THE world hasn’t built up anywhere near the amount of coronavirus immunity needed for herd protection, warns the World Health Organisation.
Despite there being more than 22.3million Covid-19 cases across the globe, not enough people have developed antibodies to stop the spread, it adds.
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Soldiers from the 4th Military Region of the Brazilian Armed Forces take part in the cleaning and disinfection of a market in the Belo Horizonte, August 18[/caption]
Herd immunity is typically best achieved with vaccination.
Most scientists estimate that at least 70 per cent of the population must have antibodies to prevent an outbreak.
But some experts have suggested that if even half the population had immunity, there might be a protective effect.
However, WHO’s emergencies chief Dr Michael Ryan appeared to quash that theory at a press briefing.
On Tuesday, he told reporters that we should not live in hope of achieving natural herd immunity.
Dr Ryan said: “As a global population, we are nowhere close to the levels of immunity required to stop this disease transmitting.
“This is not a solution and not a solution we should be looking to.”
Dr Bruce Aylward, a senior adviser to WHO’s director-general, added that any mass immunisation campaign with a Covid-19 vaccine would aim to cover far more than 50 per cent of the worlds population.
He said: “We don’t want to be wrong.
“You want to plan to get high coverage and not get lulled into a dangerously seductive suggestion that (the herd immunity threshold) could be low.”
Most studies conducted to date have suggested only about ten to 20 per cent of people currently have antibodies against the coronavirus.
In early July, Dr Ryan said it was unlikely that the disease would be completely eliminated.
“In the current situation it is unlikely we can eradicate this virus,” he said.
The expert added that, by extinguishing clusters of infection, the world could “potentially avoid the worst of having second peaks and having to move backwards in terms of lockdown”.
Herd immunity refers to where enough people in a population have natural protection against an infection to be able to effectively stop that disease from spreading.
Scientists have written about “host resistance” to the new virus and a possibly lower threshold of herd immunity needed to fend off further devastating Covid-19 outbreaks.
Their paper, published on Medrxiv, says that it is widely believed the threshold needed to enjoy herd immunity against the new disease is more than 50 per cent.
But, the research suggests that if just 20 per cent of the UK’s population has in-built resistance to Covid-19, a second wave is not inevitable.
The Oxford Uni study suggests the epidemiological limit to reach herd immunity “may be greatly reduced if a fraction of the population is unable to transmit the virus”.
This is feasible, they add, if people have inbuilt “resistance or cross-protection from exposure to seasonal coronaviruses”.
Scientists at the Liverpool School of Tropical Medicine and the University of Strathclyde found England – as well as Portugal and Spain – to have herd immunity in the range of 10 to 20 per cent.
A new coronavirus testing facility inside Heathrow Airport’s Terminal 2[/caption]
People enjoy a music party at a swimming pool at Wuhan Maya Beach Park, China[/caption]
It means around 3.4 million people in the country could have had Covid-19 – far greater than the UK’s official tally of 320,286.
Londoners were most likely to have been infected, with results suggesting that 13 per cent of people in the capital had antibodies.
This compared to less than three per cent in the South West of England.
And a study by researchers at the University of Sussex indicates more than 40 per cent may be immune.
Professor Peter Krüger, a physicist and data scientist at the University of Sussex, told Newsweek that the infection rate will be much higher in some groups, such as key workers, and lower in others.
But in Sweden, the county’s top coronavirus expert has been blasted for appearing to ask whether a higher death rate was a fair price for herd immunity, bombshell emails show.
Anders Tegnell decided against a lockdown in the country which has suffered a higher death toll than its Scandinavian neighbours.
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Messages sent by Mr Tegnell, and obtained by journalists through freedom of information laws, appear to show him discussing keeping schools open to encourage herd-immunity.
The publication of the emails, which date back five months, has sparked criticism of Sweden’s liberal approach to the pandemic.
Following the release of the email exchange, Mr Tegnell said: “Keeping schools open to gain immunity was never relevant.”
A woman wears a protective face mask in Stockholm, Sweden[/caption]