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Why proposals to let the virus run its course, followed by the management of Donald Trump and others, are a false promise
In May, the Brazilian city of Manaus was devastated by a primary outbreak of COVID-19, hospitals were hit and the city dug new cemeteries in the surrounding forest, but until August, everything had changed. Despite the reduction in social estating needs in early June, the city of 2 million people reduced its excess deaths from approximately 120 per day to near zero.
In September, two teams of researchers published preliminary prints suggesting that the summer slowdown in COVID-19 instances occurred, at least in part, because a giant part of the community population had already been exposed to the virus and was now immune. Ester Sabino of the University of Sao Paulo, Brazil, and his colleagues analyzed more than 6,000 samples from Manaus blood banks for anti-SRAS-CoV-2 antibodies.
“We showed that the number of other people inflamed was actually higher, reaching 66% at the end of the first wave,” Sabino says. His organization concluded that this higher infection rate meant that the number of others still vulnerable to the virus was too small for new outbreaks, a phenomenon called collective immunity. Another Brazilian organization came to similar conclusions.
These manaus reports, as well as similar arguments about the spaces in Italy that were hit hard at the start of the pandemic, have helped embolden proposals to seek collective immunity. to the maximums at risk of serious illness. This would necessarily allow the coronavirus to run its course, the supporters said.
But epidemiologists have continually criticized such ideas. ” Reaching the virus” is not a defensible plan, says Kristian Andersen, an immunologist at the Scripps Research Institute in La Jolla, California. Such a technique would result in a catastrophic loss of human life without necessarily accelerating society’s return to normal, he said. “We have never been doing this before, and this will result in unacceptable and unnecessary human death and suffering. “
Despite widespread criticism, the concept continues to emerge among politicians and policymakers in many countries, adding Sweden, the United Kingdom and the United States. U. S. President Donald Trump spoke definitively about it in September, employing the “herd mentality” of malapropism. even a few scientists have pushed the agenda. In early October, a libertarian expert group and a small organization of scientists published an article called the Barrington Grand Declaration, in which they call for a return to general life for others with little serious COVID-19 threat, in order to allow SARS-CoV-2 to spread to a point sufficient to grant collective immunity. High-threat people, such as the elderly, he said, can be protected through measures that are largely uns specified. The White House hearing triggered a countermemoria from some other organization of scientists in The Lancet, who called the technique of collective immunity a “dangerous mistake without the backing of clinical evidence. “
The arguments in favor of allowing the virus to run largely uncontrolled represent a false impression of what collective immunity is and how productive it is to achieve it. Here, nature answers five questions about the questionable idea.
Collective immunity occurs when a virus cannot spread because it continues to find others who oppose the infection. Once a sufficient proportion of the population is no longer sensitive, any new outbreaks disappear. “You don’t want everyone in the population to be immune – all you want is enough people to be empt,” says Caroline Buckee, epidemiologist at Harvard’s THChan School of Public Health in Boston, Massachusetts.
As a general rule, collective immunity is a desirable end result of large-scale immunization programs. High degrees of immunization-induced immunity in the population gain benefits for those who cannot get or respond sufficiently to a vaccine, as others with many fitness professionals hate the term collective immunity and prefer to call it “collective protection,” Buckee says. This is because the phenomenon does not confer immunity to the virus itself, it only reduces the threat of other vulnerable people touching the pathogen.
But public fitness experts sometimes don’t communicate about collective immunity as a tool in the absence of vaccines. “I’m a little lost for the words that this now means how many other people have to be inflamed before this stops,” says Marcel Salathé, epidemiologist at the Federal Polytechnic School of Lausanne.
Epidemiologists can estimate the proportion of a population that will have to be immunized before herd immunity is effective. This threshold is based on the number of baseline replicates, R0, the number of cases, on average, generated across an inflamed individual in a well-mixed population, says Kin On Kwok, an infectious disease epidemiologist and mathematical modeler at the University. China from China. Hong Kong. The formula for calculating the herd immunity threshold is 1–1 / R0, which means that the more people become inflamed with each individual carrying the virus, the greater the proportion of the population that will have to be immunized to achieve immunity. collective is high. For example, measles is incredibly contagious, with an R0 regularly between 12 and 18, which corresponds to a herd immunity threshold of 92-94% of the population. For a less infectious virus (with a reduced number of replicas), the threshold would be lower. The R0 assumes everyone is vulnerable to the virus, however this adapts as the epidemic progresses as some other people become inflamed and gain immunity. For this reason, in these calculations a variation of R0 called effective R (abbreviated Rt or Re) is used, since it takes into account the sensitivity adjustments in the population.
Although entering numbers into the formula yields a theoretical number of collective immunity, it is not actually achieved at a precise moment, but it is better to think of it as a gradient, says Gypsyamber D’Souza, epidemiologist at Johns Hopkins. University in Baltimore, Maryland. And because variables can change, adding R0 and the number of other people vulnerable to a virus, collective immunity is not a state of balance.
Even once collective immunity is achieved in a population, it is still imaginable to have giant outbreaks, as in spaces with low vaccination rates. “We have noticed that this is happening in some countries where incorrect information on vaccine protection has been extended,” Salathé says. “In local pockets, you start to see a drop in vaccines, and then you may have local epidemics that can be very important, even if you’ve technically achieved collective immunity by calculations. “The ultimate purpose is to prevent other people from getting sick, rather than achieving a secure number in a pattern.
