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Vaccines. How do they work? Or do they work at all? How are they made? Why do we have so many vaccines and why is the entire world so focused on getting one right now? These are all very important things to understand, especially in the times of this pandemic… When all of us are impatiently watching the pharmaceutical industry getting the COVID-19 vaccine ready for the world. If you would like to learn everything you need to know about vaccines, keep on reading!
I wanted to dedicate this post to Kamil Sękulski, who suggested that I write about this topic. Kamil, this post is for you – thank you so much for your suggestion!
In a nutshell, vaccines help boost our immune system (you know, the “defense” of our body against germs). So before I dive into more details, we need a little introduction to how the human immune system works in the first place. If you have ever played a military-based strategy game (like “Age of Empires”, which I absolutely love) or at least if you have watched the “Game of Thrones”, you might find it easier to understand. If not, don’t worry – just bare with me and I am sure we will soon all be on the same page!
The human body has three layers of defense against germ invaders
Like you all know, our bodies have to fight germs in one way or another… Pretty much every day! There are three types of immune system cells (the defense I have been referring to), which are used as soldiers in this fight:
– Macrophages
– B-type lymphocytes (or just B Cells)
– T-type lymphocytes (or simply T Cells)
All these cells can be found in our blood! And what’s most interesting, they are all collectively called “white blood cells”, as if the blood was white at all!? Yes, there are red blood cells too, and those are responsible for the color of your blood. They carry oxygen to all the organs in your body. We can also find blood platelets in the blood, which help wounds heal:
But here we are talking about the unsung heroes – the White Blood Cells, which do not give your blood its cool color and do not help the wounds heal. These cells are absolutely invaluable little soldiers in your immune system. I hope you will start appreciating them more from now on! You can imagine macrophages as the giants from the “Game of Thrones” (or really, any other type of giant fighters). They can quite literally swallow up and digest the entire germs or even dead cells of your own. Take a look at this microscopy video of a real white blood cell chasing a becterium, to eat it:
After they are done with their job, they leave some traces of their fight – parts of their victim, the invading germ. Thanks to that, the B-type lymphocytes can recognize these bits and pieces and based on that trace, they can remember what these germs are, to quickly recognize them the next time they decide to attack. This is a way your B cells can build the immune memory.
Source of the image: shot from “Game of Thrones”
Finally, T-type lymphocytes are very special cells that can kill your own cells if these have already been infected. See? It really is a three-layer defense system: 1) macrophages, 2) B cells and 3) T cells. Add washing your hands and wearing a mask as an extra layer and your white blood cells will definitely be grateful that they don’t have to keep fighting all the time.
The B Cells can make specialized antibodies against specific germs
The first time your body meets a new germ, it can take a little longer for it to build up the defense (just like the reaction of an army won’t be as good to a surprise attack). In the time of building up the defense, your body might become ill. However, after the first infection has been dealt with, our body remembers how to fight this specific type of germ in the future – the time of this memory differs from one type of germ to another. This is all thanks to the B-type lymphocytes that you just read about in the last few paragraphs. These B cells, now remembering the germ’s characteristic features (which we will call “antigens” from now on), can start making antibodies. And the antibodies are what triggers the rest of the immune system to act quickly.
Vaccines help prepare our immune system to protect the body from different germs
You might think that with all this cool and sophisticated defense system, your body should be fine. Unfortunately over the years, history has proven otherwise. Luckily, these days we have vaccines, which can provide additional defense for your organism. The general idea behind how vaccines work is very similar, independent of the vaccine type: you receive pieces of the germ (the antigens), so that your B cells can start making antibodies without your body being actually infected! Some newer vaccines only contain a blueprint of the antigen, so that your smart body can make that antigen itself! Even safer! Sometimes the reaction of your body to the vaccine can cause mild, short-term fever and you might feel a little achy. This is not you becoming sick after the vaccine, but it is your immune system being busy making all these antibodies and building up the memory cells. So the “feeling under the weather” for one or two days after a flu shot is nowhere close to the actual flu. Maybe it will help to ease your post-vaccine suffering a little more, if I remind you that thanks to the different miraculous vaccines we have been able to eradicate or at least very well control many infectious diseases, including for example: smallpox, polio, measles, diphtheria, tetanus, rubella, typhoid, to name just a few!
