The battle against Covid-19 has seen the concept of herd immunity become widely misunderstood, misrepresented, and turned into a deeply dangerous idea. Now, with the White House starting to toy with the idea of achieving herd immunity in the US through infections rather than a vaccine, there are fresh warnings from scientists and public health experts that this idea isn’t just unscientific, it’s brutally unethical.
In its purest sense, herd immunity is used in the context of vaccinations. When the vast majority of a population are immune against a disease, such as after receiving a vaccine, the remaining minority of the population will also have a reduced risk of catching the infection. This is because immune individuals are unlikely to contribute to the transmission of disease and chains of infection are cut. For example, if a high proportion of a population gets a flu vaccine, the chances of non-immunized people catching the illness also fall.
However, in the story of Covid-19, it’s taken on a slightly different meaning. Since the world does not yet have a viable vaccine, the aim is to allow the controlled spread of the virus through the population. While protection might be provided to the most vulnerable, such as people with weak immune systems, the majority of people are expected to carry on as normal and catch the disease. So the theory goes, many people will be infected but only experience a mild illness. This will allow them to develop antibodies and thereby gain immunity to the disease, eventually meaning much of the population will be immune to the disease, halting its spread.
A handful of European countries have used this approach with varying degrees of severity, but Sweden is the country that’s become most closely tied to the idea, opting for extremely minimal lockdown measures and not mandating the use of face masks in public.
Unfortunately, it didn’t work. Sweden – the poster child of this approach – has seen significantly higher rates of Covid-19 infection, hospitalization, and death compared with neighboring countries. The health authorities in Sweden predicted that just under half of the people in Stockholm would have the disease and acquire antibodies by May 2020. However, the real figure was 15 percent.
The situation is likely to be even worse in the US, with scientists estimating that less than 10 percent of the US population have been infected and gained antibodies. Worst still, researchers are not certain how long a person's antibodies last for Covid-19, meaning there’s no guarantee of long-term immunity after being infected.
Furthermore, defining who is vulnerable and should be protected is complicated. What about young people with diabetes? Obese people? Or smokers? One study estimated that around 30 percent of people in some areas of the world may have some underlying health conditions that would make them vulnerable to Covid-19, so should all of these people be protected or subject to the spread?
Dozens of leading medical and public health experts have recently written a letter in the Lancet medical journal describing this form of herd immunity as a “fallacy unsupported by scientific evidence.”
Even beyond the scientific doubt, it’s a notoriously nasty approach to tackling a disease outbreak. As we’ve seen from Covid-19, it isn’t just the elderly and ill that can fall severely ill with this disease. If the virus is allowed to spread through the population, a considerable number of presumed healthy people will become casualties and fatalities.
Off the back of renewed interest in the idea, the World Health Organization has also recently come to described attempts to reach herd immunity through exposing people to a virus as “scientifically problematic and unethical.”
“Letting Covid-19 spread through populations, of any age or health status will lead to unnecessary infections, suffering, and death,” Dr Tedros Adhanom Ghebreyesus, the WHO Director-General, said at a media briefing on October 12.
“Never in the history of public health has herd immunity been used as a strategy for responding to an outbreak, let alone a pandemic. It is scientifically and ethically problematic,” he added.
This article has been amended to include a video by Yale University about herd immunity and vaccines.