Researchers at the University of Oxford have launched a trial that will deliberately expose people who have already had Covid to the coronavirus again to study the level of immune protection needed to prevent reinfection (assuming reinfection is possible). It is hoped that the study will aid the development of treatments and vaccines. The Guardian has the story.
The first human challenge trials for Covid began this year, with the study – a partnership led by researchers at Imperial College London among others – initially looking at the smallest amount of virus needed to cause infection among people who have not had Covid before.
Now researchers at the University of Oxford have announced that they have gained research ethics approval for a new human challenge trial involving people who have previously had coronavirus. Recruitment is expected to start in the next couple of weeks.
“The point of this study is to determine what kind of immune response prevents reinfection,” said Helen McShane, a Professor of Vaccinology at the University of Oxford, and Chief Investigator on the study.
McShane said the team would measure the levels of various components of participants’ immune response – including T-cells and antibodies – and then track whether participants became reinfected when exposed to the virus.
Participants 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. As well as having previously had a positive Covid PCR test, they must also have antibodies to Covid. Given the timing criteria, McShane said it was likely most participants would have previously been infected with the original strain of the virus.
The first phase of the trial will initially involve 24 participants split into dose groups of three to eight people who will receive, via the nose, the original strain of coronavirus. The idea is to start with a very low dose and, if necessary, increase the dose – up to a point – between groups…
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 vaccines which produce the required level of immunity – as determined by this study – could have their licensing fast-tracked without trials of thousands of people, according to Professor McShane.
If we can determine the level of immune response above which an individual cannot be infected, then that will help us determine whether new vaccines will be effective without necessarily having to test them in phase three efficacy trials.
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