Vaccine Testing May Fail Without Human Challenge Trials

In Why Human Challenge Trials Will Be Necessary to Get a Coronavirus Vaccine I asked, “What if we develop a vaccine for COVID-19 but can’t find enough patients–healthy yet who might get sick–to run a randomized clinical trial?” Exactly that problem is now facing the Oxford vaccine in Britain.

An Oxford University vaccine trial has only a 50 per cent chance of success because coronavirus is fading so rapidly in Britain, a project co-leader has warned.

…Hill said that of 10,000 people recruited to test the vaccine in the coming weeks — some of whom will be given a placebo — he expected fewer than 50 people to catch the virus. If fewer than 20 test positive, then the results might be useless, he warned.