What’s Special About the New COVID-19 Vaccines?
Medical staff distributing COVID-19 vaccines (Joe_McUbed, iStockphoto)
Medical staff distributing COVID-19 vaccines (Joe_McUbed, iStockphoto)
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Learn about viruses, vaccines and why the new COVID-19 vaccines are innovative.
Have you ever wondered what’s in a vaccine and how it helps prevent infection? Maybe you’ve heard that the new COVID-19 vaccine is different from typical vaccines? Well, it turns out that scientists have many options when making a vaccine. To understand these options and why the new COVID-19 vaccine is unique, we first need to know how viruses interact with the various immune cells in our body.
What’s in a virus?
Viruses are made of genetic material (either DNA or RNA) and proteins. The genetic material serves as a “blueprint” to make the proteins. Some proteins surround the genetic material and form the structure of the virus. Other proteins help the virus survive and make more copies of itself. One such protein is a receptor protein. Viruses use this "spikey" protein to attach itself to cells in our body.
Once attached, viruses can insert their genetic material into our cells. Their genetic material takes over our own protein-making machinery. It makes copies of its own genetic material and builds its own proteins. It even uses our own cells to assemble more viruses!
Our Immune Response to Viruses
Our cells also contain genetic material. And like viruses, our cells make proteins that do different jobs. The main job of our immune system is to keep an eye on the health of our cells. One way they do this is by “scanning” the surface of cells for molecules called antigens. Antigens provide information to your immune system. They act like identification tags. Healthy cells have 'self-antigens' on their surfaces. These ‘self-antigens’ let the immune system know that they are not intruders.
Infected cells have pieces of viral antigens on their surfaces. Cytotoxic or "Killer" T cells look for these antigens as they scan the surface of cells. If they have viral antigens on a cell, they know that the cell does not belong. They attack the cell and kill it to prevent the formation of any more viruses, hence their name.
Another monitoring system involves specialized immune cells called Antigen-Presenting Cells (APCs). Once these cells have come into contact with viral antigens, the antigens appear on their surface. These antigens can activate another “scanning” T cell, the Helper T cell. Activated T helper cells will start sending out signals to other immune cells. This will bring over other cells, such as more Killer T cells.
An APC can also attach proteins to its surface to activate immune cells called B cells. Scientists call this "presenting" the protein. If a B cell detects a viral protein and receives messages from the Helper T cells, it will start making antiviral proteins called antibodies. Antibodies are specialized proteins that can bind to a virus. We call antibodies that prevent viruses from infecting new cells neutralizing antibodies.
To help our bodies fight viruses, scientists develop vaccines. The goal of a vaccine is to use parts of the virus to trigger an immune response without actually making you sick. There are several different ways that this can be done.
Types of Vaccines
Scientists can make vaccines from whole viruses or parts of viruses. These include:
1) Inactivated Viruses
For these vaccines, scientists take a virus and kill it with chemicals or UV light. It still has its proteins, but its genetic material can no longer make more viruses. We call this type of virus inactivated. The inactivated virus is injected into the body. APCs bind to the virus and activate B cells. One type of APC called dendritic cells can also gobble up the dead virus. These cells will then present digested viral proteins to activate Helper T cells. Using inactivated viruses results in a long-lasting antibody immune response. This means that if your immune system is exposed to a live version of the same virus it will quickly use neutralizing antibodies to keep you from getting sick. The Rabies vaccine is an example of an inactivated virus vaccine.
2) Attenuated Viruses
These vaccines use viruses that are still alive, but have been changed so that they cannot make you seriously ill. We call these attenuated or weakened viruses. They still have all the proteins and peptides needed to stimulate your immune system. The viral proteins stimulate B cells and also get displayed by APCs. This results in strong antibody protection. In some cases, our cells will use the virus’ genetic material to produce peptides that activate our Killer T cells. The measles vaccine uses a weakened virus.
