Ethical considerations for designing GBS maternal vaccine efficacy trials in low-middle income countries

Many in the scientific community agree that a randomized, placebo-controlled trial would offer the most scientifically rigorous study design for establishing the efficacy of a Group B Streptococcus (GBS) vaccine administered to pregnant women for the prevention of invasive GBS disease in young infants. There are compelling reasons to conduct such a trial in low-middle income countries (LMICs) with a high burden of disease, such as South Africa, and to adopt an add-on trial design in which participants are randomized to receive the GBS vaccine or placebo in addition to the locally available standard of care. Yet there is a longstanding debate about whether trials in LMICs should offer participants the worldwide best available standard of care. In this article, we examine both the risk-benefit profile and the potential for exploitation with an add-on trial design in the context of the locally available standard of care in South Africa. Our analysis suggests that providing the local standard of care to participants in this case may be not only more scientifically valuable but also more ethically acceptable than attempting to provide the worldwide best available standard of care in the South African setting. Moreover, the example of GBS in the South African setting can help to elucidate important ethical considerations for determining the acceptability of testing vaccine efficacy in the context of locally available rather than the worldwide best available standard of care in Phase III trials of other new maternal vaccines.