Scientists in the U.K. have launched a controversial trial that seeks to find out whether people previously infected with the coronavirus can catch COVID-19 again by deliberately exposing participants.

The U.K. became in February the first country in the world to give the go-ahead for so-called "challenge trials" in humans, in which volunteers are deliberately exposed to COVID-19 to advance research of the disease caused by the coronavirus.

The study launched on Monday differs from the one announced in February as it seeks to reinfect people who have previously had COVID-19 in an effort to deepen understanding about immunity and reinfection, rather than infecting people for the first time.

"The information from this work will allow us to design better vaccines and treatments, and also to understand if people are protected after having COVID, and for how long," said Helen McShane, a University of Oxford vaccinologist and chief investigator of the study. She added that the work would help to understand what immune responses protect against reinfection.

Scientists have used human challenge trials for decades to learn more about diseases such as malaria, flu, typhoid and cholera, and to develop treatments and vaccines against them.

The first stage of the trial will seek to establish the lowest dose of the coronavirus needed in order for it to start replicating in about 50% of participants while producing few to no symptoms. A second phase, starting in the summer, will infect different volunteers with that standard dose.

In Phase 1, up to 64 healthy participants, aged 18-30, who were infected with coronavirus at least three months ago will be reinfected with the original strain of SARS-CoV-2.

They will then quarantine for at least 17 days and be monitored, and anyone who develops symptoms will be given Regeneron monoclonal antibody treatment.