First coronavirus vaccine will not be a 'silver bullet', is unlikely to stop people catching the disease and may only reduce symptoms, scientists warn government

• Experts advising the government say that it may only reduce people's symptoms
• They said it may be partially effective and stressed caution when it is rolled out
• Chief Medical Officer Chris Whitty has set the bar at 40 to 60 per cent efficiency
• Oxford University leading charge for vaccine set minimum target of 50 per cent
• They said one that can reduce symptomatic Covid cases by half will be valuable

The first coronavirus vaccine will not be a 'silver bullet' and is unlikely to stop people catching the disease, scientists have warned in a blow to Britain's hopes of avoiding a second draconian lockdown.

Experts advising the government said it may only reduce people's symptoms and be partially effective, as they stress the need for caution when a jab is eventually found to work and is rolled out.

England's Chief Medical Officer Professor Chris Whitty has set the bar at 40 to 60 per cent efficiency - similar to the flu jab. But the Oxford University team leading the charge for a vaccine set a minimum target of 50 per cent.

They said one that can cut symptomatic coronavirus cases by half would be hugely valuable. But it would mean millions of Britons would, in theory, still be vulnerable to suffering the life-threatening disease. 

Boris Johnson has previously acknowledged that a mass-testing programme is the UK's 'only hope' of avoiding another national lockdown, in the absence of a vaccine. It is why Number 10 has pledged to eventually carry out 10million tests a day.

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Experts advising the government said it may only reduce people's symptoms and be partially effective as they stress the need for caution when it is rolled out (file photo)

The government hopes a jab will be ready in the first half of next year, but there will still need to be measures in place while people are injected.

The severity of the restrictions - such as social distancing rules - will hinge on how successful the vaccine is.

The first jab will likely have to be followed up with a booster around a month later and some people may need two different vaccines to trigger their immune system.

A government source told the Times: 'It depends on what we find. It seems the most likely outcome in the short to medium term is to find a vaccine, or two doses of a vaccine, that reduces the severity of symptoms. It's possible we might need several vaccines, but we are backing a lot of horses.'

Head of vaccines at the Wellcome Trust Charlie Weller said the first vaccine will probably need to be phased in alongside other restrictions.

He added: 'We need to manage everyone's expectations on what these first frontrunners of vaccines can actually do.

'There's a lot of hope, understandably, resting on a vaccine that is going to be this wonderful one dose [that will give] full lifetime immunity and move us back to normality the next day, but it's not going to be the perfect solution; it's not going to be the silver bullet.'

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Chief Medical Officer Professor Chris Whitty (pictured with Chief Scientific Adviser Sir Patrick Vallance this week) has set the bar at 40 to 60 per cent efficiency - similar to the flu jab

It was revealed yesterday British scientists will be the first in the world to carry out a controversial study where volunteers are deliberately infected with coronavirus.

The 'challenge trial' — which could rapidly accelerate the approval of experimental jabs — is said to be set to begin in January at a clinic in east London.

Participants will be infected with a dose of SARS-CoV-2, the virus that causes Covid-19, a month after being jabbed with a vaccine, according to the Financial Times.

The study, reportedly funded by the government, could help drug-makers test their Covid-19 vaccines without having to wait for volunteers to naturally catch the virus.

Between 100 and 200 participants are expected to be recruited for the trial, which is being run by a US advocacy group that has campaigned for human challenge trials.

It is unclear which vaccine candidate will be tested, but drug giants AstraZeneca and Sanofi have both insisted they are not taking part.

MailOnline has approached Imperial College London — Britain's other jab front-runner — for comment about its involvement.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 nothing to stop the participants falling seriously ill. 

The vaccine to be tested in the project has not been named, and organisers are said to have earmarked a quarantine clinic run by hVivo in Whitechapel, London, to carry out the trials.

Drug researcher hVivo is linked to Queen Mary University of London, while Imperial College London is understood to be the project's academic leader.

Around 2,000 potential volunteers have signed up to take part in challenge studies in the UK.

They have done so through 1Day Sooner, a US-based advocacy group which is made up of 100 leading experts including Nobel Prize-winning scientists.

The group campaigns for Covid-19 infection trials and has enlisted 37,000 people worldwide.

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hVivo's laboratory in Whitechapel, east London (under construction) where the initial trials are set to be held in

It is currently petitioning for the controversial trials to be signed off by health regulators in the UK.

Any trials conducted in Britain have to be approved by the Medicines and Healthcare products Regulatory Agency (MHRA).

The MHRA told the FT: 'Human challenge trials can be helpful for the development of vaccines and can provide early evidence of clinical efficacy, particularly when there are low rates of infection of the virus in the population.

'The safety of trial participants is our top priority and any proposal from a developer to include a human infection challenge as part of a clinical trial for development of a vaccine would be considered on a benefit-risk basis, with risks monitored for and minimised in the proposed trial design.'

WHAT ARE CHALLENGE TRIALS? 

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. 

Scientists behind the challenge trial will have to select and purify a strain of coronavirus that is currently circulating among the UK population.

They will then 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, which only jumped to humans earlier this year.

Some people infected with large amounts of the disease experience no symptoms at all, while others fall seriously unwell with much smaller amounts - particularly 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 - another roadblock in getting the trials approved. 

So far, only a few steroids have been scientifically proven treatment for Covid-19 - but they are only effective in the sickest of patients and do nothing for those with moderate illness.

The London trial will initially use remdesivir, an antiviral drug which has shown promise in preliminary studies. But there is no concrete evidence to prove it works.

