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All vaccines don’t work the same way, the smallpox vaccine we talked about earlier works because the cowpox virus and the smallpox virus come from the same genus Orthopoxvirus in the family Poxviridae, which tricks the immune system into thinking both of them as the same virus. Today, we have vaccines that share the same basic principles but are different in their own right, we shall discuss them in the following paragraph.
Before the COVID-19 pandemic, there used to be 4 types of vaccines in mass production, but before that, we need to understand how the immune system recognizes the virus in the first place.
How immune system recognizes virus?
The immune system in mammals, along with most animals is a fairly complex one, but in this article, we’ll just cover a couple of types of cells, namely, T cells(Thymus cells) and B cells(Bone marrow cells).
B cells helps the immune system by destroying the foreign materials, or pathogens and T cells are responsible for cell mediated immunity which means an immune system that doesn't involve antibodies.
When the body faces a foreign threat, and it starts to get out of control, the body calls the T and B cells, a helper T cell then binds to the M.H.C.s(Major histocompatibility complex), when they’re all reduced to small particles and displayed by other immune cells, T cell(the helper) then makes multiple copies of themselves while making memory T cells too which can recognize the virus or bacteria when it comes around in the future. Along with T cells, you also have B cells that project antibodies that can bind to a specific antigen. So, let’s say that one of your B cells encounters a flu virus and has the specific antigen that its antibody can bind to, it makes many copies of itself that carry the same antibody (like a key to the ‘door’ that attaches to a pathogen), most are effector cells, some are memory B cells that lie around so that it can recognize the pathogen when it has an encounter with the pathogen in the future.
The effector cells flood the blood with antibodies that flag the pathogens and make it easier for the macrophages to come around and gobble them up.
So, what does this have to do with vaccines? Actually, a lot. When you are intentionally injected with a pathogen, say in a vaccine, and knowing the secondary response is much faster than the primary one, you are preparing your immune system so that it can fight a pathogen without you ever knowing it in its secondary response. Vaccines contain weakened, dead, or attenuated (where the ability of a cell to invade other cells or reproduce has been eliminated or reduced to such extent that it doesn’t matter much) versions of viruses that can’t cause a severe infection.
Types of Vaccines
The first 2 types are the most prevalent ones, the vaccines have either a weakened version of the virus or a completely inactive one, the immune system still recognizes the virus as foreign and will 'remember' how to fight it the next time it comes around.
Some examples of these types of vaccines will be the measles vaccine which uses a weakened version of the virus and the annual flu vaccine that uses the completely inactive vaccines respectively.
The other kind is a lesser-used one, it involves injecting a toxin in a body that makes the immune system immunized, the tetanus vaccine is one of the types of vaccines that uses this method.
The fourth method is a little different from the three mentioned above, the vaccine consists of a part of the virus, like the spike protein of the novel coronavirus (SARS CoV-2), the body still recognizes the pathogen in the future and you become immunized.
The other two types of vaccines that we’ll be discussing are the newest kinds of vaccines around and can likely revolutionize the way future vaccines will be made.
Let’s first look at the way Pfizer-BioNTech and Moderna vaccines work, they’re called mRNA vaccines.
How do the latest mRNA vaccines work?
The mRNA that makes the spike proteins is identified and is synthesized, the mRNA is used as the vaccine here. When it is injected into the body and a cell reads it and starts making the SARS CoV-2 spike proteins, the immune cells then recognizes it and remembers it, therefore immunizing you, but however, the mRNA has to be ‘kept’ inside a fatty membrane (and fatty liquids in the inside of it too) so that it doesn’t disintegrate, so, it has to be kept in a super cold environment, the Moderna vaccine, for example, has to be kept in around -4°F (-20°C) where it can last for up to 6 months.
The poorer countries don’t have a vaccine cold chain to keep this kind of vaccine so, it makes a vaccine unreachable to the poorer sections of the world.
How are J&J and AstraZeneca different from mRNA vaccines?
The other type of vaccine is used by Johnson and Johnson and AstraZeneca solves this problem. They’ve pioneered a different technique that requires nothing more than the usual vaccine cold storage chain and it’s fairly cheap to produce. This vaccine involves taking the DNA of the SARS CoV-2 and puts it in a different harmless carrier, here, it is a weakened adenovirus (a type of common cold in chimpanzees). It carries the DNA of the SARS CoV-2 and when a human is administered the vaccine, they don’t get an infection, but the human immune system recognizes the SARS CoV-2 DNA, and becomes ready for the real thing. This vaccine, however, has a drawback, when the same carrier is used over and over again, the human immune system builds immunity against the carrier itself, and therefore, the carrier has to be changed regularly.
