Human challenge trials in vaccine development: Strasbourg, September 29 – October 1, 2014

• For some important vaccines human challenge trials may be the best route to advance development.
• HCTs have been performed successfully, safely and ethically, to support vaccine development.
• With regulatory acceptance HCT may accelerate vaccine development for unmet medical needs.
• An international expert workshop was convened to discuss current and future prospects for HCTs.
• We propose twenty recommendations for consideration to develop international guidelines.

An international workshop to discuss the role of Human Challenge Trials (HCT) in vaccine development was held in Strasbourg, France from 29 September to 1 October 2015. In addition to scientific presentations, several panel discussions focused on key questions and proposed recommendations, including the acknowledgement that HCT have proven to be useful tools to explore vaccine targets, identify immune correlates of protection, and evaluate clinical efficacy, and when appropriate they should be continued and encouraged. In some cases, a HCT may be the only feasible way to move forward with development of an investigational product. HCT must be strongly scientifically justified, because the need for a given investigational objective must be always balanced against the risks a HCT may pose, understanding that an infectious organism will be given to the study participants. It should be noted that numerous HCT have been successfully performed, safely and ethically, to the benefit of vaccine development and public health. This workshop report highlights the scientific presentations, discussions by the panelists and attendees, and twenty recommendations that emerged as considerations for future development of international guidance on the role of HCT in vaccine development and licensure.