Coronavirus could be with us 'forever' if people can get re-infected, a British scientist has warned.
Professor Graeme Ackland, an academic at Edinburgh University, warned it could be 'horrific' if survivors aren't protected against the disease in the future.
The truth on Covid-19 immunity remains a mystery because the pathogen, known as SARS-CoV-2, has only been known to science for less than a year.
But leading experts believe the illness would be milder if a survivors gets reinfected because they would likely have some level of protection. Therefore, hospitalisations and deaths would not reach catastrophic levels, in theory.
Top scientists, including advisors to the Government, have previously said the virus will be in circulation for decades, like other similar coronavirus-like infections and seasonal illnesses.
Scientists do not yet know how long a person is immune to the coronavirus for, with several studies showing antibodies — proteins made by the immune system to fight off a disease in future — wane after just a few months.
If immunity is short-lived, it dashes hope of herd immunity building in the population — a natural way of wiping the virus out. But it doesn't rule out that people may be better protected if they get re-infected, suffering a much milder form of the illness.
But if survivors aren't protected from a severe bout of Covid a second time around, it suggests lockdowns will be necessary to save as many lives as possible until experts find a vaccine.
It comes as a study, which Professor Ackland was the lead author of, found that strict lockdowns are unlikely to cut deaths in the long run and may even increase them.
Strict lockdowns – particularly those curbing the activities of the young — could prolong the pandemic and cause hundreds of thousands of excess deaths over the next two years.
The alternative — shielding only the elderly and vulnerable and letting young people return to normality — may reduce the impact. But this strategy would rely on herd immunity, which has not been proven to be achievable, Professor Ackland admitted.
Ministers were last night under intense pressure to rethink the battle against the disease after the study cast fresh doubt over Covid restrictions.
The study, part-funded by an arm of government, came as a growing number of top scientists signed a declaration calling for life to be allowed to return to normal for all but the elderly and vulnerable. By this morning, more than 12,000 doctors and medical experts had endorsed the ‘Great Barrington Declaration’ that backs herd immunity.
Chief Medical Officer Professor Chris Whitty (right) said back in April: 'This disease is not going to be eradicated, it is not going to go away.' On at least three occasions, Sir Patrick Vallance, England's chief scientific adviser (left), said the aim is to 'build up some degree of herd immunity'. But has since profoundly denied that herd immunity was the target for Britain
Herd immunity has come back on scientists' radar as 'lockdown fatigue' builds in the general public, and ministers fight back against economy-crippling restrictions.
But the strategy falters in that it can't be said for certain that people who have had Covid-19 actually remain immune for a substantial amount of time.
Research has suggested that antibodies decline three or four months after infection. And some people may never develop antibodies at all, so the true number of cases will always be a mystery.
Herd immunity is a situation in which a population of people is protected from a disease because so many of them are unaffected by it - because they've already had it or have been vaccinated - that it cannot spread.
To cause an outbreak a disease-causing bacteria or virus must have a continuous supply of potential victims who are not immune to it.
Immunity is when your body knows exactly how to fight off a certain type of infection because it has encountered it before, either by having the illness in the past or through a vaccine.
When a virus or bacteria enters the body the immune system creates substances called antibodies, which are designed to destroy one specific type of bug.
When these have been created once, some of them remain in the body and the body also remembers how to make them again. Antibodies - alongside T cells - provide long-term protection, or immunity, against an illness.
If nobody is immune to an illness – as was the case at the beginning of the coronavirus outbreak – it can spread like wildfire.
However, if, for example, half of people have developed immunity – from a past infection or a vaccine – there are only half as many people the illness can spread to.
As more and more people become immune the bug finds it harder and harder to spread until its pool of victims becomes so small it can no longer spread at all.
The threshold for herd immunity is different for various illnesses, depending on how contagious they are – for measles, around 95 per cent of people must be vaccinated to it spreading.
For polio, which is less contagious, the threshold is about 80-85 per cent, according to the Oxford Vaccine Group.
WHICH COUNTRIES ARE PURSUING HERD IMMUNITY?
Herd immunity is considered a controversial route for getting out of the pandemic because it gives a message of encouraging the spread of the virus, rather than containing it.