How do we compare their efficacy?
The next thing that comes to our minds is “How effective are these vaccines?” or “Will I ever get COVID-19 after I get vaccinated?” We will answer both of these questions in this section, but first, we should figure out what determines the effectiveness of these vaccines and whether these matter at all to the general public?
All of us have probably heard that the ‘efficacy rate’ or ‘effectiveness’ of the Pfizer-BioNTech vaccine is 95% or the Johnson and Johnson has a 66.3% efficacy rate, the efficacy rates here are being used to compare the different kinds of vaccines, so in order to get a clearer picture, we’ll need to look at how they’re actually formulated.
When large clinical trials are being done, involving tens of thousands of people, the people are divided into 2 groups, half of the people get the vaccine and half get a placebo, the people aren’t told whether they have got the vaccine or the placebo, and all of them go back to their usual lives, exposing them to COVID-19. These people are then monitored for several months, to see how many people got the disease. So, let’s take an example of a fictitious vaccine, say X vaccine where 100,000 people participate in its clinical trial. Imagine after 4 months 200 people got COVID-19, now, we’ll look at the breakup of the cases. If the cases are divided equally among the people who’ve been given the placebo and the vaccine respectively, 100 each, then, the X vaccine will have a 0% efficacy rate, that is, you’re just as likely to get COVID-19 without the vaccine. If all of the people who’ve tested positive for COVID-19 are the ones who’ve got the vaccine, then you’ll know that the vaccine has an efficacy rate of -100% (-100% not a 100%) and it increases your chances of getting the virus. This could either mean that the X vaccine is a total disaster or that only the people who’ve got the vaccine got exposed to the virus, with the chances of the latter occurring is remarkably rare. Keep in mind that vaccines this bad don’t exist.
And if all the people who’ve got COVID-19 are from the placebo group, then, the vaccine has an efficacy rate of a 100% and is likely very effective.
Now, let’s look at Pfizer-BioNTech’s clinical trial, out of the 43,000 people who took part in this trial, only 170 people contracted COVID-19. 162 of these people were given the placebo and only 8 vaccinated people got COVID-19, this gives the Pfizer-BioNTech vaccine a 95% efficacy rate.
This doesn’t mean that 5 out of 100 people administered with the Pfizer-BioNTech will get COVID-19, it means that an individual is 95% less likely to get COVID-19 than a person who is not vaccinated.
This doesn’t always mean that a vaccine with a higher efficacy is always better than a vaccine with a lower efficacy rate, it all depends on the circumstances when the trial was taking place. Look at the number of cases when the Moderna and Pfizer-BioNTech trials were taking place, (Moderna trials were completely based in the US and Pfizer had most of their trials in the US) vs when the Johnson & Johnson trials were happening, you’d be more likely to get COVID-19 during the time when the Johnson& Johnson trials were taking place, as there was a massive rise in the number of cases. The Johnson & Johnson trials were also taking place in South Africa and Brazil, where new variants of COVID-19 were becoming common. This did reduce Johnson & Johnson’s vaccine’s efficacy rate, but it proved to be very efficient against the new COVID-19 variants as most of the vaccinated people who contracted COVID-19 had the newer variant and yet had a 66.3% efficacy rate, thus making it a very ‘good’ option against the new variants too.
Before we make any rash conclusions, we must keep in mind that what these vaccines aim to do is mostly make COVID-19 a rather less fatal disease, their efficacy rates shouldn’t keep us from getting the shots.
Out of all of the people who took the vaccines, none were hospitalized, and of course, there was a 0 fatality rate, so all these vaccines save your life, no matter what their efficacy rates are, and coming back to the question we asked at the beginning of this section, the answer of the first will be, “Don’t care how effective the vaccine when it comes to keeping you from getting COVID-19, just get yourself vaccinated as soon as you can, it is there to save your life and keep you from ‘taking a tour of a hospital ICU”, and I think the second question has been answered along with the first.
I would like to conclude by saying that put your trust in the scientists, doctors, etc who’re working hard to make these vaccines, and that all vaccines have a ‘100% efficacy’ when it comes to severely limiting your chances of developing critical symptoms and if you’re vaccinated, there’s a virtually 0 chance of you getting hospitalized for contracting COVID-19.
You can also watch the video below if you want to understand this blog through a video.
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Tags: #covid
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