Additionally, in response to the vaccine, some of your B cells will become so-called “memory cells“, which are very specialized and able to get activated super quickly in case of any subsequent infection. Now, these memory cells are one of the reasons why some vaccines need to be taken only once while others need a few repeated doses – months or sometimes years apart. Whether the extra boost for your immune system (in the form of an extra vaccine dose) is necessary and when it should be taken, is all dependent on the disease you are trying to prevent. Remember to always stay on top of your “booster” doses, because they will trigger your body to make more of the memory cells as well as longer-lived antibodies. In this way you can be certain that you are protected for a long time. You might also wonder, how are the flu vaccines different and why are they recommended to be taken yearly. Here the reason is that the flu virus is very special, because it is a little different every year. Remember my last article about the Nobel-winning CRISPR-Cas9 and mutations? It turns out that the flu virus can also undergo some mutations and in this way form new versions of itself over time. So now you are probably already guessing that because the virus mutates and can be slightly different, the antibodies you already have in your organism will not recognize the new, mutated antigens. To make sure that our immune system stays on top of things with regards to the fight against the flu, we should remember to always take our flu vaccine when the flu season is approaching. The flu vaccine is generally a very interesting topic itself, too. If you would like to read in more detail about how these vaccines are developed every year, let me know in the comments!
There are several different types of vaccines
Like I already mentioned, there are several different types of vaccines and these include:
- Live, attenuated vaccines: can fight both viruses and bacteria. They contain the whole, living germs that cause the disease, but in a weakened form (attenuated), so the vaccine itself cannot cause a serious disease. These vaccines are great – because they are so similar the the real infection, they provide amazing immunity without the complications of the real infection. Some of the diseases prevented via this type of vaccine include: measles, mumps, rubella, rotavirus, chickenpox, smallpox.
- Inactivated vaccines: can also fight both viruses and bacteria. These vaccines also contain the whole germs, but in the process of vaccine preparation, the virus or bacteria are killed. Not as strong as the live vaccines, so you might need several doses of these ones. Examples include polio, flu or hepatitis A.
- Toxoid vaccines: used to prevent diseases caused by bacteria that make toxins (or, more simply speaking, poisons). The antibodies here are built against the harmful products of bacteria (toxins), rather than against bacteria themselves. The vaccine itself includes “toxoid”, which is simply a weakened version of that toxin. The DTaP vaccine against Diphtheria and Tetanus is an example here.
- Subunit vaccines and conjugate vaccines: can use a part of the germ, which is enough for the immune system to build the immunity, but not enough to get you ill. They are very specific and build a very strong response. They are so good and safe that can often be used even in people with weakened immunity! A few examples here include: hepatitis B, shingles, Pertussis (or whooping cough) part of the DTaP vaccine.
- mRNA vaccines: you were probably most interested to read about these – the very promising COVID-19 vaccines in the final stages of tests, by Pfizer and Moderna are both mRNA vaccines! Some of these are apparently already on the planes to start distribution! The mRNA vaccine is what I earlier referred to as the modern “blueprint”-containing vaccine, rather than the germ-containing one. What I mean by that is that the vaccine provides a very specific instruction for your body to make the antigen itself. From what we know so far, it looks like we will have to take two doses of these to be safer.
- Recombinant vector vaccines: these have a specific fragment of the genetic material of the virus in them, so that the human body can use it to make these specific parts of the virus. The idea is similar to the mRNA-based vaccines, but the type of information provided for your body is slightly different. AstraZeneca’s and Oxford’s COVID-19 vaccine – if successful – will be a recombinant viral vector-based one.
- DNA vaccines: these are still in the works, but hopefully will be very easy and inexpensive to make, while providing a long-lasting immunity.
Vaccines don’t only include the viruses and bacteria… They also have formaldehyde and mercury derivative! How can that still be good for you?!
Many people who are against vaccines make the argument above to explain why they will not have their children (or themselves) vaccinated. When you look more into all the ingredients that come in a vial of a vaccine you will find a lot of additives. Perhaps the scariest-sounding ones are “thiomersal”, which is a mercury derivative and formaldehyde. For all of you, who might have some reservations about vaccines due to the additives, here is what they are in vaccines for:
Thiomersal – it is in fact a derivative of mercury and we all know that mercury is so dangerous, oh boy! Well, in the thiomersal version it is not as dangerous anymore. Even better! It is actually used to prevent infections, mostly from bacteria and fungus. You will find thiomersal in vaccines, but also for example in tattoo ink. So if you are planning to get an anti-vaccine tattoo because you hate thiomersal, you might be fighting a wrong fight. What is it used for in vaccines, you might ask? It helps make sure that your vaccine does not get contaminated with anything else. So that vicious mercury derivative is in vaccines for a very good reason and in such tiny amounts, that you probably get much more of it in your fish-containing meals.
Formaldehyde – more commonly known as “formalin”, that one is perhaps even scarier! Some of you might know that formaldehyde can be used for embalming dead bodies – it fixes tissue, such that it does not go bad over time. It is also sometimes used in photography, as a stabilizer in one of the final wash steps. In vaccines, it can be added to kill the residual virus or inactivate toxins in the process of manufacturing. The amounts used here are… smaller that what we all already naturally have in us, so again, no need to worry!