When UK Government scientists discussed it in the early days of the pandemic, it was met with criticism and therein swept under the carpet.
The Chief Scientific Adviser Sir Patrick Vallance said at a press conference on March 12, designed to inform the public on the impending Covid-19 crisis: 'Our aim is not to stop everyone getting it, you can't do that. And it's not desirable, because you want to get some immunity in the population. We need to have immunity to protect ourselves from this in the future.'
Sir Patrick has since apologised for the comments and said he didn't mean that was the government's plan.
The Cabinet Office denied the claims made in the documentary and said: 'The Government has been very clear that herd immunity has never been our policy or goal.'
Meanwhile, unlike most European nations, Sweden never imposed a lockdown and kept schools for under-16s, cafes, bars, restaurants and most businesses open. Masks have been recommended only for healthcare personnel.
Sweden only introduced a handful of restrictions, including banning mass gatherings and encouraging people to work and study from home.
Dr Anders Tegnell, who has guided the nation through the pandemic without calling for a lockdown, claimed on July 21 that Sweden's strategy for slowing the epidemic, which has been widely questioned abroad, was working.
Dr Tegnell, who previously said the 'world went mad' with coronavirus lockdowns, said a rapid slowdown in the spread of the virus indicated very strongly that Sweden had reached relatively widespread immunity.
'The epidemic is now being slowed down, in a way that I think few of us would have believed a week or so ago,' he said.
'It really is yet another sign that the Swedish strategy is working.'
At the time Sweden's death toll was 5,646 which has now reached 5,892 almost three months later. When compared relative to population size, it has far outstripped those of its Nordic neighbours.
Covid-19 has only been around since the end of 2019, and so it has been impossible to tell so far whether people can catch the coronavirus twice.
But this has been the case in a small number of people, reports over the past few weeks have shown.
In August, two European Covid-19 survivors were reportedly re-infected after recovering from the disease; a Dutch patient who was old and had a weakened immune system and a Belgian woman who only had mild symptoms tested positive twice, local broadcasters claim.
It followed a landmark report of a Hong Kong man who was re-infected four and a half months after he was originally struck down. Genetic analysis revealed the 33-year-old's second bout of the disease, which he caught on a trip to Europe, was caused by a different strain of the virus.
Professor Ackland, a computer simulation expert, said it's 'possible' people can fall sick with the virus more than once, which is true for other coronaviruses such as the common cold.
On BBC Radio 4 Today programme this morning, he said: 'It's not my expertise, as I understand it, it is a very small number of cases. If it is true that people are continuously being re-infected, then the situation is just horrific, because this thing is going to be with us essentially forever.'
Other leading scientists have made the same doomsday predictions, including the Chief Medical Officer Professor Chris Whitty who said back in April: 'This disease is not going to be eradicated, it is not going to go away.
'So we have to accept that we are working with a disease with which we will be globally for the foreseeable future.'
Professor Sir John Bell, an immunologist at the University of Oxford, told MPs in July: 'The reality is that this pathogen is here forever, it isn't going anywhere,' he told MPs.
'Look at how much trouble they've had in eliminating, for example, polio, that eradication programme has been going on for 15 years and they're still not there.
'So this is going to come and go, and we're going to get winters where we get a lot of this virus back in action.'
However, even if re-infection is possible, it does not necessarily mean the coronavirus will be as destructive and take as many lives as seen in the first wave.
Paul Hunter, a professor of medicine at University of East Anglia, commented on the Hong Kong case of re-infection and said: 'It is quite likely that subsequent infections do not cause as severe an illness as the first episode because of some degree of residual immunity which may not be sufficient to stop the infection but be enough to reduce the risk of severe illness.'
In light of the impact lockdown has had, many scientists have argued that they are not feasible to continue, and a new approach will be needed moving forward to cap the devastating impact on people's livelihoods and the economy.
Research released by Edinburgh University on Wednesday shows that strict lockdowns – particularly those curbing the activities of the young – are unlikely to cut deaths in the long run and may even increase them.
It examined various lockdown-style scenarios and found that while they might protect hospitals, they could also prolong the pandemic and prevent the build-up of herd immunity.
It suggests that the strict lockdown imposed by Boris Johnson in March successfully