It is not clear if participants will be of a certain age. Younger people are much less vulnerable to the disease than over-60s.

Those who take part in the trial are likely to be paid upwards of £4,000, according to the FT.

People who participate in hVivo's challenge trials of influenza receive up to £3,750.

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. 

Both of Britain's leading vaccine candidates are using the conventional methods, but they are being held up because so few people were being exposed to the disease during summer.

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. 

Reacting to the news, Dr Claire Waddington, clinical lecturer in infectious diseases at the University of Cambridge, said: 'Challenge trials are well established as a way to accelerate the development of vaccines for a wide range of infections.  

'As we gain more understanding of Covid-19, we are increasingly in a position to identify those people for who Covid-19 infection is a mild illness, and these people could safely participate in a controlled human infection study after a thorough medical assessment and consent process. 

'Such a model could give us some extremely useful information on how the immune system responds to Covid-19 and what responses are protective, as well as providing a model for early testing of candidate vaccines.'

WHICH VACCINES HAVE THE UK SECURED DEALS FOR? 

1. GlaxoSmithKline and Sanofi Pasteur: 60million doses 

The Government revealed on July 29 it had signed a deal with pharmaceutical giants GlaxoSmithKline (GSK) and Sanofi Pasteur

If the vaccine proves successful, the UK could begin to vaccinate priority groups, such as frontline health and social care workers and those at increased risk from coronavirus, as early as the first half of next year, the Department for Business, Energy & Industrial Strategy (BEIS) said. 

Human clinical studies of the vaccine will begin in September followed by a phase 3 study in December. 

The vaccine is based on the existing technology used to produce Sanofi's seasonal flu vaccine. Genetic material from the surface protein of the SARS-CoV-2 virus is inserted into insect cells - the basis of Sanofi's influenza product - and then injected to provoke an immune response in a human patient.  

2. AstraZeneca (manufacturing University of Oxford's): 100million

AstraZeneca, which is working in partnership with Oxford University, is already manufacturing the experimental vaccine after a deal was struck on May 17.

Professor Sarah Gilbert, who is leading the Oxford team, is confident the jab could be ready for the most vulnerable people by the end of the year.

Her comments came after the results from the first phase, published in The Lancet on July 20, showed promise.

The team have genetically engineered a virus to look like the coronavirus - to have the same spike proteins on the outside - but be unable to cause any infection inside a person. This virus, weakened by genetic engineering, is a type of virus called an adenovirus, the same as those which cause common colds, that has been taken from chimpanzees. 

3.  BioNTech/Pfizer: 30million 

US drug giant Pfizer - most famous for making Viagra - and German firm BioNTech were revealed to have secured a deal with the UK Government on July 20.

It reported positive results from the ongoing phase 2/3 clinical trial of one called BNT162b1 on July 1.  The company is still running phase 2 trials at the moment.

Pfizer's vaccine is one called an mRNA vaccine, which do not directly inject bits of the virus into the body but send genetic material.

mRNA vaccines programme the body to produce parts of the virus itself by injecting the body with a molecule that tells disease-fighting cells what to build. The immune system then learns how to fight it.

4. Valneva: 60million 

The Government has given Valneva — whose vaccine is understood to be in the preclinical stages of development — an undisclosed amount of money to expand its factory in Livingston, Scotland. 

While the Government revealed a 60million dose deal on July 20, the company said it had reached agreement in principle with the UK government to provide up to 100million doses. 

Valneva's jab is an inactivated whole virus vaccine, meaning it injects a damaged version of the coronavirus itself into the body.

The virus has been destroyed in a way that makes it unable to cause infection, but the body still recognises it as a dangerous intruder and therefore mounts an immune response which it can remember in case of a real Covid-19 infection. 

5. Janssen (Johnson & Johnson): 30million

The Government has agreed to buy 30million doses of a vaccine made by Janssen if it works.

Officials have agreed to help the company in its development of the jab by part-funding a global clinical trial. The first in-human trials of Janssen's jab began in mid-July and are being done on adults over the age of 18 in the US and Belgium.

The jab is named Ad26.COV2-S, recombinant, and is a type of jab called a viral vector recombinant vaccine.

Proteins that appear on the outside of the coronavirus are reproduced in a lab and then injected into the body to stimulate an immune reaction.

The 'Ad' part of the vaccine's name means it works using an adenovirus - a virus best known for causing the common cold - as a vehicle to transport the coronavirus genetics into the body.

6. Novavax: 60million

Britain has ordered 60million doses of a vaccine being developed by the US-based company Novavax. It will help to fund late-stage clinical trials in the UK and also boost plans to manufacture the vaccine in Britain.

Novavax's jab, named NVX-CoV2373, showed positive results in early clinical trials.

It produced an immune response in 100 per cent of people who received it, the company said, and was safe and 'generally well-tolerated'. 

Novavax's candidate is also a recombinant vaccine and transports the spike proteins found on the outside of the coronavirus into the body in order to provoke the immune system. 

7. Imperial College London: Unknown quantity

Imperial College London scientists are working on Britain's second home-grown hope for a jab. The candidate is slightly behind Oxford's vaccine in terms of its progress through clinical trials, but is still a major player.

The UK Government is understood to have agreed to buy the vaccine if it works but details of a deal have not yet been publicised. 

Imperial's jab is currently in second-phase human trials after early tests showed it appeared to be safe. 

Imperial College London will try to deliver genetic material (RNA) from the coronavirus which programs cells inside the patient's body to recreate the spike proteins. It will transport the RNA inside liquid droplets injected into the bloodstream.