Hope for 2021 - Science Behind Covid-19 Vaccine
Author: Arlene Vinion Dubiel
The first case of Covid-19 in the United States was diagnosed on January 20, 2020. Less than a year later, thousands of healthcare workers and others have been vaccinated for this novel virus with many more vaccinations to come. With all the talk about the pandemic and the quick rollout of vaccinations, there has been misinformation making it difficult to identify the facts.
My intent with this blog is to share those facts about the Covid-19 vaccine and how your body may react to it. Along the way, we talk about molecular biology, cell biology, and immunology. I can guarantee that the information is accurate and uses reputable sources. I also hope it is written in such a way that high school and college biology students can understand.
How do vaccines work?
In general terms, vaccines encourage your body to mount an immune response to an infectious agent that you may become exposed to at a later time. If your body mounts an immune response, then when it encounters this infectious agent, your body will be able to fight it off quickly and you will be less likely to get sick.
The first vaccine was tested by Edward Jenner in 1796 against smallpox. Smallpox was a devastating disease killing 3 in 10 people and leaving survivors with scars from the skin pustules that were a hallmark of the infection. Milkmaids who had contracted cowpox, as evidence from the pustules on their hands, did not get smallpox. Edward Jenner took some of the material from a cowpox sore and injected it into the 9-year-old son of his gardener, James Phipps. He then repeatedly exposed James to the smallpox virus, but the boy never did contract smallpox. Despite the ethical issues of this experiment, it did work and Jenner published the results of his study in 1801. People around the world began to be vaccinated against smallpox using the related but non-deadly cowpox virus. If you have never heard of smallpox, it’s because it no longer exists in nature. The World Health Assembly declared smallpox eradicated in 1980.
We are now vaccinated against many different infectious agents to the improved health of humans overall. Current vaccines take different forms. Some use the whole infectious agent, but the agent is weak (live-attenuated) or killed so an infection will not occur. The original smallpox vaccine is akin to a live-attenuated virus. Other vaccines use unique components of an infectious agent like a protein or polysaccharide. There is NO chance that someone could get the disease from these types of vaccines which use the names subunit, recombinant, or conjugant. The downside is that you often need a booster shot to ensure ongoing protection. The new Covid-19 vaccines are akin to these latter vaccines where there is NO chance of catching Covid-19 from getting the vaccine.
What is in the Covid-19 vaccine?
The current Covid-19 vaccines from both Pfizer-BioNTech and Moderna both use mRNA, also called messenger RNA, as the active component. The Pfizer vaccine has three additional components: sucrose (sugar), salts, and lipids. The salts and sucrose are basic molecules that keep the active component of the vaccine stable both outside and inside your body. Lipids, commonly called fats, pay a unique role in the vaccine. They allow the active component, the mRNA, to get inside of your cells. The cell membrane is made up of lipids, so the lipids in the vaccine, with the mRNA,can pass through the cell membrane into the interior of the cell.
Once the mRNA gets into your cell, it can encounter ribosomes. Your cell’s ribosomes have one simple function, to find mRNA and translate it into proteins. It does not matter whether the mRNA comes from a vaccine, a virus, or your own cells, ribosomes will make protein from mRNA. The vaccine’s mRNA molecule encodes for the Covid-19 spike protein - the spikes on the surface of the virus. This spike protein goes to the surface of the cells that have made it. That is when your immune system takes over. Components of your immune system see the spike protein, realizes that the protein is not supposed to be there, and begins mounting a response.
There are a couple of points to make before we talk about the immune response. First, your body is near perfect at recycling and reusing materials. The sugar and salts in the vaccine get used by your body's cells as needed. The lipids likewise are broken down or recycled and used as needed. mRNA gets broken down very quickly in your cells. Breaking apart mRNA molecules is how the cell naturally controls for the amount of protein that is made. Once the mRNA is broken up, the ribosomes can no longer make spike protein. All this means that within a couple hours, the components from the vaccine are recycled or destroyed by your body.
There have been reports of people having an allergic reaction to the vaccine. This is extremely rare, but it does happen. Some people have an allergy to polyethylene glycol (PEG) which is one of the lipids in the vaccine. For people who are allergic to PEG, their body’s immune system has already encountered PEG and has immune system components prepared to react to it. The immune system thinks that PEG is dangerous and will immediately mount a large reaction - trying to get PEG out of the body as quickly as possible. An allergic reaction would happen within an hour of receiving the vaccine with symptoms of difficulty breathing, rash, and rapid heartbeat. Again, this is very rare and medical professionals are aware and prepared should an allergic reaction occur.
