A Review of Current Knowledge on the Development of a Group B Streptococcus Vaccine for Pregnant Women and the Protection of Neonates: Advances in Diagnosis and Treatment

Streptococcal infection remains the leading cause of neonatal sepsis and death. Systematic use of antibiotic prophylaxis and advanced neonatal care guidelines aiming in the restriction and elimination of adverse effects on neonatal Group B Streptococcus disease neither eliminated it nor restricted it. Maternal immunisation with a Group B Streptococcus vaccine is considered the best strategy for the prevention of both early and late-onset invasive Group B Streptococcus disease. However, such an effective vaccine has yet to be fully licensed, although various attempts through the years have been made. At present, a hexavalent Ia, Ib, II, III, IV and V glyco-conjugate vaccine has completed Phase I clinical trials, showed promising results among healthy adults and was allowed to undergo Phase II trials. The early observations are promising allowing larger studies for determining the factors of optimal efficacy, such as timing of administration. The specific timing of administering a Group B Streptococcus vaccine during pregnancy has yet to be determined, although evidence show that for maximum levels of anti Group B Streptococcus antibodies to be transferred to the fetus, the best time of administration is during the second half of pregnancy or early on the third trimester. Furthermore, it remains uncertain if the vaccine should be recommended to all pregnant women, only those at higher risk or those testing positive, nor are specified the benefits of a second dose. In addition, a large Phase III clinical trial is required in order to evaluate possible adverse effects, including neuro-developmental assessments of the infants born to vaccinated mothers prior to licensing any vaccine candidate.