The problem with trying to achieve herd immunity
As the global struggle to contain COVID-19 continues, and pandemic fatigue sets in, some are advocating for a socalled natural “herd immunity” strategy, which they argue can be safely achieved through “focused protection.”
This concept entails fully reopening societies, while “shielding” the elderly and people with co-morbidities, in order to achieve herd immunity in the absence of a vaccine within six months.
It sounds so simple, but the facts tell us otherwise.
First, herd immunity is achieved by protecting people from a virus with the use of a vaccine, not by exposing them to it.
For example, herd immunity against measles requires about 95 per cent of people to be vaccinated. Once immunized against measles, they act as a protective buffer preventing the virus from circulating and infecting the remaining 5 per cent of the population who are unvaccinated.
Second, we are nowhere close to the levels of immunity required to stop this disease transmitting. We know that less than 10 per cent of the global population has shown evidence of infection. To achieve herd immunity for SARSCoV-2, it is estimated that at least 60 to 70 per cent of the global population — more than five billion people — would need to be infected which, in the absence of a vaccine, may take years.
Furthermore, as with other coronaviruses, reinfection cannot be ruled out, exposing people to disease again and again. Cases of reinfection have already been reported.
Third, letting the virus spread through populations unchecked would have devastating consequences for communities and health systems. Far too many people would develop severe disease and die, hospitals would be overwhelmed with the influx of patients, particularly as flu season takes off in the northern hemisphere, and communities would be ravaged by the sheer number of people in need of care.
We also have no idea how many people will suffer the debilitating effects of post-COVID syndrome or “Long COVID,” or for how long. Many people describe suffering from months of persistent fatigue, headaches, “brain fog” and trouble breathing.
Other serious conditions from being sick with COVID -19 — such as physical and cognitive limitations, psychiatric problems and issues with the lungs, heart and brain — are being reported.
Fourth, it is a mistake to believe that the virus only severely affects older people and those with underlying conditions. Many young people with no underlying health conditions have developed severe disease and died.
At the peak of Italy’s outbreak, up to 15 per cent of all people in intensive care were under 50.
Finally, how would this theoretical “focused protection” play out in the real world? Governments are already encouraged to protect high-risk groups. Choosing a single intervention, with disregard for the realities of local transmission, would be unwise, ineffective and deadly.
Rather than wasting precious resources discriminating against high-risk groups, we should focus on going after the virus.
Through robust testing and contact tracing, we can know precisely where the virus is circulating, and clamp down on it with the tried and tested public health measures.
By tailoring interventions to local contexts and targeting disease clusters, we can avoid punishing national lockdowns that are blind to variations in community transmission.
By informing individuals about how they might protect themselves and their loved ones, we can reduce the disease burden. We’ve seen this approach succeed in many countries. It is hard work, but we have new and better tools than we did nine months ago.
There are currently more than 200 vaccine candidates, with several in the final stage of clinical trials. We could have limited supplies of an efficacious SARS-CoV2 vaccine available as early as next year. When that happens, we can realistically and safely strive for herd immunity.
Until then, we have to outsmart this virus, by understanding where and how it spreads, and not giving it a chance to do so.
To achieve herd immunity for SARS-CoV-2, it is estimated that more than five billion people would need to be infected