Human infection challenge in the pandemic era and beyond, HIC-Vac annual meeting report, 2022

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.

Generating prophylactic immunity against arboviruses in vertebrates and invertebrates

The World Health Organization recently declared a global initiative to control arboviral diseases. These are mainly caused by pathogenic flaviviruses (such as dengue, yellow fever and Zika viruses) and alphaviruses (such as chikungunya and Venezuelan equine encephalitis viruses). Vaccines represent key interventions for these viruses, with licensed human and/or veterinary vaccines being available for several members of both genera. However, a hurdle for the licensing of new vaccines is the epidemic nature of many arboviruses, which presents logistical challenges for phase III efficacy trials. Furthermore, our ability to predict or measure the post-vaccination immune responses that are sufficient for subclinical outcomes post-infection is limited. Given that arboviruses are also subject to control by the immune system of their insect vectors, several approaches are now emerging that aim to augment antiviral immunity in mosquitoes, including Wolbachia infection, transgenic mosquitoes, insect-specific viruses and paratransgenesis. In this Review, we discuss recent advances, current challenges and future prospects in exploiting both vertebrate and invertebrate immune systems for the control of flaviviral and alphaviral diseases.