immunosuppressant drugs, or anti-rejection drugs. These drugs also can reduce the ability to fight other infections, such as colds, the flu, and more.


Your spleen is a small organ in the upper part of your abdomen, near your stomach. It helps filter your blood and stores platelets and white blood cells, which fight infection. Certain illnesses can reduce how well your spleen works, such as sickle cell anemia. Technically, you can live without your spleen. People without spleens must be particularly careful to avoid exposure to anything that may cause an infection.

Other Medications

Some medications are very useful in helping treat illnesses, even preventing death. However, they can also have serious side effects, like making you more susceptible to developing an infection. These include medicines like corticosteroids, such as prednisone, and TNF inhibitors, which may be prescribed for autoimmune diseases like rheumatoid arthritis or psoriasis.

An impaired immune system is a risk factor for infection. Infection prevention is vital. This includes proper hand washing, up-to-date vaccinations, and treating infections as soon as possible. Good nutrition is also essential. Not consuming enough nutrients for your needs, can lower your body’s ability to fight infection. If you are immunocompromised and suspect an infection, mention your immunocompromised status to the healthcare professionals. This will help them with your care.

If you suspect sepsis, call 9-1-1 or go to a hospital and tell your medical professional, “I AM CONCERNED ABOUT SEPSIS.” 

The information here is also available as a Sepsis Information Guide, which is a downloadable format for easier printing.

You can also learn more about infection prevention among people who are immunocompromised by clicking here.

Would you like to share your story about sepsis or read about others who have had sepsis? Please visit Faces of Sepsis, where you will find hundreds of stories from survivors and tributes to those who died from sepsis.

Suggested Citation: Sepsis Alliance. Sepsis and Impaired Immune System. 2022.

Updated November 7, 2022.

Read Personal Stories of Sepsis and Impaired Immune System

Travis Bones

This is Travis’ story: Travis was a bright, energetic, adventurous 4-year-old who loved making people laugh. His million-dollar smile rarely left his face. On a Friday night, just days after his 4th birthday, he spiked a high fever. Initially, a nurse friend thought it was the flu and advised children’s fever-reducing medicine. His fever dropped, but overnight, his breathing became rapid and shallow. His pediatrician was called early Saturday morning, she too thought it was just the flu, but suggested Urgent Care could test him for strep throat. Urgent Care tested him for strep and type 1 diabetes. Both tests ... Read Full Story

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Pat Termini


A couple of hours before my wife Pat passed away in the ICU at her hospital, I said to her “Honey, if you have to go, I will respect your wishes, I want you to do what is best for you.” 2 hours later she passed away peacefully. I do know that she is in a much better place now, free of pain. Pat was allergic to opioid medications, which includes most everything except Tylenol. The pain from sepsis she endured those last 2 weeks must have been excruciating. Pat was a fighter. She fought squamous cell cancer for 11+ ... Read Full Story

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Rachel Davis

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On August 3rd, 2021, I was admitted to the hospital with a breakthrough case of Covid-19. (Sepsis and COVID-19) I was fully vaccinated six months prior. My CT scan showed ground glass opacities in my right lower lung. I was blessed that my oxygen saturation was within normal limits. I was in the hospital for three weeks. Upon my discharge on 8/23/21, I stayed with a dear friend for approximately two weeks. Because of malnutrition and Covid, I believe, I was immunocompromised. I had leukopenia, low neutrophil and absolute neutrophil counts, and I was anemic. (Sepsis and Impaired Immune System) ... Read Full Story

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Donna Swain

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Unfortunately, I am all too familiar with sepsis. I am very prone to UTIs, but it is rare that I recognize that I have one because I get no symptoms, until it’s too late! (Sepsis and Urinary Tract Infections) Without the usual symptoms of a UTI, the infection gets out of control and I quickly becomes septic. I must be very careful with this because in 2015, I had a liver transplant (unrelated to my UTIs or sepsis). (Sepsis and Organ Transplants, Sepsis and Impaired Immune System) Unfortunately, when I become septic, I get very confused, disoriented, and unable to ... Read Full Story

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Annmarie Williams

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Hi I am Annmarie. In 2010 I got a stomach bug and it’s changed my life. What ever the bug did affected my motility, then my gallbladder was removed. I ended up on IV nutrition in 2019. I have gastroparesis and likely severe sibo (small intestinal bacterial overgrowth). In 2020 January, I had sepsis, a bad pseudomonas infection. Luckily antibiotics worked. I then had another infection in April 2020 and a yeast infection after. (Sepsis and Bacterial Infections, Sepsis and Fungal Infections) Some how I fell pregnant with twins in June but didn’t know until September when I was 18 ... Read Full Story

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Impaired Immune System

Your immune system protects you from many illnesses. It’s your defense system. It recognizes dangers to the body and fights bacteria, viruses and other dangerous microorganisms, to keep you healthy. An impaired immune system doesn’t protect you as well from infection.