There is much talked about so-called herd immunity. Many people are under the impression that by 'letting the virus rip' the general population would get the virus, people would become immune and life could return to normal. But this fails to understand the science.
Herd immunity
Herd immunity occurs when a virus is allowed to spread freely and thus many people would become immune. However, at least 60-70% of any one population would need to become immune in order for such a strategy to work. In a country of some 100 million people this could mean around 1.8 million people dying given the currently estimated fatality rate of around 3%. This also does not take into account those that would become seriously ill and not die, further stretching national health resources.
Herd immunity occurs when a virus is allowed to spread freely and thus many people would become immune. However, at least 60-70% of any one population would need to become immune in order for such a strategy to work. In a country of some 100 million people this could mean around 1.8 million people dying given the currently estimated fatality rate of around 3%. This also does not take into account those that would become seriously ill and not die, further stretching national health resources.
[Concerning the death rate from COVID-19, it is very difficult to evaluate given low testing rates. Initial statistics from New York appeared to indicate a massive 8% fatality rate [Atlantic]. However, as the numbers of tests increase and are measured against death rates statistic appear to show fatality is more likely between 1-3%]
Globally, the numbers would be many times higher. The head of the World Health Organization worries a herd immunity approach could lead to more problems.
"Allowing a dangerous virus that we don't fully understand to run free is simply unethical," according to Tedros Adhanom Ghebreyesus, the World Health Organization's director-general. "It's not an option."
Dr. Anthony Fauci agrees. "There will be so many people in the community that you can't shelter, that you can't protect, who are going to get sick and get serious consequences," the director of the National Institute of Allergy and Infectious Diseases said. "So, this idea that we have the power to protect the vulnerable is total nonsense."
Even if this death rate were to be acceptable in order to 'return society to normal' there are still many unknowns concerning the COVID-19 coronavirus. It remains uncertain how long immunity lasts once you get coronavirus. Indeed there are at least two documented cases of reinfection, one in Hong Kong and another in the US. There is also the possibility that COVID-19 could mutate, making immunity to the current strain meaningless with regards to the contracting of a mutated version of the virus [Al Jazeera].
Globally, the numbers would be many times higher. The head of the World Health Organization worries a herd immunity approach could lead to more problems.
"Allowing a dangerous virus that we don't fully understand to run free is simply unethical," according to Tedros Adhanom Ghebreyesus, the World Health Organization's director-general. "It's not an option."
Dr. Anthony Fauci agrees. "There will be so many people in the community that you can't shelter, that you can't protect, who are going to get sick and get serious consequences," the director of the National Institute of Allergy and Infectious Diseases said. "So, this idea that we have the power to protect the vulnerable is total nonsense."
Even if this death rate were to be acceptable in order to 'return society to normal' there are still many unknowns concerning the COVID-19 coronavirus. It remains uncertain how long immunity lasts once you get coronavirus. Indeed there are at least two documented cases of reinfection, one in Hong Kong and another in the US. There is also the possibility that COVID-19 could mutate, making immunity to the current strain meaningless with regards to the contracting of a mutated version of the virus [Al Jazeera].
A safe vaccine is only route out
A safe and effective COVID-19 vaccine is the only safe way out of the COVID-19 coronavirus pandemic, though any mutation in the virus itself could nullify the effort to immunise a population to some extent. That said, a vaccine for COVID-19 is still the best route though further vaccines may need to be developed should the virus mutate significantly.
Of course even with rates of vaccination above 93%, herd immunity offers no guarantees. Relocation, travel or even a new circle of friends can change the composition of one's herd, and thus its shared protection against infection. Therefore, any COVID-19 vaccine needs to be rolled out globally [Global Health Now-John Hopkins].
The measles vaccine has not only prevented deaths and other long-term effects of the disease but also prevented 'immune amnesia' whereby the body's immune system forgets immunity to other diseases [Harvard].
Low seroprevalence of COVID-19
As regards the COVID-19 coronavirus herd immunity is unlikely to work. Studies in June and July 2020 cast doubt on prospects for herd immunity. Despite months of exposure, antibody surveys found a low seroprevalence, less than 10%, in cities in Spain and Switzerland. Commentators in The Lancet concluded that "In light of these findings, any proposed approach to achieve herd immunity through natural infection is not only highly unethical, but also unachievable" [Lancet].
Seroprevalence is the number of persons in a population who test positive for a specific disease based on serology specimens; often presented as a percent of the total specimens tested or as a proportion per 100,000 persons tested. However, as an article published by the BMJ in September highlights, the seroprevalence of SARS-CoV-2 may be underestimated. Indeed current seroprevalence studies may fail to detect people who have had mild COVID-19. In addition due to the fact that antibody tests have not been widely deployed - often reserved for key workers in the health industry - those that missed the boat for regular coronavirus testing, and who perhaps even had relatively serious symptoms but who were not hospitalised, have not been added to the figures.
So estimations as to the numbers that have had the coronavirus within many populations are simply that; estimations. That said, it is still not clear whether contracting and recovery from the COVID-19 coronavirus produces long-term immunity.
