 Group B streptococcus, GBS, is a life-threatening disease in newborns caused by pregnant women colonized with the bacteria which can lead to sepsis, meningitis, pneumonia, or death. A GBS vaccine administered during pregnancy could potentially address this unmet medical need and provide an adjunct or alternative to IAP for prevention of invasive GBS disease in neonates. However, low disease rates make efficacy studies difficult, but licensure using serological criteria as a surrogate biomarker represents a promising approach to accelerate the availability of a GBS vaccine. This article was authored by Judith Absalon, Raphael Simon, David Radley, and others.