Background: Intrapartum antibiotic prophylaxis for neonatal group B streptococcal disease (GBS) effectively prevents disease among infants <7 days old, but there are no prevention strategies for late-onset GBS disease (onset on days 7-89 of life). We describe trends in late-onset GBS over a 16-year period to characterize disease burden and estimate vaccine preventability.
Methods: We conducted active, population-based surveillance for invasive late-onset GBS disease in 10 states from 1990 to 2005. A case was defined by GBS isolation from a normally sterile site on day 7-89 of life in a surveillance area resident. Incidence rates were calculated per 1000 resident live births.
Results: We identified 1726 cases; 26% presented with meningitis, and the case fatality ratio was 4.3%. Incidence was similar throughout the study period. Incidence among black infants was approximately 3 times that among non-black infants; the disparity persisted when data were stratified by gestational age. We estimate approximately 1300 cases of late-onset GBS occur annually in the United States. Birth at <37 weeks gestation was common among case-infants (49%) and was associated with elevated case fatality (relative risk: 3.8; 95% confidence interval: 1.1-13.2). Of 653 serotyped isolates, serotypes III (53%), IA (24%), and V (13%) predominated. During 2003-2005, 81 (36%) of the 227 cases caused by serotypes III, IA, and V were born before 34 weeks gestation.
Conclusions: The late-onset GBS disease burden remains substantial. A trivalent vaccine could be an effective prevention strategy. Because many cases were born preterm, reducing the opportunity for transplacental antibody transfer, adolescent immunization should be considered.