United Kingdom plan to be first to run "human challenge" Covid trials

Henrietta Brewer
October 22, 2020

The Human Challenge Programme is a partnership between Imperial College London, the Department for Business, Energy and Industrial Strategy (BEIS), hVIVO, a leading clinical company with expertise in viral human challenge models, and the Royal Free London NHS Foundation Trust.

"In this initial phase, the aim will be to discover the smallest amount of virus it takes to cause a person to develop Covid-19", Imperial College said in a statement on Tuesday. "It's not to say that we wouldn't still need phase 3 studies, but we would obviously be in a much better position if we could say that when we vaccinate healthy young people with this vaccine and then challenge them with virus, it's 80% effective or 60% effective or 20% effective or not effective at all".

"...perhaps the main limitation is that the challenge studies can ethically only select healthy adult volunteers - not children or the elderly, or those vulnerable groups with diabetes, hypertension, chronic heart, lung, kidney disease, or pregnant women or immunocompromised people - so the interpretation of such studies will, ironically, be only applicable to those who least need the protection", notes Tang. Possible candidates include vaccines that have proven themselves in large, phase 3 trials or ones that may be earlier in their development but look promising.

The government says trials that deliberately infect people with a virus have been conducted for influenza and other pathogens.


Researchers in the United Kingdom are set to deliberately infect young, healthy volunteers with SARS-CoV-2. Antibodies are nearing approval, but it is unclear how well they work as treatments for COVID-19 or whether they will be available in the U.K.by the time the first stage of the challenge trial starts in January.

Researchers would then study how vaccines work in the body to stop COVID-19.

The volunteers will be infected with the virus through the nose and monitored around the clock.

From a scientific perspective, infecting people with a known dose of the virus can help researchers be more precise about evaluating and comparing people's immune responses to different vaccines.


Vaccine Taskforce chair Kate Bingham said the research will improve our understanding of the virus and will help in making decisions about research.

A spokeswoman for the World Health Organization (WHO) said there are "very important ethical considerations" when approaching human challenge trials. Belgium invested €20 million in a facility to run challenge studies early in the pandemic and Colorado State University has a USA government contract to develop SARS-CoV-2 strains that could be used in human challenge studies.

No severe adverse reaction has been reported among the volunteers, the official said, adding that preliminary results show that the vaccines are generally safe and have minor side effects such as pain and bruising at the injection site, as well as temporary low-grade fever.

The studies will be carried out at the Royal Free Hospital in London, and will involve young, healthy participants that have been carefully selected by researchers - and who will be compensated for their involvement.


Danica Marcos, 22, a recent university graduate now doing volunteer work with homeless people, is hoping to take part.

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