UK launches human challenge trial on COVID-19 reinfection

19-Apr-2021 - Last updated on 19-Apr-2021 at 12:54 GMT

Pic:getty/designcells

A human challenge trial has been launched in the UK to investigate what happens when people who have already had COVID-19 are infected a second time.

The aim of the study is to see what kind of immune response is required to stop people being re-infected; as well as investigate how the immune system reacts to re-exposure.

As a challenge trial, the study will purposefully infect healthy volunteers with the virus in a carefully controlled environment.

The results of the trial, led by the University of Oxford, will help inform vaccine development and effective treatments.

Two phases

The first phase of the study will start this month. This will establish the lowest dose of virus which can take hold and start replicating but produce little or no symptoms (in the trial, this will be based on virus which takes hold in approximately 50% of participants).

This phase will cover up to 64 healthy participants between the ages of 18 and 30 years old who have previously been infected with COVID-19. They will be re-exposed to the original strain from Wuhan. Medical tests will include CT scans of the lungs and MRI scans of the heart. Any participants who develop symptoms will be treated with Regeneron’s monoclonal antibody treatment.

The second phase of the study, starting in the summer, all participants will be infected with the standardised dose of virus ascertained from Phase 1.

The researchers note that a challenge study will allow them to measure virus loading, responses and their duration: which is hard to measure when occurring naturally as the point of infection is not often known.

“Challenge studies tell us things that other studies cannot because, unlike natural infection, they are tightly controlled,” said Helen McShane, Professor of Vaccinology at the Department of Paediatrics, University of Oxford and Chief Investigator on the study.

“When we re-infect these participants, we will know exactly how their immune system has reacted to the first COVID infection, exactly when the second infection occurs, and exactly how much virus they got.

“We’re really interested in asking what flavor of immune response – antibodies, t-cells – correlate with protection.

“It will be a tool to allow us to develop next generation vaccines, better vaccines, better monoclonal antibodies as treatments.”