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article imageOp-Ed: A herd immunity policy? The risks remain considerable

By Tim Sandle     Oct 12, 2020 in Health
As part of the efforts to combat coronavirus discussion around ‘herd immunity’ periodically arises. What does this mean exactly and why is the majority of scientific and political opinion against such a strategy?
The question of whether governments should consider the mass population developing herd immunity in order to combat the coronavirus has been an on-and-off topic throughout the pandemic. Herd immunity refers to a point in time when a large portion of a community (theso-called 'herd') becomes immune to a disease. At this point, the further spread of disease from person to person becoms very unlikely. Around 94 percent of the population needs to become immune to interrupt the chain of transmission. Hitting this target requires the infection (and death) rate to rise.
Advocates for herd immunity raise the point that the practice returns ‘freedoms’ to the majority of the population and it is of economic benefit. Some extreme adovactes even tak about an acceptable level of death from the SARS-CoV-2 virus.
Those against herd immunity cite models that indicate an unacceptable pattern of deaths. For example, Imperial College London, looking at the U.K. as a whole, predicted a further death toll of 250,000 if Boris Johnson’s government was to embark on such a strategy. So far this is a risk that the U.K. government, together with most world governments, has not been prepared to take.
It also remains that it is unclear whether herd immunity would work, especially in the context of social distancing requirements. This has led to discussions around the impracticalities of herd immunity strategies. On the other hand, if it did start to work how such a practice could be phased so it does not overwhelm a national healthcare system is uncertain, especially in the context of uncertainty over how long the whole process might take.
Scientists at the University of Georgia have been running models to try to answer the time questions. Their paper is published in PNAS, titled "Transmission dynamics reveal the impracticality of COVID-19 herd immunity strategies." The study involved looking at two separate approaches, which they term “suppression” and “mitigation”.
Suppression is the means to “suppress transmission in the target population,” by using strict controls, for a prolonged period, such as closing offices and schools and enforcing strong social distancing measures.
Mitigation is an attempt to manage the health impacts of the pandemic by preventing the country’s healthcare system from being overwhelmed. This sinvolves reducing, but not halting, transmission and localizing it to a less at-risk population.
The researchers found that the only way to achieve herd immunity is to divide the population into over-60s, who need to isolate,and the under-60s, who are allowed to mix on a controlled and phased basis. The predicted time taken to achieve herd immunity would be around 12 months, under the model described. Whether any one aged over-60 would want to self-isolate for at least one year is unlikely.
This best case model continues to show that herd immunity is impractical, if it works at all. Herd immunity can occur naturally with some specific diseases. Whether governments can bend forces of nature (as the coronavirus is) to behave in a certain way is unclear, as is the potential for human populations to go along with any such attempts.
This opinion article was written by an independent writer. The opinions and views expressed herein are those of the author and are not necessarily intended to reflect those of
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