Group B streptococcal conjugate vaccine: a timely concept for which the time has come.

Invasive disease due to group B Streptococcus (GBS) has been recognized as a threat to the health of pregnant women and their infants for almost half a century. Development of GBS vaccine candidates has progressed at an exemplary pace given lack of sponsorship by manufacturers. A trivalent or pentavalent vaccine will be required, and decisions must be made as to the criteria by which efficacy will be determined and the population in whom efficacy will be assessed. Concerns regarding durability of conjugate vaccine-derived immunity, pregnant women as a possible target group and regulatory issues required for licensing must be resolved if the prospect of impacting GBS disease burden through immunization is to become a reality.