No guaranteed immunity
In the first such case documented by a team of researchers at the University of Hong Kong a man was shown to have contracted the virus for a second time. The man, a 33-year-old IT worker, recovered from coronavirus and was released from hospital in April. However, he again tested positive for the virus when he returned from Spain early in August [AA / CNN].
Meanwhile in Nevada in the United States another man was reported to have contracted the virus twice, the first time in April and subsequently in May [BBC].
While such cases appear to be isolated, they do raise questions concerning long term immunity. "Our findings signal that a previous infection may not necessarily protect against future infection," said Dr Mark Pandori, from the University of Nevada.
So far, reinfection seems to be rare - there have been only a few examples out of more than 37 million confirmed cases globally.
Reports from Hong Kong, Belgium and the Netherlands suggest they were no more serious than the first. One in Ecuador mirrored the US case in being more severe, but did not need hospital treatment.
However, it is still early into the pandemic, and the history of other types of coronavirus means protection is expected to wane.
Letting virus rip would be a disaster
What seems clear is that 'letting the virus rip' would bring with it countless deaths while likely collapsing the health service and overstretching services dealing with the disposal of bodies.
A safe and effective COVID-19 vaccine is the only safe way out of the COVID-19 coronavirus pandemic, though any mutation in the virus itself could nullify the effort to immunise a population to some extent. That said, a vaccine for COVID-19 is still the best route though further vaccines may need to be developed should the virus mutate significantly.
Of course even with rates of vaccination above 93%, herd immunity offers no guarantees. Relocation, travel or even a new circle of friends can change the composition of one's herd, and thus its shared protection against infection. Therefore, any COVID-19 vaccine needs to be rolled out globally [Global Health Now-John Hopkins].
The measles vaccine has not only prevented deaths and other long-term effects of the disease but also prevented 'immune amnesia' whereby the body's immune system forgets immunity to other diseases [Harvard].
Low seroprevalence of COVID-19
As regards the COVID-19 coronavirus herd immunity is unlikely to work. Studies in June and July 2020 cast doubt on prospects for herd immunity. Despite months of exposure, antibody surveys found a low seroprevalence, less than 10%, in cities in Spain and Switzerland. Commentators in The Lancet concluded that "In light of these findings, any proposed approach to achieve herd immunity through natural infection is not only highly unethical, but also unachievable" [Lancet].
Seroprevalence is the number of persons in a population who test positive for a specific disease based on serology specimens; often presented as a percent of the total specimens tested or as a proportion per 100,000 persons tested. However, as an article published by the BMJ in September highlights, the seroprevalence of SARS-CoV-2 may be underestimated. Indeed current seroprevalence studies may fail to detect people who have had mild COVID-19. In addition due to the fact that antibody tests have not been widely deployed - often reserved for key workers in the health industry - those that missed the boat for regular coronavirus testing, and who perhaps even had relatively serious symptoms but who were not hospitalised, have not been added to the figures.
So estimations as to the numbers that have had the coronavirus within many populations are simply that; estimations. That said, it is still not clear whether contracting and recovery from the COVID-19 coronavirus produces long-term immunity.
No guaranteed immunity
In the first such case documented by a team of researchers at the University of Hong Kong a man was shown to have contracted the virus for a second time. The man, a 33-year-old IT worker, recovered from coronavirus and was released from hospital in April. However, he again tested positive for the virus when he returned from Spain early in August [AA / CNN].
Meanwhile in Nevada in the United States another man was reported to have contracted the virus twice, the first time in April and subsequently in May [BBC].
While such cases appear to be isolated, they do raise questions concerning long term immunity. "Our findings signal that a previous infection may not necessarily protect against future infection," said Dr Mark Pandori, from the University of Nevada.
So far, reinfection seems to be rare - there have been only a few examples out of more than 37 million confirmed cases globally.
Reports from Hong Kong, Belgium and the Netherlands suggest they were no more serious than the first. One in Ecuador mirrored the US case in being more severe, but did not need hospital treatment.
However, it is still early into the pandemic, and the history of other types of coronavirus means protection is expected to wane.
Letting virus rip would be a disaster
What seems clear is that 'letting the virus rip' would bring with it countless deaths while likely collapsing the health service and overstretching services dealing with the disposal of bodies.
Lockdowns are certainly expensive to the economy. But if strictly enforced and planned properly with a proper escape plan of widespread testing, track & trace, hygiene and social distancing measures, lockdowns work.
Countries that have done the best, New Zealand, Taiwan, Iceland, Singapore and South Korea - to name a few - imposed swift travel bans with testing and quarantining for arrivals, implemented track & trace, and imposed swift lockdowns on identified outbreaks. Clear messaging has also played a part for countries that have slowed the spread, including the advice concerning masks the efficacy of which was dismissed by many countries that have done particularly badly.
There will be no quick way out of the pandemic, but what is clear that letting the virus go is not the correct route.
[CNN - herd immunity / WBRC - herd immunity / Kurzgesagt-COVID-19 / Kurzgesagt-Vaccines Explained].
[CNN - herd immunity / WBRC - herd immunity / Kurzgesagt-COVID-19 / Kurzgesagt-Vaccines Explained].
tvnewswatch, London, UK
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