Table of contents:
- Childhood virus
- Vaccines and herd immunity
- Does it look like the flu?
- Measles-like virus
- Animals as reservoirs of the causative agent of infection
Video: Can covid-19 be completely eradicated?
2023 Author: Seth Attwood | [email protected]. Last modified: 2023-11-26 22:42
Can vaccination be counted on as a means to completely eradicate covid-19? According to scientists, this virus is with us forever. Another question is how he will behave in the future. Perhaps covid-19 will become endemic and resemble "something like the flu." But we must not forget about its ability to deceive the immune system.
An article from the journal Nature claims that many scientists believe the virus that causes covid-19 will become endemic. Over time, its danger to humans may decrease.
Western Australia was largely free of any coronavirus last year. In pubs, as usual, friendly companies continued to gather, lovers kissed, relatives hugged, children went to school without masks, no one measured their temperature. And this atmosphere was preserved there only thanks to the introduction of severe travel restrictions and thanks to quarantine - in some regions it had to be urgently introduced at the beginning of the year after one of the hotel's security officers, whose visitors were in quarantine, did not pass the coronavirus test.
But the experience of Western Australia has shown us: this is what a life free from the SARS-CoV-2 coronavirus means. And if other regions try to use vaccination to reduce the incidence of covid to zero, then can humanity hope that the coronavirus will be completely destroyed in this case?
Sounds optimistic. However, most scientists consider all these dreams to be unrealistic. In January of this year, the journal Nature interviewed more than 100 immunologists, infectious disease specialists and specialists studying the coronavirus, asking them the question: is it possible to completely eradicate this very coronavirus? Almost 90% of respondents answered that the coronavirus will become endemic, which means that it will continue to spread among different populations around the world for many years.
“Trying to eradicate this virus right now and in all regions of the world is somewhat like trying to build a bridge to the moon. This is unrealistic,”says epidemiologist Michael Osterholm of the University of Minnesota in Minneapolis.
But our inability to completely deal with the virus does not mean that mortality, morbidity, social isolation will continue to remain at the same level. The future largely depends on the immunity that humans acquire as a result of infection or vaccination, as well as on the evolution of the coronavirus itself.
Recall that the flu virus and the other four coronaviruses that cause the common cold in humans are also endemic; however, annual vaccinations, coupled with acquired immunity, mean that the human population will have to face seasonal mortality and disease, but without quarantine, without wearing masks and without social distancing.
More than a third of respondents surveyed by Nature say the SARS-CoV-2 coronavirus can be eradicated in some regions but will continue to spread in others. Regions with zero covid levels will have a high likelihood of new outbreaks of viral diseases, but they will be quickly suppressed thanks to herd immunity, provided that the majority of local residents are vaccinated. “I assume that covid will be eliminated in some countries.
However, there will be a (possibly seasonal) decrease in the likelihood of re-exposure of the current coronavirus from regions where vaccination coverage and public health measures are inadequate,”says epidemiologist Christopher Dye of the University of Oxford. Great Britain.
“The coronavirus is likely to become endemic, but how will it mutate? It's hard to predict,”said virologist Angela Rasmussen of Georgetown University in Seattle, Washington.
Thus, the emergence of the SARS-CoV-2 coronavirus inevitably leads to the emergence of social costs in the next five, ten or even fifty years.
In five years, the covid-19 pandemic will most likely be forgotten. And so, when the management of a kindergarten informs the parents that their child has a runny nose and a high fever, it is quite possible that the culprit of these ailments will be the familiar coronavirus - the same one that claimed more than one and a half million people in 2020 alone.
This, according to scientists, is another scenario for the evolution of the SARS-CoV-2 coronavirus. This coronavirus will persist, but as soon as people develop immunity to it - whether it happens as a result of natural infection or as a result of vaccination - severe symptoms will no longer appear.
According to infectious disease researcher Jennie Lavine of Emory University in Atlanta, Georgia, the coronavirus will become the very enemy that people will first encounter in early childhood; it, as a rule, will cause an infectious infection in a mild form, if not at all without any symptoms.
