UK will run world’s first controversial Covid-19 challenge trial

Britain has become the first country in the world to green light a controversial study where volunteers are deliberately infected with coronavirus.

The ‘human challenge trial’ will start next month in London after sealing approval from the UK’s clinical research ethics body today.

Researchers will purposefully expose up to 90 healthy adult volunteers under the age of 30 to a dose of SARS-CoV-2, the virus that causes Covid-19.

The study, which is being backed by £33.6million of taxpayer cash, will seek to establish how much viral load it takes for a person to get infected with the disease.

This has been one of the burning questions during the pandemic. It’s thought that the amount of virus particles someone inhales determines how sick they will be.

The trial, which is being led by Imperial College London, will also be used to accelerate the approval of promising upcoming vaccines. Standard human vaccine studies currently take months because scientists need to wait for volunteers to catch the virus naturally.

Challenge trials are commonly deployed by scientists trying to develop a vaccine and have been used in malaria, typhoid and flu. 

But, unlike those illnesses, there is no proven treatment for people with mild coronavirus, so there is little to stop the participants falling seriously ill.

British scientists will be the first in the world to carry out a controversial study in which healthy volunteers are infected with coronavirus , according to reports 

Business Secretary Kwasi Kwarteng said: ‘While there has been very positive progress in vaccine development, we want to find the best and most effective vaccines for use over the longer term. 

‘These human challenge studies will take place here in the UK and will help accelerate scientists’ knowledge of how coronavirus affects people and could eventually further the rapid development of vaccines.’ 


Challenge trials involve intentionally infecting healthy people with viruses then giving them a shot of a vaccine to see if the jab can clear the virus.

These studies have been done with many illnesses, including malaria, typhoid and flu. 

But, unlike those illnesses, there is no treatment that prevents someone from falling badly ill with Covid-19.

Because of the ethical implications, so far none of the 23 clinical trials of coronavirus vaccines currently being carried out around the world have used the controversial study method.

Instead they are relying on participants who have caught the disease by accident in the community.

But because international lockdowns have been so effective, the number of people actually contracting the illness in the public is falling.

For this reason many studies are grinding to a halt.

Many projects – including Oxford University’s – have had to move their trials abroad where infection rates are higher. 

Oxford is now testing he vaccine on 6,000 people in Brazil and South Africa – and hopes to have conclusive results by the end of the year.

This would mean a jab could be rolled out in early 2021. 

Researchers are encouraging people aged between 18 and 30 years old, who are at the lowest risk of falling seriously unwell with Covid, to volunteer for the study.  

Triallists will only be accepted if they have no previous history or symptoms of Covid-19, no underlying health conditions and no known risk factors for the disease, such as being overweight or smoking. 

They will be infected with the original strain of coronavirus which has been circulating in the UK since last February. They will also be monitored 24 hours a day.

That strain was the dominant one across the country until this winter when it was overtaken by the highly-infectious, more deadly Kent variant. It now accounts for fewer than 20 per cent of new infections.

It’s unclear why researchers are not assessing the Kent strain, which is the more immediate threat to the UK’s pandemic response. 

Any new treatments or vaccines will need to be able to target this variant if they are to gain approval from Britain’s medical watchdog.

However, all current Covid medicines and vaccines proven to work on the original strain have shown to be effective on the Kent one, too.    

The challenge study is being delivered by a partnership between the No10’sx Vaccines Taskforce, Imperial College London, the Royal Free London NHS Foundation Trust and drug researcher hVIVO.

The research will take place in the Royal Free’s quarantine clinics in London which are specifically designed to contain infectious diseases.

The study will initially aim to help doctors understand how the immune system reacts to different levels of coronavirus and how a person who is infected with Covid-19 virus transmits infectious particles into the environment. 

But it’s hoped that vaccine candidates shown to be safe in early studies will then be trialled on the participants to accelerate their approval. 

Vaccines are normally tested using two groups of people, both of which need to contract the disease naturally, with one given the vaccine and the other used as a control. 

Traditional clinical trials require tens of thousands of participants to boost the chance of some of them being infected with coronavirus in the community.

But, in challenge trials, the pool of volunteers can be much smaller because every person is guaranteed to be infected with the disease.

Interim Chair of the Vaccines Taskforce Clive Dix said ‘We have secured a number of safe and effective vaccines for the UK, but it is essential that we continue to develop new vaccines and treatments for Covid-19. 

‘We expect these studies to offer unique insights into how the virus works and help us understand which promising vaccines offer the best chance of preventing the infection.’

Scientists will need to decide on a dose that infects the volunteer without causing serious illness.

This has previously been a sticking point because experts are still divided about what qualifies a ‘safe dose’ of the virus.

Some people infected with large amounts of the disease experience no symptoms at all, while others fall seriously unwell with much smaller amounts, although this is mostly the elderly and those with weakened immune systems.

It is also essential for there to be medication on standby that can prevent serious illness in participants.

So far, only a few steroids and anti-inflammatories have been scientifically proven treatment for Covid-19. But they only work on people who are extremely unwell.

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