Collective immunity depends on what is happening in the population. Threshold calculations are very sensitive to R values, Kwok says. In June, he and his colleagues published a letter to the editor in the Journal of Infection that proves it. Kwok and his team estimated rt in more than 30 countries, using knowledge on the daily number of new COVID-19 instances since March. They then used these values to calculate a threshold for collective immunity in the population of each country. The figures ranged from 85% in Bahrain, with a Rt of 6. 64 at the time, to 5. 66% in Kuwait, where rt was 1. 06. Kuwait’s low numbers reflect the fact that it is implementing measures to combat the virus, such as ingesting local curfews and banning advertising flights from many countries. If the country stopped these measures, Kwok said, the threshold for collective immunity would increase.
Collective immunity calculations like those in Kwok’s example are based on hypotheses that might not reflect genuine life, says Samuel Scarpino, a network scientist who studies infectious diseases at Northeastern University in Boston, Massachusetts. “Most calculations of collective immunity have nothing to do with saying about habit. They assume there are no interventions, no behavioral adjustments or anything like that,” he says. This means that if a brief replacement in people’s behavior (such as physical distance) reduces rt, then “as soon as this habit returns to normal, the threshold of collective immunity will replace it. “
SarS-CoV-2 diversity threshold estimates from 10% to 70% or more, but models that calculate numbers at the lower end of this diversity are based on assumptions about how other people interact on social media that might not be true. Scarpino says. Low result estimates recommend that others with many contacts become inflamed first and that because they have a large number of contacts, they will transmit the virus to more people. As these “superpropagators” gain immunity against the virus, the chains of transmission among which they are still delicate are particularly less finished. And “as a result, it is achieved on the threshold of collective immunity very quickly,” Scarpino says. But if it turns out that anyone can just a super then “the assumptions that other people depend on to reduce estimates to around 20 or 30% are simply not accurate,” Scarpino explains. The result is that the collective immunity threshold will be closer to 60-70%, which is what maximum model visualization (see, for example, ref. 6).
If widespread known occasions are observed in prisons and cruise ships, it is transparent that COVID-19 spreads widely from the outset, before declining in a captive and un vaccinated population, Andersen says. At San Quentin State Prison in California, more than 60 percent of the population was still inflamed before the outbreak stopped, so it wasn’t as if it had magically stopped after 30 percent of others contracted the virus, Andersen said. “There is no mysterious dark matter to protect other friends,” he says.
And while scientists can estimate the thresholds for collective immunity, they may not know the actual figures in real time, says Caitlin Rivers, epidemiologist at the Johns Hopkins Center for Health Security in Baltimore. Collective immunity, on the other hand, is anything that can only be observed with certainty by analyzing knowledge retrospectively, perhaps up to ten years later, he says.
Many researchers say that herd immunity is a bad idea. “Trying to achieve herd immunity through targeted infections is just ridiculous,” says Andersen. “In the United States, one to two million more people would die. “
In Manaus, mortality rates in the first week of May rose to four-and-a-half times what they had been last year, and despite enthusiasm for the August slowdown, the numbers appear to be emerging again. The hypothesis that the population of Manaus has achieved collective immunity “is simply not true,” Andersen says.
Deaths are just one component of the equation. People with the disease can suffer serious medical and monetary consequences, and many others who have recovered from the virus report persistent effects on fitness. More than 58,000 other people have become inflamed with SARS-CoV-2 in Manaus, resulting in widespread human suffering.
At the beginning of the pandemic, the media claimed that Sweden was following a strategy of herd immunity by necessarily letting other people live their lives normally, but the concept is a ‘misunderstanding’, according to the UK Minister for Health and Welfare. . country, Lena Hallengren. Herd immunity “is a prospective result of how the spread of the virus is unfolding, in Sweden or in any other country,” he told Nature in a written statement, but “it is not a component of it. Our strategy. ” Sweden’s approach, she said, uses equipment similar to other countries at most: “Promote social distancing, protect other vulnerable people, test and trace contacts and strengthen our system. Aptitude to cope with the pandemic. ” Despite this, Sweden is not a style of good fortune: statistics from Johns Hopkins University show that the country has recorded more than ten times the number of deaths from COVID-19, in line with another 100,000 people in neighboring Norway. ) Array Sweden’s case fatality rate, which is based on the number of known infections, is also at least 3 times higher than that of Norway and neighboring Denmark.
The concept of collective immunity through the network spread of a pathogen is based on the unproven assumption that other infected people will become immune. For SARS-CoV-2, some kind of functional immunity turns out to adhere to the infection, but “to perceive the duration and effects of the immune response, we want to stick to other people longitudinally, and we are still in the early stages,” buckee says.
Rivers says there is also no foolproof way to measure immunity to the virus. Researchers can check if others have antibodies expressed against SARS-CoV-2, but they still don’t know how long immunity can last. causes reduction in immunity that seems to last about a year, Buckee says. “It is moderate to assume that this will be similar. “
In recent months, there have been reports of others re-inflamed with SARS-CoV-2 after an initial infection, however, how these reinfections occur and whether they cause less serious illnesses remain open questions, Andersen says. “If other inflamed people become sensitive in a year, then it will essentially never achieve “collective immunity” through herbal transmission, Rivers says.
“There’s no magic wand we can use here,” Andersen says. “We have to face the truth, we have never before achieved collective immunity through an herbal infection with a new virus, and SARS-CoV-2 unfortunately is no different. “Vaccination is the only moral pathway to collective immunity, he says. The number of other people who want to be vaccinated – and the frequency – will have many factors, adding up to the effectiveness of the vaccine and the duration of its protection.
People are naturally tired and frustrated by measures imposed such as social estating and closures to the spread of COVID-19, but until there is a vaccine, those are some of the most productive equipment available. “It is not inevitable that we will all have to get this infection,” says D’Souza. “There are many reasons to be very optimistic. If we can continue threat mitigation approaches until we have an effective vaccine, we can surely save lives.
This article is reproduced with permission and was first published on October 21, 2020.
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