If you are interested in getting to know about more chemicals that come with your vaccine, let me know in the comments!
The extra protection we get when others get vaccinated: herd immunity
Finally, some people will say that the immunity naturally built by your body after actually going through a disease is better than what a vaccine gives you. While in some cases it might be true, these diseases can also have very dangerous complications, which we often don’t think about as much as about the immediate symptoms. These complications – let’s not forget – might not only affect the person who got primarily infected, but also their relatives and friends or coworkers, who might have gotten infected from them. So when you are vaccinated, you are very likely to get good protection.
However, not everyone can get vaccinated and I am not talking about choosing to get vaccinated, but actually not being able to do so. The reasons can include: a weak immune system (for example cancer patients), allergies to some of the vaccine components, or simply being too young to get vaccinated. Such people can still be protected, as long as they live in communities where other people are vaccinated – nobody around to get sick from. Think of it as making a nice protective umbrella over others, through your own vaccination. I’d like to make another movie analogy here, with “Twilight” and Bella’s protective shield… But you might think it’s too much by now, so I won’t. Instead, here is a better illustration of what I mean, straight from the WHO website:
So with all this new (or maybe old to some of you), knowledge – what do you think? Will you get vaccinated against COVID-19 when a vaccine is available? Let me know in the comments below or on social media.
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I would like to acknowledge Tony Vega for his help with editing work for this post.
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Since this time I am not only giving you a textbook knowledge, but also some extras, I thought it is important that I provide the sources outside of my own brain, which I used in preparation of this article:
– “Molecular Biology of the Cell”, 4th edition – Alberts B, Johnson A, Lewis J, et al.New York: Garland Science; 2002; chapter: “Lymphocytes and the Cellular Basis of Adaptive Immunity”
– WHO website – How do vaccines work?
– CDC website – Vaccines and Immunizations
– CDC “Understanding how vaccines work”
– Vaccines.gov
– AOL article about COVID-19 vaccine distribution
– Oxford’s information page about their COVID-19 vaccine
– Moderna’s COVID-19 vaccine website
– Pfizer’s COVID-19 updates website
– AstraZeneca’s COVID-19 information hub
– PublicHealth.org website
– British Society for Immunology
– Updates to COVID-19 Immunity and Epidemiology to Inform Vaccine Policy
Martyna Scribbles 
One of the most notable concerns regarding the covid vaccine is the lack of time needed to observe the possibility of deleterious sequelae (possibly stemming from the infamous rushed swine flu vaccine). How long would it take to determine the chance of such is negligible? Are specific vaccine types more prone to causing complications? What causes them in the first place?
Is the use of phrase “herd immunity” incorrect when it comes to the “strategy” of letting communities be infected in order to gain natural immunity to the disease (chicken pox could possibly be an example why it is the case)? Does vaccine-derived immunity last longer?
Thank you for your comment! These are all very valid questions.
1) As for the safety of the new vaccines as compared to the rushed swine flu vaccine of 1976, I like to think that science and medicine are far more advanced by now. That being said, with this particular experience in mind, the companies will surely make every effort not to endanger the people again. Additionally, the vaccines that are being developed now are not exactly fast-tracked, like the old swine flu one was. These vaccines are going through all the necessary testing processes that are required and unlike the swine flu vaccine, these cannot “borrow” from previously developed ones, simply because this virus is too different. All this does not mean that there will not be any side effects of the vaccines. It actually seems that there are already some reports of potentially some more bothering early side effects than with many other vaccinations. But I believe that as long as a patient is aware of these potential side effects and they monitor their body well for the first 24 hours or so, such side effects should be bearable and not really threatening to the patient. We will see what FDA says about the vaccines that have been developed so far! I am very curious myself to watch this in process.
2) Your question about herd immunity is also a very good one! Thank you for pointing this out. A concept of developing a herd immunity because the majority of the society will have gone through a disease and therefore become immune does not always work, simply because the immunity to different diseases lasts for a different amount of time. So with chickenpox for example, once you get sick, you are good for life, because the antibodies formed in your immune system and the memory cells will be there for a very long time. When we talk about the common cold on the other hand, you don’t get long lasting immunity and that’s why you can get it more than once even in one winter season. When someone goes through the COVID infection, the amount of the specific antibodies significantly decreases already after two months. So after that time the specific immunity wears off and the same patients can become infected again. So in this case the herd immunity would not work, even if everyone got infected. As to whether the vaccine-based immunity will or will not last longer – I simply don’t know. But it does seem like the antibodies are longer-lived in patients who have gone through the infection more than once, so I really hope that the second dose that Moderna and Pfizer are proposing will in fact cause the immunity to be long-lasting. Let’s wait for the FDA to give their opinion!
I hope that answers your questions. Thank you again!