A scientist heading the human trials for a possible COVID-19 vaccine has said volunteers are “critically important” to their research.

Speaking on the BBC’s Radio4 programme, Professor Robin Shattock, who heads Imperial College London’s vaccine team, said researchers are looking for more healthy participants to take part in their clinical trials.

Prof Shattock, who is head of mucosal infection and immunity at Imperial, said: “We are starting with a very few number of volunteers so we don’t want people to be disappointed if they are not immediately engaged in clinical trial. But we are looking for those volunteers and they are critically important.”

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The first phase of the clinical trials is set to begin this week with 300 people, and a further trial involving involving 6,000 people is planned for October. If these prove successful, Imperial hopes the coronavirus vaccine could be distributed in the UK and abroad early next year.

Their RNA vaccine works by delivering genetic instructions to muscle cells to make the “spike” protein on the surface of coronavirus. The presence of this protein provokes an immune response, offering protection against COVID-19.

Prof Shattock told Radio 4: “The first part of the clinical development is to check that it is really safe because it is going to be used in the general population.”

He added that checks would also be made to ensure that the vaccine candidate “induces the right kind of immune response that we would predict would be protective”.

Prof Shattock continued: “We will move into large-scale efficacy trials in October. Then it’s a numbers game. It depends on how many infections are ongoing in the community.

“If we see a lot of infection, we may get a result fairly quickly. If there are very few infections, obviously it will take a lot longer to get enough data to be able to prove that the vaccine works or not.”

Healthy people can sign up to volunteer for the Imperial College trial at imperial.crf.nihr.ac.uk.

How do scientists develop vaccines for new viruses?

Vaccines work by fooling our bodies into thinking that we’ve been infected by a virus. Our body mounts an immune response, and builds a memory of that virus which will enable us to fight it in the future.

Viruses and the immune system interact in complex ways, so there are many different approaches to developing an effective vaccine. The two most common types are inactivated vaccines (which use harmless viruses that have been ‘killed’, but which still activate the immune system), and attenuated vaccines (which use live viruses that have been modified so that they trigger an immune response without causing us harm).

A more recent development is recombinant vaccines, which involve genetically engineering a less harmful virus so that it includes a small part of the target virus. Our body launches an immune response to the carrier virus, but also to the target virus.

Over the past few years, this approach has been used to develop a vaccine (called rVSV-ZEBOV) against the Ebola virus. It consists of a vesicular stomatitis animal virus (which causes flu-like symptoms in humans), engineered to have an outer protein of the Zaire strain of Ebola.

Vaccines go through a huge amount of testing to check that they are safe and effective, whether there are any side effects, and what dosage levels are suitable. It usually takes years before a vaccine is commercially available.

Sometimes this is too long, and the new Ebola vaccine is being administered under ‘compassionate use’ terms: it has yet to complete all its formal testing and paperwork, but has been shown to be safe and effective. Something similar may be possible if one of the many groups around the world working on a vaccine for the new strain of coronavirus (SARS-CoV-2) is successful.

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Sara RigbyOnline staff writer, BBC Science Focus

Sara is the online staff writer at BBC Science Focus. She has an MPhys in mathematical physics and loves all things space, dinosaurs and dogs.