Public health measures aiming to achieve ‘herd immunity’ are criticised by a multidisciplinary group of researchers who call it "a dangerous fallacy unsupported by the scientific evidence".


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In the John Snow Memorandum, an open letter published in The Lancet and presented during the 16th World Congress on Public Health, an international group of 80 (as of publication) researchers summarise the current understanding of COVID-19 and outline strategies that, in their opinion, would be the most efficient in protecting both the public health and the economy. The authors come from a variety of fields including infectious disease, epidemiology, sociology, virology, public health, health systems, etc.


In the face of approaching winter and the second wave that is affecting Europe, the authors call for “clear communication about the risks posed by COVID-19 and effective strategies to combat them”.


The virus, which has already infected over 35 million people globally and led to more than 1 million deaths, is highly infectious on both short and longer distances creating conditions for rapid community spread. The fatality rate is much higher than that of influenza, and the severity of illness may be high even in low-risk groups. Furthermore, neither the immunity period nor the frequency of reinfection are yet known.


It is proven that measures like physical distancing, mask wearing and basic hygiene help to mitigate the spread, especially when combined with testing, contact tracing and isolation policies. While the lockdowns, which were introduced by many countries in the beginning of the pandemic, have negatively affected people’s physical and mental health and disrupted the economy, they have given the necessary time to establish effective pandemic control systems at least in some countries. Still, “this has understandably led to widespread demoralisation and diminishing trust,” the authors note.


As a result, currently the idea of a so-called ‘herd immunity,’ i.e. allowing uncontrolled infections in low-risk groups of population while protecting the vulnerable, is gaining popularity as a less extreme alternative to lockdowns. The authors call this approach “a fallacy”. They argue that “any pandemic management strategy relying upon immunity from natural infections for COVID-19 is flawed”. Uncontrolled outbreaks pose a risk of high morbidity and mortality in populations, they point out, and would inevitably have a negative impact on the state of the economy and healthcare systems.


This is further exacerbated by the lack of evidence that COVID-19 immunity lasts long enough to support the ‘herd immunity’ strategies, stretching the risk for vulnerable groups into “the indefinite future” and burdening the economy. “Prolonged isolation of large swathes of the population is practically impossible and highly unethical,” the authors write. “Empirical evidence from many countries shows that it is not feasible to restrict uncontrolled outbreaks to particular sections of society.” They argue that while protecting the most vulnerable is essential, it must be supported with multidimensional population-level strategies aimed at both the society and the economy. Japan, Vietnam and New Zealand are cited as examples of countries where robust public health responses have helped to contain the pandemic and allowed the “near-normal” continuation of life.


In conclusion the authors urge focussing on controlling community spread of COVID-19 before effective vaccines and treatments are available, and call their colleagues to sign the Memorandum.


Source: The Lancet

Image credit: Feodora Chiosea via iStock


Alwan NA et al. (2020) Scientific consensus on the COVID-19 pandemic: we need to act now. The Lancet, published: 15 October.

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public health, COVID-19, mitigation measures, herd immunity, pandemic prevention COVID-19: Immunity-Based Strategies are ‘Flawed’