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What are the two vaccines, and what are they made of?
The two COVID-19 vaccines approved for emergency use in Canada are the ones manufactured by Pfizer-BioNTech and by Moderna. Both vaccines induce our immune system to produce antibodies that can bind to a protein on the surface of the virus that causes COVID-19. This protein is called the ‘Spike’ protein and its main function is to attached to the surface of a cell and allow entry of the virus into the cells to start an infection. The antibodies interfere with the entry of the virus into the cells, thereby, preventing infection.
The main component of both vaccines is the instruction code in the form of an mRNA molecule that directs the cells in our body to produce the ‘Spike’ protein of the virus. The vaccine does not contain the virus, so it does not cause an infection. After synthesis of the ‘Spike’ protein, the mRNA is degraded in the cells. Our immune system will then recognize the ‘Spike’ protein and produce antibodies against it. These antibodies will protect us against infection by the virus.
How do the vaccines work?
Vaccines work by training our immune system to recognize and react against an infectious agent without causing an infection. In the case of COVID-19, the infectious agent is the SARS-CoV-2 virus. The COVID-19 vaccines train our immune system to react against the ‘Spike’ protein of SARS-CoV-2. This relies on two fundamental properties of our immune system. One is its ability to distinguish between ‘self’-proteins from the body and ‘foreign’-proteins from outside the body – our immune system only reacts against foreign-proteins, in this case the ‘Spike’ protein of SARS-CoV-2 virus. Second is its ability to form a memory of that response. The vaccines induce our immune system to recognize and produce antibodies against the ‘Spike’ protein of SARS-CoV-2 virus, so that, if we get exposed to the virus our immune system remembers and knows how to react against the ‘Spike’ protein of the virus, and we have the antibodies to fight the infection.
I have heard the term mRNA. What does that mean? How is it different than other types of vaccines?
The mRNA or messenger RNA is a molecule that carries the instruction code for the synthesis of a protein in a cells. Our genes are made of DNA, which contains the blue print for our cells to make proteins. This DNA genetic code first gets copied into mRNA molecules and then the code on mRNA is used to make proteins. To make the COVID-19 vaccines, scientists sequenced the whole genome of SARS-CoV-2 virus and identified the genetic blue print for the virus’ ‘Spike’ protein. They then made mRNA molecules containing this genetic code. The vaccine preparation delivers these mRNA molecules into our body that will instruct our cells to make the ‘Spike’ protein, which are then recognized by our immune system to make antibodies against it.
mRNA vaccines are different from other types of vaccines in that they do not contain the virus or parts of the virus in the vaccine preparation. Other vaccine types contain dead or inactivated virus, or proteins from the virus to induce the immune system to recognize and react against the virus proteins. The mRNA vaccines contain the instructions for how to make the virus protein in the body, so they do not contain any part of the virus, which can add to their safety.
About the Expert:
Dr. Mir Munir Rahim is an Assistant Professor in the Department of Biomedical Sciences at the University of Windsor. He completed his Ph.D. in Experimental Medicine at McGill University in Montreal, Quebec, his M.Sc in Biology from the Department of Biology, Concordia University, Montreal, Quebec and his Masters of Science in Microbiology from the University of Delhi in New Delhi, India. Read more.