challenge trial

 This is the common short version of human challenge trial which could be the shortcut to testing a possible vaccine for SARS-COV-2.  The idea is that a small group of volunteers are given the vaccine which is then challenged by the introduction of the virus. If the group do not get COVID-19 then there is a good chance that the vaccine has worked. The alternative to this is vaccinating a large group of people while selecting another group as a control, waiting to see what happens in normal circumstances to both groups and finding out if the group with the vaccine does better than the control group.

 Of course if the vaccine used in the challenge trial does not work, then the volunteers could get the disease.  They need to be young and healthy and to be given the highest level of treatment if they do become ill.  The ethics of the challenge trial are difficult but it is clear that the volunteers need to be given the best possible chance to survive, and that the risk to them is outweighed by the benefit to the huge numbers of people who would die if the world struggles on without a vaccine.