London, April 19 : Researchers at the University of Oxford have gained ethical approval for a new human challenge trial that aims to check the immune response needed to protect people against reinfection. As part of the trial, healthy people will be deliberately exposed to a disease-causing organism in a carefully controlled manner, The Guardian reported. The method has proved valuable in understanding and tackling myriad conditions from malaria to tuberculosis and gonorrhoea, the researchers said. Recruitment for the trial is expected to start in the next couple of weeks, the report said. "The point of this study is to determine what kind of immune response prevents reinfection," Helen McShane, Professor of vaccinology at the University of Oxford, and chief investigator on the study, was quoted as saying to the Guardian. Levels of various components of immune response -- including T-cells and antibodies -- will be measured and then tracked to see how it reinfects when people are exposed to the virus, McShane said. Besides determining the level of immune response, the trail will also help understand the efficacy of vaccine. People participating in the trial must be healthy, at low risk from Covid, aged between 18 and 30, and must have been infected with the coronavirus at least three months before joining the trial. Besides a positive Covid PCR test, they must also have antibodies to Covid. In the first phase, the team will involve 24 participants split into dose groups of three to eight people. The participants will receive the original strain of coronavirus, via the nose. Once 50 per cent participants get infected with mild disease, it will be administered to 10-40 other participants to confirm the dose. The second phase of the study -- expected to start in the summer -- will involve a new group of participants and will study closely their immune response before and after exposure to the virus, as well as the level of virus and symptoms in those who become reinfected, the report said. If the participants reinfection is confirmed, or symptoms develop, in either phase of the trial, they will be given a monoclonal antibody treatment. The participants will be followed up for 12 months. They will also receive monetary assistance, the report said. /IANS