Herd immunity a ‘dangerous fallacy’ according to researchers

Herd immunity a ‘dangerous fallacy’ according to researchers
iStock-Lyubov Ivanova

Herd immunity is a ‘dangerous fallacy’ according to 80 researchers who have penned an open letter published in The Lancet.

The researchers warn that a so-called herd immunity approach to managing COVID-19 – by allowing immunity to develop in low-risk populations while protecting the most vulnerable – is ‘a dangerous fallacy unsupported by the scientific evidence’.

Faced with a second wave of COVID-19, and more than a million recorded deaths worldwide, the authors present their view of the scientific consensus on our understanding of COVID-19, and the strategies that need to be put in place to protect societies and economies.

Relying on herd immunity is flawed

Referred to by its authors as the John Snow Memorandum, the open letter, which will also be launched during the 16th World Congress on Public Health programme 2020, is signed by 80 international researchers (as of publication) with expertise spanning public health, epidemiology, medicine, paediatrics, sociology, virology, infectious disease, health systems, psychology, psychiatry, health policy, and mathematical modelling.

The authors of the letter state: ‘It is critical to act decisively and urgently. Effective measures that suppress and control transmission need to be implemented widely, and they must be supported by financial and social programmes that encourage community responses and address the inequities that have been amplified by the pandemic.

‘Continuing restrictions will probably be required in the short term, to reduce transmission and fix ineffective pandemic response systems, in order to prevent future lockdowns. The purpose of these restrictions is to effectively suppress SARS-CoV-2 infections to low levels that allow rapid detection of localised outbreaks and rapid response through efficient and comprehensive find, test, trace, isolate, and support systems so life can return to near-normal without the need for generalised restrictions. Protecting our economies is inextricably tied to controlling COVID-19. We must protect our workforce and avoid long-term uncertainty.’

The authors acknowledge that ongoing restrictions have understandably led to widespread demoralisation and diminishing trust among the public, and that in the face of a second wave of infection there is renewed interest in so-called natural herd immunity approaches, and say that any pandemic management strategy relying upon immunity from natural infections for COVID-19 is flawed.

Transmission in young people risks the whole population

Uncontrolled transmission in younger people risks significant ill-health and death across the whole population, the authors explain, as real-world evidence from many countries demonstrates that it is not possible to restrict uncontrolled outbreaks to certain sections of society, and it being practically impossible and highly unethical to isolate large swathes of the population. Instead, the authors say that special efforts to protect the most vulnerable are essential but must go hand-in-hand with multi-pronged population-level strategies.

Vaccinating the population

According to the letter, there is also no evidence for lasting protective immunity to COVID-19 after natural infection, and warn that this waning immunity as a result of natural infection would not end the COVID-19 pandemic but instead result in repeated waves of transmission over several years.

This could place vulnerable populations at risk for the indefinite future, as natural infection-based herd immunity strategies would result in recurrent epidemics, as seen with many infectious diseases before mass vaccination. Instead, the authors call for suppression of the virus until the population can be vaccinated.

They also warn that natural infection-based herd immunity approaches risk impacting the workforce as a whole and overwhelming the ability of healthcare systems to provide acute and routine care, noting that we still do not understand who might suffer from ‘long COVID’, and that herd immunity approaches place an unacceptable burden on healthcare workers, many of whom have died from COVID-19 or experienced trauma as a result of having to practice disaster medicine.

The letter concludes: ‘The evidence is very clear: controlling community spread of COVID-19 is the best way to protect our societies and economies until safe and effective vaccines and therapeutics arrive within the coming months. We cannot afford distractions that undermine an effective response; it is essential that we act urgently based on the evidence.’


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