Young healthy adults in the UK are being invited to take part in a study that involves deliberately infecting them with coronavirus in a safe and controlled environment.

The aim of the human challenge trial is to establish the smallest amount of virus needed to cause infection.

This will give doctors greater understanding of Covid-19 and help support the pandemic response by aiding vaccine and treatment development.

Here is what we know about the trial:

– Who is being invited to volunteer?

The study will recruit up to 90 healthy volunteers between the ages of 18 and 30 with no previous history or symptoms of Covid-19, no underlying health conditions and no known adverse risk factors for Covid-19 such as diabetes or being overweight.

– Will participants be compensated?

Volunteers will receive around £4,500 to participate in the study which will involve some 17 days of quarantine and follow-ups over 12 months.

– What will the trial involve?

The first studies will start in a few weeks, and after registering their interests, people will be contacted and asked some basic questions to check basic eligibility.

They’ll be invited for a screening visit and the study will be discussed with them.

If the participant agrees the screening process will begin and they will have some blood tests and undergo basic physical examinations to make sure they are healthy and there is no unrecovered, unrecognised or undiagnosed health problem that might lead to more severe disease after they get the virus.

If all the tests are normal participants will be invited to a quarantine slot at the Royal Free Hospital, and they will have more intensive tests – like X-rays, and heart scans.

A couple of days after they arrive, assuming all those tests are fine, participants will receive a very small dose of the virus as drops in the nose in a very small volume of fluid – about a fifth of a millilitre.

They will then lie flat on their back for half an hour and then potentially they may be infected.

During this time participants will be in their own en-suite bedroom.

– How will they be monitored?

Medics and scientists will closely monitor the effect of the virus on volunteers and will be on hand to look after them 24 hours a day.

Study staff, wearing protective equipment, will conduct daily checks on participants, measuring their pulse and heart rate, blood pressure and so on.

Blood samples and swabs from the nose will be taken and people will be asked to test their sense of smell using scratch and sniff cards, as well as take part in some cognitive tests

After 14 days, if the participant is no longer shedding infectious virus they’ll be allowed to go home, and they will be seen every few months for the following year.

– Will people in the trial be treated for Covid-19?

At the start of the study researchers are intending to include remdesivir as a pre-emptive treatment.

As soon as people start shedding virus from their nose or start developing symptoms of Covid-19, they will be given the antiviral drug.

But the intention isn’t to keep remdesivir in this study design because researchers believe the challenge infections can be very mild and won’t require the drug, and adding remdesivir potentially gives additional complications.

The aim of the initial studies are not to produce any great severity of disease but to establish the smallest amount of virus needed to cause infection.

This initial study will also help doctors understand how the immune system reacts to coronavirus and identify factors that influence how the virus is transmitted, including how a person who is infected with the Covid-19 virus transmits infectious virus particles into the environment.

– What about future studies?

Data from the study will immediately facilitate the challenge model to be used for vaccine efficacy testing as well as to answer a wide range of fundamental scientific questions that are not feasible with traditional field trials.

These include exactly what type of immunological response is required to confer protection from reinfection.

– What coronavirus variant will people be infected with?

The study will initially use the version of the virus that has been circulating in the UK since March 2020 and has been shown to be of low risk in young healthy adults.

But the model could be adapted to new variants within months.

Researchers say it will take us approximately three to four months to manufacture a new variant of virus, should that be required.

They add that the differences between the strains is so small, and the variants are fundamentally causing the same type of disease, so there is a lot that can be learned that is generalisable across all different strains.

– Will the findings of the trial be applicable to the older, most vulnerable, members of the population?

Researchers say that younger adults have immune systems which are different from older adults and people who are more at risk of severe Covid-19, and so, it’s not always possible to directly extrapolate findings from this study situation to patients in the community.

However, they say the findings from the challenge studies will provide information about the fundamentals of the immune response and protection.

And if they can identify the immune factors which are responsible for protection, then they can bridge into older people, where if they can induce the same kinds of immune markers, they can be much more confident that vaccines and other treatments are going to also be effective.