The World Health Organisation has condemned the “dangerous” concept of herd immunity for managing the coronavirus pandemic.
Dr Michael Ryan, executive director of the WHO’s health emergencies programme said it was wrong to think that countries can “magically” make their populations immune to Covid-19.
It was reported in March that the UK government was hoping to achieve herd immunity by allowing the virus to make its way through the population. Health secretary Matt Hancock denied it was ever part of government strategy.
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Dr Ryan told a press briefing in Geneva: “Humans are not herds, and, as such, the concept of herd immunity is generally reserved for calculating how many people will need to be vaccinated and the population in order to generate that effect.”
The WHO director added: “So I do think this idea that ‘maybe countries who had lax measures and haven’t done anything will all of a sudden magically reach some herd immunity, and so what if we lose a few old people along the way?’ This is a really dangerous, dangerous calculation.”
Herd immunity is an epidemiological concept usually reserved for describing how a population is protected from a disease depending on the levels of people vaccinated.
For instance, when between 90 per cent and 95 per cent of the population is vaccinated against measles, this should be enough to protect others who are unable to get an inoculation – such as babies before they reach the age at which they can be immunised.
Sir David King, the former chief scientific adviser to the UK government suggested at the end of April that ministers could still secretly be seeking to create herd immunity, having “softened” their tests for starting to relax restrictions.
“Maybe we are going for herd immunity? In other words, maybe the policy is to allow the virus to spread so that we have a large proportion of our population who have antibodies and, at that point, we will all be resistant to the virus and the lockdown can be removed?”
Dr Ryan said he was hopeful that Germany and South Korea would be able to suppress new clusters of the virus and praised their test and tracing surveillance programmes, which he said was key to avoiding large second waves.
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“Now we are seeing some hope as many countries exit these so-called lockdowns,” he told the international news conference, adding that “extreme vigilance” was still needed.
“Responsible member states will look at all their population – they value every member of society and they try to do everything possible to protect health while at the same time, obviously, protecting society and protecting the economy and other things,” said Dr Ryan.
He added: “This is a serious disease, this is public enemy number one, we have been saying it over and over and over and over again.”
Dr Maria Van Kerkhove, technical lead of the WHO’s Covid-19 response, said preliminary data from studies has shown that very low levels of the population have actually been infected with the illness.
“There seems to be a consistent pattern so far, that a low proportion of people have these antibodies,” she told the press conference in Geneva.
“And that is important … because you mentioned this word ‘herd immunity’, which is normally a phrase that’s used when you think about vaccination.
“You think what amount of the population needs to have an immunity to be able to protect the rest of the population? We don’t know exactly what that level needs to be for Covid-19. But it certainly needs to be higher than what we’re seeing in seroprevalence studies.”
Seroprevalence refers to the level of a pathogen in a population, as measured in blood serum.
Dr Van Kerkhove added: “What the sero-epidemiologic studies indicate to us is that there’s a large portion of the population that remains susceptible.”
Additional reporting by agencies
