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Bonuses on a DVD or Blu-ray disc (remember that?) Are cool, but we don’t expect them from vaccines. As the new coronavirus swept through communities in 2020 and no specific vaccine was on the immediate horizon, scientists began to wonder if a different vaccine, already approved and commonly administered, might have any benefit in self: protect ourselves from COVID and its most serious consequences. The vaccine in question is the flu shot, and with the flu season approaching the northern hemisphere, it’s worth examining the scientific evidence behind this idea that the flu vaccine might not be. only protect against influenza but also COVID.
At the start of the pandemic, however, some feared that being vaccinated against the flu might actually have the opposite effect. The basis for this fear was a scientific article published just before the start of the pandemic by Greg G. Wolff, epidemiologist for the Armed Forces Health Surveillance Branch in the United States. He analyzed some figures from the 2017-18 flu season and reported, in a calculation, that Defense Ministry staff who had received their flu shot were more likely to catch coronavirus. A coronavirus before the emergence of COVID? Well yes. SARS-CoV-2 isn’t the only coronavirus in town; coronaviruses have given us SARS and MERS in the past, and a handful of them are responsible for many cases of what we call the common cold. So in this analysis, getting the flu shot apparently puts you at an increased risk of getting a mild cold from coronavirus. Some have wondered if that means being immune to the flu during the COVID-19 pandemic would be a weakness, not a boon.
There was one big problem with this association, however: it was not real. A Canadian team showed Wolff made a mistake. He had dutifully removed people who tested positive for influenza from the control group in a scan, but in the scan that led to the alarming result, he mistakenly kept those people indoors. When the Canadian team reanalyzed Wolff’s numbers and looked at seven years of Canadian data, the distressing association disappeared. In our age of global disinformation, studies with frightening results, even when debunked or retracted, are militarized by activists, and Wolff’s study is no exception. Wolff himself wrote a letter to the editor of the journal that published his original study stating clearly that his “DO NOT” results, as he wrote in all capitals, “support the consistent anti-vaccination point of view. to avoid vaccination against seasonal influenza ”.
But eventually, teams of scientists began to report an unexpected trend: Not only did the flu vaccine not promote COVID infections, as briefly feared, it could actually protect against them.
Marginal profit or mirage?
The idea is quite simple at first glance: you look in medical databases at two groups of people, those who are registered as having received their flu shot and those who do not, and you compare the two groups for see how many in each of them were later diagnosed with COVID, how many were hospitalized because of it and how many died from it. Another way is to do the reverse, start with people diagnosed with COVID, see how many have had the flu shot and how many haven’t, and look at how each group is doing. These types of studies have been done and many have reported that the flu vaccine appeared to have offered some protection either against COVID itself or against serious illness. How many protections? The authors of these articles describe it as “relatively small” and “marginal”. The word “may” is used a lot.
Other studies, conducted mainly in Italy, do not find such a link, and here we are faced with the difficulties of obtaining reliable results from studies like these. Our best chance for clarity would be to do a randomized controlled trial, in which participants are randomly assigned to either receive a flu shot or be denied the vaccine. To be extra-rigorous, we would then deliberately expose all of these people to the coronavirus to document what would happen. Needless to say, there is a good word to describe this experience: unethical.
Scientists are therefore stuck comparing groups of people who selected to receive a flu shot or not, but are these people really comparable? Studies which find a protective effect of the vaccine may have come to this result due to what is called healthy user bias. People who seek the flu shot may be more health conscious than those who don’t. They may be more likely to follow public health guidelines. They may also be better off financially and able to take the time to get vaccinated and pay for the vaccine.
As such, it is possible that what some scientists are actually seeing is not a vaccine with a bonus, but simply individuals who tend to wear their masks, keep their distance from potentially infectious people, and take better care of them. of their health. And researchers are the first to point out this alternative explanation. Studies are never perfect, and it’s always helpful to scroll down to the end of the discussion section of an article to learn more about the limits of the job. A small number of participants. A particular population, making the results difficult to generalize. The possibility of confounding factors, that is, a third factor, not studied by scientists, which gives the impression that A causes B when in fact it is not. It’s important to point out the limitations, and the influenza vaccine literature potentially protecting people from the worst of COVIDs is no exception. It is therefore possible that the influenza vaccine does not offer specific protection against COVID-19.
But if the flu vaccine is ultimately shown to have a clear protective halo that encompasses COVID (and possibly other infections as well), it may be through a process known as trained immunity, an idea that changed the way we think about what the immune system is capable of.
In the living memory of the innate immune system
Our immune system can be divided into two branches. Our adaptive immunity can use antibodies to tailor its defense against a specific invader and it forms a memory of that invasion. Our innate immunity, on the other hand, is more primitive and nonspecific. It uses barriers, molecular bombs and starving cells that devour microbes. We used to think that this innate immunity had no memory of these attacks and therefore couldn’t learn, but an emerging body of work says, “not so fast”.
It all started with the tuberculosis vaccine. Scientists saw that receiving this vaccine was associated with a decrease in deaths that could not be fully explained by protection against tuberculosis. The vaccine also seemed, strangely enough, to protect against unrelated respiratory infections and sepsis. A parallel finding was reported in mice, which showed that this additional characteristic was not channeled by the adaptive immune system, but rather by the innate response. This phenomenon has been called trained immunity.
Basically, a challenge is presented to our immune system. This challenge is a microbe or part of a microbe, like the attenuated tuberculosis vaccine or a sugar like beta-glucan present in the cell wall of a fungus. When these microbial elements come into contact with our immune system, it sends ripples throughout the system, reprogramming that makes our innate immunity better able to respond to a future attack. A parallel drive mechanism has been well established for our adaptive immunity, with its antibodies and memory cells, but the fact that our raw innate immune response is also capable of this is unexpected.
Reprogramming itself is epigenetic in nature. Our genes make proteins, but they don’t always make proteins. Like bakers, they have schedules and they respond to dips and increases in demand. This regulation is under the control of epigenetic factors: marks which land on genes to silence them and large molecules which can relax or crumple the DNA molecule to make it more or less accessible. Scientists are only now beginning to understand how epigenetic reprogramming by infectious agents can train our innate immunity to better protect us from unrelated contagions. Some live attenuated vaccines, such as those against smallpox, measles, yellow fever, and polio (the live oral version but not the inactivated vaccine), have been shown to trigger this induced immunity, and future research should reveal which others vaccines might have provided us with this bonus feature all along.
We still don’t know for sure if the flu vaccine really offers some protection against COVID-19 and its complications. The benefit may be real albeit marginal, or it may simply be an illusion created by flawed studies done to investigate this effect. Either way, the flu shot has real benefits. It protects against the flu, a disease that some say will be severe in the coming winter season due to our diminished immunity from not having encountered the virus much last year. And the flu shot helps reduce hospitalizations from the flu. Given the number of times our health care system of exhausted people has groaned and flexed under the stress of the pandemic, every little preventive action helps.
Takeaway message:
-The claim that getting a flu shot puts you at risk of COVID-19 is not true and was based on an article published before the pandemic that made a mistake when calculating the risk of coronavirus infection in people who had been immunized to the flu
-There is conflicting evidence as to whether or not the flu shot provides little protection against COVID-19, as this effect may simply be due to the fact that people seeking the flu shot are more health conscious, the better financially and more willing to adopt public health measures during the pandemic
-Some infections and vaccines seem to be able to improve our defenses against other infections by training a part of our immune system that we thought was incapable of this kind of training
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