Is herd immunity a feasible strategy against COVID-19?

Without a clear understanding of the multiplicative processes of a disease during a pandemic, global lawmakers resorted to mindfulness rather than taking the risks connected to the ‘herd-immunity’ argument. This term describes the wish to protect an individual by reaching immunity for a significant part of the population. Due to this immunity, individuals are supposedly shielded from becoming infected with a disease. Given there is vaccination, immunity is achieved via mostly direct means, as contagious people may still infect others. Another form of it, however, as in the case of COVID-19, is the attempt to understand infection and death rate of a novel disease, and to subsequently allow it to spread amongst a population in order to achieve indirect protection for the individual.

The assumption that herd immunity is desirable is based on 1) the wish to provide immunity and thus safety faster than having to pass through the formal process of the creation of a vaccine, and 2) the hope to protect economic activity by avoiding the enforcement of isolation measures, effective until suspended by authorities.

The United Kingdom and the Netherlands were early and vocal advocates of said strategy. While the Netherlands went beyond the UK and eventually implemented what they phrased “intelligent lockdown” – arguing that the elderly were sufficiently protected by staying home while the young are able to conduct business as usual –, the UK changed course and closed everything non-essential after mathematical researchers showed that herd immunity could claim a quarter of a million lives due to its possible exponential growth.

What is upsetting is not only the calculated acceptance of death for those with weak immune systems, such as the elderly or persons with prior health conditions, but also ‘higher-order’ consequences that stem from these deaths, e.g. the loss of responsibility that those people carried and bad future decision-making. Additionally, a vast number of newly-ill would fully overwhelm hospitals and other national health services, and therefore exacerbate the conditions for those with other diseases, showing negative reciprocity of these consequences.

Two crucial aspects early in this decision-making chain are severely problematic: one being the immorality of the cost-effectiveness approach, where death (especially of the elderly) is seen as a necessary evil to get the desired outcome, i.e. protection for the individual.

The second aspect is the pretentiousness of scientific conduct by claiming the UK could only implement isolation measures after having gathered enough evidence for their necessity, which in light of the potential fatal consequences is irresponsible. This ‘evidence-based approach’ was argued for under the pretence of science up until mid-March in the UK by Patrick Vallance, scientific adviser to the Government since 2018.

Stanford University’s John Ioannidis, currently the most cited epidemiologist in the world (in April of 2020 267,437 citations), is delivering claims in support of herd immunity. Professor Ioannidis argues that the mathematical modelling of exponential growth is prone to sometimes drastically differing results between model and reality. “If you make a small mistake in the base numbers, you end up with a final number that could be off 10-fold, 30-fold, even 50-fold”.

Despite sounding as if he offered a sound argumentation in favour of the precautionary principle, he concludes the possibility of an overestimation of bad real-world outcomes. However, intuition rather dictates to be prepared for the opposite: If there is the possibility for model error, and if scientists are uncertain about the error rate – especially when dealing with exponential growth, then it appears reasonable not to hope the model’s error rate is favourable but rather that it worsens bad outcomes, as Professor Nassim N. Taleb vehemently advocates.

Edited by: Patrick Lehner