Human trial volunteers in good condition

Three volunteers are reportedly in good health after being intentionally exposed to the novel coronavirus during the first phase of a controversial United Kingdom COVID-19 trial.

The ultimate goal of the so-called human challenge trial is to test vaccines on infected individuals. In this initial stage, researchers are establishing the lowest viral dose needed to cause infection, by administering nasal droplets containing the virus in a range of concentrations.

The three participants have recently been released after two weeks in quarantine at the Royal Free Hospital in London, which is hosting the trial in collaboration with biotechnology company hVIVO and Imperial College London.

Researchers are set to perform further viral dosage tests on new groups of volunteers, before entering the vaccine testing stage of the study.

"We're pleased to confirm the first group of three healthy volunteers has now successfully completed the first stage of the trial," said Chris Chiu, who is an infectious disease specialist at Imperial College London, and chief investigator on the trial.

Challenge trials do however pose a number of ethical concerns. Some experts have questioned if enough is known about COVID-19 and its long-term effects in order to conduct challenge trials safely.

Others argue though the risk of medical complications among young and healthy volunteers is low, and such trials would benefit the wider population by speeding up vaccine development.