Coronavirus vaccine race: Are human challenge trials ethical? Experts are divided

Human challenge study in the development of a vaccine refers to
exposing healthy volunteers to a pathogen and then monitoring them in
a clinical setting to see how they react to the virus. The challenge
trial becomes controversial in settings where there is no proven
treatment or cure for an infectious disease. Covid-19 is one such
disease.

https://economictimes.indiatimes.com/industry/healthcare/biotech/pharmaceuticals/coronavirus-vaccine-race-are-human-challenge-trials-ethical-experts-are-divided/articleshow/77295284.cms