Human challenge trial

Subject: Science and tech

Context:

In January, London will begin the world’s first human challenge trial. Participants will be vaccinated with a candidate vaccine and then wilfully exposed to novel coronavirus (SARS-CoV-2) a month or so later. Over 38,000 people from 166 countries have already volunteered to participate in such studies.

Concept:

• Human challenge trials are trials in which participants are intentionally challenged (whether or not they have been vaccinated) with an infectious disease organism.
• This challenge organism may be close to wild-type and pathogenic, adapted and/or attenuated from wild-type with less or no pathogenicity, or genetically modified in some manner.
• Human challenge trials have been performed safely in tens of thousands of people in the last 50 years and have helped accelerate the development of vaccines against typhoid and cholera. Such a study was also conducted for Zika virus.
• The yellow fever experiments conducted in the early 1900s helped prove that mosquitoes transmit the virus causing yellow fever. The human-challenge studies have generally been used for testing less deadly diseases such as influenza, dengue, typhoid, cholera and malaria.
• In May the WHO approved human challenge trials and NIH too is developing two viral strains through Colorado State University that can be used in human challenge trials.