Investigating Vaccines: How does the COVID Vaccine Work?
Ever since quarantine started, 2020 has been a year spotlighting the field of immunology, and we need to understand and apply it more than ever. The body is constantly in contact with pathogens and luckily our immune system is powerful enough to prevent and attack foreign bodies without it escalating most of the time. Since it is extremely detailed and precise in its mechanisms, the complexity of studying the immune system means that there is still a lot to grasp and understand.
There are two subsets of the immune system, innate and adaptive. The innate immune system comprises cells that have no “memory” of pathogens and attack spontaneously when a foreign body enters the body and is the first to defend the body with the main goal of eradicating them. Examples of these cells include natural killer cells, macrophages, and neutrophils. Adaptive immunity means that there are cells designed to recognize a specific antigen in the body and are trained to attack it anytime it enters the body, rather than any antigen. An antigen is a marker that is outside of a molecule that can bind to receptors of immune cells. Antigens are usually a threat to the body since they are not recognized as part of that person’s body. For instance, when looking at blood types the blood type that you have describes the antigen that is present outside of the blood cell. If somebody has B+ blood, they can only accept B+ blood because that antigen is not foreign. However, that person can accept O blood as well because there is no antigen present on the outside of that red blood cell, so the immune system will not detect anything foreign which is why it is considered the “universal donor”. Similarly, one of the main contributors to the adaptive immune system are blood proteins called antibodies, or immunoglobulins.
Antibodies are Y-shaped proteins that are able to bind to specific antigens to trigger an immune response. When the bodies are introduced to a pathogen for the first time, immune cells called B-cells secrete antibodies that will bind to the antigen. There are five main immunoglobulin classes, and IgG is the main class that creates a primary and secondary response. The first exposure and reaction to an antigen takes time and will likely yield symptoms that are similar to an allergy. If the same antigen were to enter the body for the second time, the antibodies have essentially remembered this antigen and are trained to attack it which means the immune response will occur much quicker than the first time. There are a couple ways in which antibodies can tackle an antigen, for instance releasing toxins to counteract the harm from the pathogen, form clumps so that the antigens can be ingested by macrophages, and other procedures.
Similarly, vaccines use this same tactic to give immunity for a particular disease. There are many methods to how a vaccine can be created, but the most common “adjuvant”, or ingredient of the vaccine is a deactivated virus or strain of a disease. This virus will enter the body but since it is killed or engineered, it will not harm the body but rather allow immune cells to produce antibodies for this virus. Likewise, if a person were to come into contact with the actual virus, the body is already prepared and immune to defeat it.
Fast forward to this pandemic, COVID-19 is a derivative of the family of SARS-CoV-2 viruses. Viruses contain genetic material encased by a protein shell that must enter a host cell to replicate the genes. The COVID-19 virus has single stranded RNA as the genetic material and on the outer part of the protein contains a glycoprotein called a “spike” protein. This is the major target for the vaccines. There are at least 6 major pharmaceutical companies that are creating the COVID-19 vaccine and are in the midst of clinical trials to prepare for the administration of the vaccine. Pfizer/BioNTech and Moderna both use messenger RNA that is the same sequence present in the virus, as the main ingredient in the vaccine that will allow cells in the body to read it and create the spike protein which will then be recognized as foreign by immune cells, so that they are ready in the case that the actual COVID virus is contracted.
AstraZeneca and Johnson&Johnson both use a slightly different method by inserting genetically engineered adenoviruses to get the cells to produce the spike proteins. Adenoviruses are a family of viruses that are relatively harmless and only produce common cold symptoms. Unlike Pfizer and Moderna using mRNA, these companies insert DNA sequences that contain the genes for the spike protein. The genetic material from the adenovirus itself is removed so those effects do not occur in the body at the same time. Once the adenovirus enters the cells, the genes turn into mRNA and finally turn into the spike protein and thus antibodies are prepared. These descriptions are just a brief overview of the methods used, because there are detailed variations between each company’s approach to the vaccine.
Iffah Shaikh is currently in her first year at McMaster university, enrolled in the Bachelor of Health Sciences program. She lives in Cambridge, ON, but grew up in Oakville and Milton. She aspires to go to medical school, and become an ER doctor or a specialist of some sort in the future. Her past-times are going outside and playing sports or bike riding, watching Netflix, reading books, and making videos and memes of her friends. Some new hobbies she wants to try and start doing more of is trying out new makeup looks, cooking new dishes, and drawing.
