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Herd Immunity Approaches To Control COVID-19 'A Dangerous Fallacy', Say Scientists

The letter, published in The Lancet journal, referred to by its authors as the John Snow Memorandum, noted that any pandemic management strategy relying upon the population to develop immunity from natural infections for COVID-19 is flawed.

Oct 15, 2020 / 12:06 PM IST

Managing COVID-19 by allowing herd immunity to develop in low-risk populations while protecting the most vulnerable is "a dangerous fallacy unsupported by the scientific evidence," warn an international group of 80 researchers in an open letter.

The letter, published in The Lancet journal, referred to by its authors as the John Snow Memorandum, noted that any pandemic management strategy relying upon the population to develop immunity from natural infections for COVID-19 is flawed.

In the face of a second wave of infection in several parts of the world, the scientists including Devi Sridhar from the University of Edinburgh in the UK, said there is currently renewed interest in herd immunity approaches allowing a large uncontrolled outbreak in low-risk populations while protecting the vulnerable.

While some have argued this approach could lead to the development of infection-acquired immunity in the low-risk population, which will eventually protect the vulnerable, the researchers explained such uncontrolled transmission in younger people risks significant ill-health and death.

Based on evidence from many countries, the scientists said it is not possible to restrict uncontrolled outbreaks to certain sections of society, adding that it is "practically impossible" and "highly unethical" to isolate large swathes of the population.

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COVID-19 Vaccine

Frequently Asked Questions

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How does a vaccine work?

A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.

How many types of vaccines are there?

There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.

What does it take to develop a vaccine of this kind?

Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.

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While special efforts to protect the most vulnerable are essential, they said these must go hand-in-hand with multi-pronged population-level strategies.

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"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," they wrote in the letter.

"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 researchers said.

According to the scientists, the restrictions can effectively suppress the number if infections to low levels that allow rapid detection of localised outbreaks.

They said such measures can also compliment rapid response through efficient and comprehensive testing, contact tracing, isolation and support systems.

"Protecting our economies is inextricably tied to controlling COVID-19. We must protect our workforce and avoid long-term uncertainty," they said.

The researchers cautioned that there is currently no evidence for lasting protective immunity to SARS-CoV-2 after natural infection.

They said 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.

According to the scientists, vulnerable populations are 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.

So they called for controlling the spread of the virus until the population can be vaccinated.

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, the researchers warned.

They said clinicians still do not understand who might suffer from 'long COVID' in which the symptoms linger for weeks.

"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," the scientists wrote.

"We cannot afford distractions that undermine an effective response; it is essential that we act urgently based on the evidence," they concluded.

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PTI
first published: Oct 15, 2020 12:06 pm

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