Scientists believe such a scenario is quite possible, since this is how four endemic coronaviruses behave - OC43, 229E, NL63 and HKU1. At least three of these have probably circulated for hundreds of years in the human population; two of these account for approximately 15% of respiratory infections. Summarizing the data from previous studies, Jenny Lavigne, together with colleagues, developed a mathematical model that describes the process of primary infection with the aforementioned coronaviruses in children under the age of six, as well as the development of immunity.
According to Lavigne, this immune defense weakens rather quickly, so it cannot completely prevent re-infection; at the same time, it seems to be able to protect adults from these diseases. Note that even in children, these diseases are relatively mild for the first time.
It is unclear whether immunity to the SARS-CoV-2 coronavirus will act in a similar way. As shown in a representative survey of people who have had covid-19, the concentration of antibodies that prevent re-infection begins to decline after about six to eight months.
But the body of these patients, according to one of the study co-authors, immunologist Daniela Weiskopf of the La Jolla Institute of Immunology in California, also produces B-lymphocytes, which are capable of producing antibodies in case of repeated infection of the body, and T-lymphocytes. which can destroy cells infected with the virus. Scientists have to determine if this immune memory can prevent re-infection with coronavirus; reinfection cases also occur, and due to the emergence of new types of viruses, the likelihood of such infection increases. However, reinfection cases are still considered rare.
Currently, a team of scientists led by Daniela Weisskopf continues to study the immune memory of the human population infected with covid-19; in the course of the study, it is necessary to establish whether the immune memory is preserved or not. As Weisskopf notes, if most people acquire lifelong immunity to coronavirus as a result of natural infection or vaccination, then the coronavirus is unlikely to become endemic.
But immunity may weaken in a year or two - and there is already evidence that the coronavirus is capable of evolving, i.e. he is able to bypass the immune defenses. More than half of the scientists surveyed by the journal Nature believe that weakening of the immune system will be one of the main factors contributing to the spread of the virus.
As the virus has spread throughout the world, it may seem like it can already be categorized as endemic. But, as the infection continues to spread globally and the threat of infection looms over many people, scientists still continue to classify it as one of the phases of a pandemic. During the endemic phase, explains Jenny Lavigne, the number of infections will remain somewhat constant over the years, resulting in occasional outbreaks of the disease.
This steady state could take several years or even decades to reach this steady state, Lavigne said, depending on how quickly the herd immunity develops in the population. If we allow the coronavirus to spread uncontrollably, then, of course, we will reach the aforementioned steady state quickly, however, at the same time, millions of people will die. “We have to face huge costs here,” adds Jenny Lavigne. So, the most optimal way is vaccination.
Vaccines and herd immunity
Countries that use covid-19 vaccines are expected to see a decline in severe cases soon. But it will take longer for specialists to determine how effective vaccines are at preventing transmission. Clinical trial data have shown that vaccines that prevent symptomatic infection can also stop person-to-person transmission of the virus.
If the vaccine really prevents the transmission of the coronavirus (and if the vaccines are also effective against new modifications of the virus), then in those regions where a large enough part of the population has been vaccinated, it may be possible to get rid of the coronavirus; such vaccination will promote the development of herd immunity, which will protect the part of the population that has not been reached by vaccination.
As shown by a mathematical model developed by a group of scientists led by Alexandra Hogan (Alexandra Hogan) from Imperial College London, the effectiveness of the vaccine, i.e. its ability to block the transmission of the virus is 90%; to develop temporary herd immunity, it is necessary to vaccinate at least 55% of the population; at the same time, in order to contain the transmission of coronavirus, some social distancing measures need to be maintained, including mask mode as well as remote operation. (If all social distancing measures were abolished, then vaccination would need to reach almost 67% of the population to develop herd immunity.)
