Infection is a prominent problem among most patients in the pediatric intensive care unit (PICU) and plays a role in the care of virtually all whose stays are measured in weeks rather than days.
Infectious disease is very much a part of the PICU landscape, due to the nature of infants and children as well as to the nature (and technology) of the modern critical care environment. Young patients are disadvantaged by the immaturity of their immune systems, their lack of prior exposure to antigens, and their relatively porous physical barriers to microbial invaders. T-cell function matures over the early weeks of life, during which young infants remain highly vulnerable to intracellular organisms, such as tubercle bacillus. B-cell function develops a bit later, so by age 4 to 6 months the antigens in the primary series of vaccines induce brisk antibody response, immunologic memory, and clinical protection. Yet the ability to mount a protective B-cell response to other antigenic stimuli (capsular polysaccharide antigens, for example) must await maturation of certain splenic B-cells,
perhaps not until age 2 years.
Widome MD. Infectious Diseases in the Pediatric Intensive Care Unit. JAMA. 2008;299(9):1072-1073. doi:10.1001/jama.299.9.1072