DEVELOPMENTAL IMMUNOLOGY OF THE NEWBORN

Abstract

The increased susceptibility of newborns, especially those born prematurely to serious infections has been well documented.@, 48* 62 Despite advances in antimicrobial therapy and neonatal intensive care, neonatal infections continue to be an important determinant of childhood morbidityand mortality in both developed and Third World c~untries.~ The incidence of neonatal sepsis has remained unchanged and ranges from 1 to 10 per 1000 live births with an even higher incidence of 21 per 1000 live births among the developing countries where access to sophisticated ”modem” technology is limited.=, 40, 141 Concurrent meningitis, associated with a high risk of neurologic morbidity, occurs in about one fourth of cases.@ In the preantibiotic era, neonatal sepsis was almost always fatal. Mortality has decreased sigruficantly after the introduction of antimicrobial agents and technologic advances in neonatal management. In the past 15 years, the case-fatality rate for noninfectious neonatal illnesses has continued to decline, whereas that for infectious diseases has reached a plateau of approximately 15% for late-onset sepsis (sepsis that occurs between 4 and 30 days of life), and 15% to 50% for early-onset sepsis (sepsis that occurs in the first 4 days of life).a The impact of neonatal infections as a significant cause of neonatal death globally is more evident in developing countries, as recently reviewed by St~ll.~~~ Neonatal infections are responsible for between 1.5 and 2 million neonatal deaths per year, or between 4000 and 5000 deaths per day in the less developed countries of the w0r1d.l~~ The incidence of neonatal sepsis is even higher and inversely proportional to the gestational age and birth weight. In Israeli, Finnish, and American studies, very low birth weight infants (VLBW; weighing 4500