Challenging Times?

The World Health Organisation has reportedly joined other groups in giving 'qualified support' to the concept of doing challenge trials for developing a vaccine for Covid-19 (https://www.theguardian.com/science/2020/may/08/who-conditionally-backs-covid-19-vaccine-trials-that-infect-people). Challenge trials involve giving the infective agent to healthy research subjects who would then get trial vaccines or placebo. Such tests would be one way of speeding up the development of an effective and safe vaccine. Such trials have been used for other diseases (e.g. malaria) but there are two particular problems with Covid-19. These are a) we currently have no idea what constitutes a 'safe' dose of the virus and b) there are (unlike in the case of malaria) no current cures that can be given if a patient shows an extreme response. Having said that, the risk of death for young, fit participants (who would clearly be used in initial tests) is very low and the benefits to human health could be immense.