Our savior: the immune system
The immune system is a complicated set of many different components working together to do one thing: protect the body. When your immune system sees something in your body that appears to be a danger, it will fight back - very hard, very fast. When you scrape your skin, it immediately becomes red and swollen. This is your immune system at work, flooding the area with plasma and cells to destroy anything that could possibly harm the body.
Your skin is your body’s first line of defense. As soon as the vaccine shot pierces your skin, your immune system recognizes that there could be a danger, so starts to flood the immediate area with plasma and cells. Shortly thereafter after, the mRNA gets into your cells with the help of the vaccine lipid and your cells start to produce the Covid-19 spike protein. The immune cells that are already there see this spike protein and recognize that this is something new and something potentially dangerous because it came in with the shot.
It is at this point, when the immune system sees the spike protein as dangerous, that it gets to work, going through a multi-step process to help immunize your body against this protein by making antibodies. I will not go into the details of how that works here as it is a topic suited for a college-level immunology course. If you would like the short version, The College of Physicians of Philadelphia have an interactive resource, How Vaccines Work, that explains the components of the immune system, including the antibody-producing B-cells, and how they all work together to give your body long-term immunity and protection against infectious agents.
Antibodies are large Y-shaped proteins produced by B-cells that circulate in the blood. Antibodies and B-cells are very specific, each one recognizing a very small, specific part of a molecule. After receiving the Covid-19 vaccine, you will have antibodies to the spike protein. If you ever encounter the spike protein again, like if you were exposed directly to the virus, then the B-cells will grow and divide and produce antibodies that can stick to the spike protein and stop it from working. This can happen quickly because the vaccine prepared your immune system to attack much faster and much stronger than the first time your body may have encountered the spike protein. To ensure that your body has produced enough B-cells and antibodies that can be effective against the Covid-19 spike protein, a second vaccination is necessary.
Taking a step back, you have likely heard that there are two Covid-19 tests. One, with the nasal swab, looks for the presence of the virus itself to see if you currently have an infection. The other tests a sample of your blood to see if there are antibodies. If you have been exposed to the virus, or if you have received the vaccine, you will have antibodies in your bloodstream. It is these antibodies that will protect you from getting sick from the virus.
Vaccine facts and misinformation
“The Covid-19 vaccine is one of the safest and simplest vaccines you could possibly receive.”
The information above explains why it is not possible to become infected with Covid-19 from the vaccine - you are not being exposed to the virus. But you may have some side effects from receiving the vaccine. The most common is injection site pain, redness, and/or swelling. This is very typical and makes sense if you know that your immune system immediately floods any area of body damage with plasma and immune cells. The immune system is looking for anything that could be dangerous to your body.
Other side effects from the vaccine include tiredness, headache, or fever and happen more commonly after the second dose. These side effects can be explained as your immune system functioning as it should. Your immune system likely made some B-cells and antibodies with the first shot and these become activated with the second shot. Most of the time you get sick from an infection like a cold virus or the flu, it is not the infectious agent itself that is making you feel bad, it is your body’s immune system trying to fight off that infectious agent that makes you feel bad. Fever, headache, and tiredness are common indicators of your immune system working as it should.
If someone does get sick from Covid-19 after receiving the vaccine, it is NOT from the vaccine itself. Rather it is because they were exposed to the virus itself before the body developed an adequate immune response. This would more likely happen before receiving the second dose of the vaccine. The body not mounting an adequate immune response explains the approximately 5% of people who receive the vaccine and yet still get sick with the virus.
In less than a month of the first Covid-19 vaccine being approved by the Food and Drug Administration (FDA), hundreds of thousands of health care workers, first responders, and others were vaccinated. This very quick turn around time is easily explained by the simplicity of the vaccine. Vaccine components of sugar, salt, and lipids are readily available. The mRNA can also be created quickly and easily from simple components using machines in a laboratory. The difficult part is not in producing the vaccine, but in packaging and delivering the vaccine.
Bottom line, the Covid-19 vaccine is one of the safest and simplest vaccines you could possibly receive. The vaccine uses your own cell’s systems to make the Covid-19 spike protein. Then it lets your immune system do its work to make antibodies to the spike protein. As long as you do not have an allergy to any of the vaccine components, you will have few to no side effects.
I’m not a healthcare worker. I am not in any high risk groups. But I will very happily receive the Covid-19 vaccine when I’m allowed to get it. Better to be safe and prepare your immune system when you are healthier with a vaccine than risk getting an infection later.
For more information, the full fact sheet is available as a pdf from the Food and Drug Administration (FDA) here.
Knowledge is power. Get the Covid-19 vaccine without fear and let this pandemic end so we can be together in 2021.
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