Covid-19: “Herd immunity is a dangerous fallacy without scientific support” | Science


The so-called herd immunity, which consists of allowing the population to become freely infected so that they can develop protection naturally, is “a dangerous fallacy without scientific evidence”. In this striking way, a group of 80 scientists expressed themselves in an open letter published in the medical journal The Lancet, in response to the proliferation of theories that defend this strategy against the coronavirus. The researchers warn that the absence of control measures would increase mortality in the entire population, affect the economy irreversibly, prolong the epidemic and paralyze all health systems. The scientific director of the World Health Organization (WHO), Soumya Swaminathan, estimates that 1% of the world population (77 million people) would die with a measure like natural collective immunization.

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In September, a preliminary scientific study found that 66% of Manaus residents, in the heart of the Amazon rainforest, already had antibodies to covid-19, which would make the city the first in the world to achieve collective immunity. This would be the product of the simple inaction of the government to contain the advance of the pandemic. The research still needs to go through peer review, however, a new wave of cases in the region calls this thesis into question.

The strategy of allowing free infection among people, however, did not start in Brazil. It gained momentum after a proposal, called the Great Barrington Declaration, signed by epidemiologists Martin Kulldorff (from Harvard University), Sunetra Gupta (Oxford) and Jay Bhattacharya (Stanford). His idea is “to allow those who are at minimal risk of death to live their lives normally to achieve immunity to the virus through natural infection, while better protecting those who are at greatest risk,” according to the three signatories. “We call this Focused Protection.”

The proposal generated numerous adhesions, but also the immediate reaction of WHO and the scientific community, which ended up responding through the 80 signatories of the letter in the The Lancet and where they note, at the outset, that “the proportion of vulnerable people constitutes up to 30% of the population in some regions”.

“Any pandemic management strategy that depends on the immunity from natural coronavirus infections is erroneous,” say the scientists. According to them, uncontrolled transmission in younger people (supposedly at lower risk of death) may end up increasing mortality in the entire population. “The human cost would be huge,” adds Swaminathan.

The WHO scientific director also points out that achieving collective immunity in a natural way would require that at least 70% of the population develop antibodies, a process that would take a long time and that the authors of the open letter warn that it would have catastrophic effects on the economy global. “In addition, there is no evidence of a lasting protective immunity to SARS-CoV-2 as a result of natural infection, and endemic transmission would pose a risk to vulnerable populations,” they add.

In addition to high mortality, the herd immunity strategy would pose an unsustainable challenge for health systems. “If everybody gets sick at once, the hospital system has to be very well designed to be able to absorb all these patients”, write Esperanza Gómez-Lucía and José Antonio Ruiz-Santa-Quiteria, researchers at the Department of Animal Health at the Complutense University of Madrid.

Farming immunity, far from putting an end to the pandemic, according to the scientists, “would give rise to recurrent epidemics, as occurred with numerous infectious diseases before the development of vaccines”. This is the case of the resurgence of measles where anti-vaccine movements have proliferated or immunization programs have not been completed.

The letter’s authors are also against the concept of Focused Protection, defended by the authors of the Great Barrington Declaration. Firstly, because defining who is vulnerable is complex in the case of the coronavirus and, secondly, because they claim that “prolonged isolation of large sections of the population is practically impossible and unethical”.

“The empirical evidence from many countries shows that it is not feasible to restrict uncontrolled outbreaks to particular sectors of society. This approach also runs the risk of further exacerbating the socioeconomic inequalities and structural discrimination already exposed by the pandemic ”, argue the scientists.

WHO Director-General Tedros Adhanom added to these warnings and said that collective immunity means “allowing infections, suffering and unnecessary deaths”. “Never in the history of public health has collective immunity been used as a strategy to respond to an outbreak, let alone a pandemic. It is scientifically and ethically questionable, ”he said.

Adhanom and the scientists attribute the adherences to the questioned group immunity to “the frustration that the advance of the pandemic raises in many people, communities and Governments”. But he insists that the only way to obtain collective immunity is through vaccines. “There is no shortcut or single measure. You have to use all the tools that we have. ”

The coronavirus has already infected more than 35 million people worldwide and caused the death of more than one million. Scientists point out that the only effective measures are those that suppress and control transmission, supported by financial and social programs.

The concrete measures they advocate coincide with those globally accepted: physical distance, use of facial coatings, respiratory and hand hygiene, avoiding crowds and poorly ventilated spaces, rapid tests, contact tracking and isolation. These are essential to reduce mortality and prevent the collapse of health services.

“The evidence is very clear: controlling the community’s spread of covid-19 is the best way to protect our societies and economies until safe and effective vaccines and therapies arrive in the coming months. We cannot afford distractions that undermine an effective response; it is essential to act urgently on the basis of evidence ”, conclude the researchers.

The group of 80 international scientists who sign the letter in The Lancet it is composed of researchers in public health, epidemiology, medicine, pediatrics, sociology, virology, infectious diseases, health systems, psychology, psychiatry, health policy and mathematical modeling. The letter will be officially launched during the 16th World Congress on Public Health.


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