Oxford human challenge trial to re-expose healthy volunteers to Covid

Helen McShane, Professor of Vaccinology at the Department of Paediatrics, University of Oxford, and Chief Investigator on the study said the findings would mean that scientists could look at “every single aspect of immunity we can possibly study” including antibodies and T cells, to establish what was needed to prevent infection, and how long it lasted. 

She said: “The point of this study is to determine what kind of immune response prevents reinfection. 

“It’s the first time anyone with previous SARS Co-V-2 infection has been deliberately infected in this way.”

“We will be interrogating the baseline immune response in these healthy volunteers, and then looking at whether or not we can reinfect, we will be looking at the quality of that immune response, we’ll look at antibodies, we’ll look at T-cells, we’ll look at every single aspect of immunity we can possibly study, we will look at the quantity of that immune response. And of course, critically, we will also look at durability.”

In the first phase of the trial, starting later this month, scientists will seek to establish the lowest dose of virus which is enough to take hold and start replicating in at least half of those who have previously had Covid. The second phase, in the summer, will see what happens to participants given a standard dose of virus. 

Establishing the level of immune response which prevents infection could help scientists establish whether future vaccine would be effective, with fewer trials, Prof McShane suggested.

Further trials could see how participants respond to new variants, with the South African variant among those under consideration, she said. 

“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,” she said.

A similar study is already ongoing, led by Imperial College London, where volunteers without a history of Covid are being infected with the virus to test vaccines and treatments.