To reduce the global burden of the COVID-19 pandemic, there is an urgent need to develop a safe vaccine. Vaccine development usually takes many years as it goes through several different phases. To hasten COVID-19 vaccine development, it has been suggested that the final stage could be replaced with a human challenge trial (HCT). Volunteers would be intentionally infected with SARS-CoV-2 to see how the vaccine candidate works. To intentionally infect a healthy human being with a potentially deadly virus is contrary to the highest ethical standards in medical research. This article highlights the benefits and risks of COVID-19 HCTs and summarises what research ethics committees (RECs) need to consider during the ethical assessment of such trials including risk reduction, strict containment measures, specific informed consent measures and avoiding high monetary inducements.