But if, due to the appearance of a new modification of the coronavirus, the rate of its transmission increases, or if the effectiveness of the vaccine does not reach 90%, then in this case, in order to prevent the spread of coronavirus, it will be necessary to increase the coverage of the population during vaccination.
In many countries it will be difficult to vaccinate even 55%. “If the population is not vaccinated in some parts of the world, the coronavirus will not go away,” says Jeffrey Shaman, an infectious disease specialist at Columbia University in New York.
Even if the current coronavirus remains endemic in many regions of the world, then, according to Christopher Dye, the movement of people from one region to another is still likely to resume after the following conditions are met: firstly, after the number of severe infectious infections decreases to a level that the health care system can easily cope with, and, secondly, after vaccination has reached the majority of people vulnerable to severe forms of coronavirus infection.
Does it look like the flu?
The influenza pandemic, which broke out in 1918 and killed more than 50 million people, is a criterion for judging all other pandemics. The Spanish flu was caused by the influenza A virus, which originally appeared in birds. Since then, almost all cases of influenza A, as well as all subsequent influenza pandemics, have been caused by the descendants of the same virus that appeared in 1918. New modifications of this virus have spread across the globe and infect millions of people every year.
Influenza pandemics occur when the public does not consider the influenza virus to be a serious threat; by the time a pandemic virus becomes seasonal, most of the population has developed immunity to it. Seasonal flu continues to wreak havoc on a global scale, claiming an estimated 650,000 lives annually.
Evolutionary biologist Jesse Bloom of the Dr. Freda Hutchinson in Seattle believes that the same story can happen with the current coronavirus in the future as with the flu virus. “I really think that the virulence of the SARS-CoV-2 coronavirus will subsequently decline. It will resemble something like the flu,”says Bloom. Jeffrey Shaiman and others also believe that the current coronavirus will turn into one of the seasonal flu-like illnesses.
The flu appears to be able to mutate much faster than SARS-CoV-2, allowing it to seep through the human immune system. It is for this reason that influenza vaccines need to be modified annually; however, it is possible that the SARS-CoV-2 coronavirus vaccines are not in danger.
Nevertheless, the coronavirus is capable of deceiving the immunity acquired by the body as a result of infection, and perhaps even as a result of vaccination. Laboratory studies have shown that the ability of antibodies that appeared in the blood of people who have had covid-19 to recognize the type of coronavirus that was first discovered in South Africa (called 501Y. V2) is reduced, compared to the ability to detect those variants of the coronavirus. which were previously common during a pandemic.
This is probably due to mutations in the spike protein of the coronavirus, against which, in fact, vaccines were created. According to the test results, the effectiveness of some vaccines against the coronavirus 501Y. V2 is lower than against other variants of the coronavirus; some of the vaccine manufacturers are exploring the possibility of modifying their products.
However, as Jenny Lavigne explains, the human immune system has many advantages; for example, it is able to recognize, in addition to the spines (spikes), and many other characteristics of the virus and respond to them. "The virus will likely have to mutate multiple times to invalidate the vaccine," Lavigne said. As shown by preliminary test results, explains Angela Rasmussen, vaccines are able to protect a person infected with the 501Y. V2 virus from severe infection.
More than 70% of researchers surveyed by the journal Nature believe that the ability of the coronavirus to overcome immune defense mechanisms will be another factor that will further the spread of this coronavirus. In general, the current coronavirus is not the first that humanity has encountered.
So, for example, in one article that has not yet been peer reviewed, Jesse Bloom and colleagues showed that the endemic coronavirus 229E was able to mutate to such an extent that the effectiveness of neutralizing antibodies in the blood of people infected with this viral variant (it spread in the late 1980s - the beginning of the 1990s), when meeting with later modifications of viruses decreased significantly.
