5 Infections in Immunocompromised Patients

How immune impairment changes risk

Infection risk depends on which immune defenses are impaired and how strongly and how long they are suppressed. It is also affected by implanted devices, damaged skin or mucosal barriers, and relevant exposures.

Neutrophil defects raise the risk of bacterial and fungal infections, while impaired T-cell function increases susceptibility to certain viral, fungal, and protozoal infections. These patterns help guide assessment, but they do not predict which infection an individual will develop; the specific immune defect and clinical history matter.

Opportunistic infections and transplantation

An opportunistic infection occurs more often or causes more severe disease when immune defenses are weakened. Examples include Pneumocystis jirovecii pneumonia in some people with advanced HIV, invasive aspergillosis during prolonged severe neutropenia, and cytomegalovirus disease after transplantation. These examples are not predictions for every patient; individual immune status and clinical history guide which infections are more likely.

Infection risk after transplantation reflects a balance between preventing rejection and restoring immune defenses. Risk varies with the type of transplant, immunosuppressive regimen, complications such as graft-versus-host disease, and time since transplantation. After hematopoietic cell transplantation, early risks can include infections associated with neutropenia and damaged mucosal barriers; later risks vary with immune recovery and ongoing immunosuppression.

Prevention and vaccination

Prevention should be tailored to the patient’s condition and treatment. Practical measures can reduce exposure and protect routes through which infection may enter.

• Reduce exposure: Practice hand hygiene, avoid close contact with people who are ill, and use additional respiratory precautions when appropriate. Follow food-safety practices, including avoiding higher-risk foods such as unpasteurized products and undercooked meat or eggs.

• Protect skin and devices: Care for wounds and follow instructions for central lines and other medical devices. Promptly report redness, pain, drainage, or problems with a device.

• Consider antimicrobial prophylaxis: Preventive medicines may be recommended for particular conditions, treatments, or transplant phases. They are not appropriate for everyone; the care team determines the need and duration.

Vaccination planning should include reviewing vaccine history before immunosuppressive treatment when feasible. Non-live vaccines are generally safe, although the immune response may be reduced during some treatments. Live vaccines are generally avoided in people with significant immunocompromise because the vaccine organism can cause disease. Exceptions and timing depend on the immune condition and treatment, so coordinate decisions with the treating team.

Keeping household members up to date on recommended vaccines can reduce exposure to vaccine-preventable infections. Some live vaccines require special consideration around severely immunosuppressed patients. Transplant recipients need an individualized prevention and vaccination plan coordinated with their transplant team.

Recognizing and evaluating infection

Infection may progress quickly or appear without typical signs in an immunocompromised patient. Fever may be absent or muted, and inflammation may be less obvious. New confusion, weakness, shortness of breath, cough, diarrhea, pain, skin changes, or a sudden decline in function can be important clues even without fever.

Evaluation considers current symptoms and vital signs, the immune condition, recent and current medicines, transplant history, devices, prior infections, prophylaxis, vaccination history, and relevant exposures. The clinician examines for possible sources and selects tests according to the presentation; examples include blood counts, cultures, imaging, and targeted pathogen tests. A negative initial test does not always exclude infection, so further evaluation may be needed if symptoms persist or worsen.

Fever with severe neutropenia

Fever with known or suspected severe neutropenia is an emergency. The patient needs prompt clinical assessment and empiric treatment; evaluation should not delay urgent treatment. IDSA guidance recommends giving initial empiric antibiotics within one hour of triage for febrile neutropenia.

The priority is urgent clinical evaluation and prompt empiric treatment, rather than waiting for all test results. This urgency applies even when other typical signs of infection are muted.