Human challenge models for vaccine development-strengths, limitations, and expansion into endemic settings: a HIC-Vac meeting report.

The HIC-Vac network is a unique association of researchers focussed on the development and use of human infection challenge (HIC, otherwise known as controlled human infection models or CHIM) studies for vaccine and therapeutic development, particularly for pathogens of high global impact. The fifth annual meeting of the HIC-Vac network was held on 1-3 November 2023. The theme of the meeting was capacity-building in endemic settings particularly in low- and middle-income countries (LMIC), where pathogens cause the greatest morbidity and mortality. In this report we highlight the strengths and limitations of HIC and expansion of such studies into endemic settings, noting that immune responses and vaccine efficacy differ across diverse settings and populations. The consensus was that HIC studies must not be restricted to high income settings if they are to be relevant to LMIC populations. This report summarizes the work presented at the HIC-Vac annual meeting, highlighting current and future challenge models, challenge agent manufacture, public engagement, ethics, and industry perspectives.