People are now re-infected with coronavirus variant 229E during their lifetime; Based on this fact, Bloom argues the following: it is quite possible that it will be more difficult for specialists to prevent infection with viral variants that have evolved so much that they are able to fight previously developed immunity. However, scientists cannot decide whether these re-infections are associated with worsening symptoms. “It seems to me that thanks to the mutations that have accumulated over the years, the SARS-CoV-2 coronavirus will deal an even more powerful blow, neutralizing the immune defense from antibodies, as was the case with CoV-229E.
True, I cannot say for sure which of the two coronaviruses will be stronger,”says Bloom.
According to Jesse Bloom, it is likely that the SARS-CoV-2 vaccines will need to be modified, and perhaps annually. But even in this case, the immunity formed under the influence of a previous modification of the vaccine or as a result of an infectious infection, according to Bloom, will probably help prevent a serious course of the disease. Jenny Lavigne notes that even if a person gets infected again, then there is no need to worry.
In the case of endemic coronaviruses, she said, frequent re-infections appear to boost immunity against related viral variants; in this case, the infection, as a rule, manifests itself in a person only in a mild form. But it is quite possible that in some people, according to Jeffrey Shaman, the disease will be severe even after vaccination; in this case, the coronavirus will continue to threaten our society.
If vaccines against SARS-CoV-2 prove to be able to protect the human body from coronavirus for life and prevent its spread, then SARS-CoV-2 will look like a measles virus as a result. “Such a development [unlike other scenarios] is unlikely, but still possible,” says Jeffrey Shaman.
Thanks to a highly effective measles vaccine (two doses can protect a person for life), the measles virus has been eradicated in many parts of the world. Before the vaccine was introduced in 1963, major measles epidemics killed about 2.6 million people every year, mostly children. Unlike influenza vaccines, the measles vaccine does not need to be upgraded because the measles virus has not yet been able to mutate enough to outsmart the immune system.
However, in some regions of the world that have not been sufficiently affected by immunization, measles remains endemic. In 2018, as soon as measles began to reappear globally, more than 140,000 people died from the disease. A similar situation can arise with the SARS-CoV-2 coronavirus if the population neglects vaccination.
A survey of more than 1,600 US citizens showed that more than a quarter of them would definitely or, depending on certain conditions, refuse to vaccinate against covid-19, even if such vaccination was free and safe. “How successfully we can solve these problems will determine the proportion of the vaccinated population, as well as the proportion of the population vulnerable to the coronavirus,” says Angela Rasmussen.
Animals as reservoirs of the causative agent of infection
What will happen to the SARS-CoV-2 coronavirus in the future? Everything will depend on whether it will take root in the population of wild animals. Some diseases that are brought under control, however, do not disappear anywhere, because reservoir animals, such as insects, are capable of infecting humans again and again with various infections, such as yellow fever, Ebola and chikungunya.
It is likely that the SARS-CoV-2 virus originally appeared in bats, and then it could be transmitted to humans through an intermediate carrier. The coronavirus can easily infect many animals, including cats, rabbits and hamsters. It is especially dangerous for minks, and massive outbreaks of infectious infections on mink farms in Denmark and the Netherlands have led to large-scale culling of these animals. Coronavirus can also be transmitted from mink to humans and vice versa.
According to epidemiologist Michael Osterholm, if this coronavirus took root in a population of wild animals, and then return back to humans, it would be extremely difficult to control this coronavirus. “In the history of mankind, virtually all diseases that have disappeared to date have arisen - in whole or in part - due to pathogens transmitted from animals to humans,” says Osterholm.
To date, it is difficult to say how the SARS-CoV-2 coronavirus will become endemic, but society is to some extent holding back its spread. In the next year or two, the world community with the help of special measures will be able to prevent the spread of viruses from animals to humans; this will continue until a sufficiently large part of the population is vaccinated in order to develop herd immunity, or to significantly reduce the severity of infectious diseases.
Such measures, according to Osterholm, will significantly reduce mortality and the number of serious illnesses. But if countries abandon the strategies that could contain the spread of the coronavirus and allow it to infect the population uncontrollably, then in this case, Osterholm sums up, “in the end we will have the most bleak prospects.”
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