The current state of immunization against Gram-negative bacteria in children: a review of the literature.

Purpose of review Gram-negative bacteria (GNB) are a major cause of infection worldwide and multidrug resistance in infants and children. The major pathogens include Klebsiella pneumoniae, Escherichia coli, Enterobacter spp., Pseudomonas aeruginosa and Acinetobacter baumannii. With new antibiotic options limited, immunization is likely to play a critical role in prevention. This review discusses their epidemiology, the current state of vaccine research and potential immunization strategies to protect children. A comprehensive review of the literature, conference abstracts along with web searches was performed to identify current and investigational vaccines against the major GNB in children. Recent findings Phase I--III vaccine trials have been undertaken for the major Gram-negative bacteria but not in infants or children. E. coli is a common infection in immune-competent children, including neonatal sepsis. Several vaccines are in late-phase clinical trials, with some already licensed for recurrent urinary tract infections in women. Klebsiella spp. causes community-acquired and hospital-acquired infections, including sepsis in neonates and immunocompromised children although no vaccine trials have extended beyond early phase 2 trials. P. aeruginosa is a common pathogen in patients with cystic fibrosis. Phase 1--3 vaccine and monoclonal antibody trials are in progress, although candidates provide limited coverage against pathogenic strains. Enterobacter spp. and A. baumannii largely cause hospital-acquired infections with experimental vaccines limited to phase 1 research. The current immunization pipelines for the most prevalent GNB are years away from licensure. Similar to incentives for new antibiotics, global efforts are warranted to expedite the development of effective vaccines.