3) Subunits
For these vaccines, scientists produce a protein specific to a virus rather than using the entire virus. Since it is only a part of a virus, scientists call this a subunit. They often use a surface protein that the virus needs to infect cells. APCs present the subunit to B cells and helper T cells. Like inactivated viruses, subunits produce long-lasting neutralizing antibodies. An example of a subunit vaccine is the Hepatitis B vaccine.
4) Vector-based Vaccines
For these vaccines, scientists use a piece of genetic material from the virus of interest. They then “cut and paste” it into a safe virus that can’t make you sick. The safe virus injects the genetic material into cells, where it’s used to produce viral proteins and peptides. This stimulates B cells to make antibodies, as well as Helper T cells and Killer T cells. Scientists have developed a vector-based vaccine for the Ebola virus.
5) DNA
For these vaccines, scientists remove specific genetic sequences from the DNA of a virus. They then place it into a 'delivery system' called a plasmid. A plasmid is a small, circular, double-stranded DNA molecule. It exists apart from a cell's chromosomal DNA. The DNA of bacteria exists as plasmids. Cells that take up the DNA plasmid will use their own protein-making machinery to produce a particular viral protein. The viral protein and associated peptides can cause an immune response from Killer T cells, T helper cells, and B cells. There are currently no DNA vaccines for humans. But veterinarians use a DNA vaccine to protect horses from the West Nile virus.
6) mRNA
For these vaccines, messenger RNA (mRNA) is used to produce viral proteins and peptides. Scientists package the mRNA inside a special delivery system called lipid nanoparticles (LNPs). LNPs are tiny spheres made out of lipids. Lipids are molecules that do not interact with water, and can protect the mRNA vaccine from being destroyed before it’s delivered to cells. When an LNP interacts with a cell, the cell engulfs it. Once the mRNA is inside the cell, the protein-making machinery the cell uses the RNA to make viral proteins and peptides. The viral proteins will stimulate B cells to make neutralizing antibodies to prevent viral infection and the peptides may activate helper T cells and killer T cells. Several COVID-19 vaccines use mRNA.
COVID-19 Vaccines
The new COVID-19 vaccines are the only vaccines currently approved for use in humans that use mRNA. They are also unique because their development was very fast. Only 8 months after the pandemic was declared in March 2020, the first successful phase 3 trial of an mRNA-based COVID-19 vaccine candidate was announced. Normally it takes years to develop a new vaccine. The quickest vaccine developed before now was for the mumps. It took four years to develop. Scientists were able to develop the COVID-19 vaccines so quickly because the need for them was so great. And they were not alone - it was a global effort.
Some people have expressed concern that it may have been done too fast. But it’s important to note that each vaccine had to go through all the normal safety steps for approval and many volunteered to be part of the clinical trials to test these vaccines.
In Canada, as of March 2021, authorized vaccines are available from three manufacturers:
- Moderna (mRNA)
- Pfizer-BioNTech (mRNA)
- AstraZeneca (vector-based)
As you hear about more people getting the COVID-19 vaccine, remember the exciting science that made it possible!
Let’s Talk Science appreciates the work and contributions of Catherine Ewen, PhD., Senior Scientist, STEMCELL Technologies in the development of this article.
About STEMCELL Technologies
STEMCELL Technologies is Canada’s largest biotechnology company. Based in Vancouver, STEMCELL supports life sciences research around the world with more than 2,500 specialized reagents, tools, and services. STEMCELL offers high-quality cell culture media, cell separation technologies, instruments, accessory products, and educational resources that are used by scientists advancing the stem cell, immunology, cancer, regenerative medicine, microbiology, and cellular therapy fields.
Find more information at www.stemcell.com
Starting Points
- Have you, or someone close to you, tested positive for COVID-19? How did it make you feel?
- How do you feel about getting a COVID-19 vaccine? Do you have any concerns? If so, what are they?
- Do you have a preference for which vaccine you get? Why or why not?
Do you feel that the vaccine testing should have been “fast-tracked” as it was, or should it have followed a more typical timeline for development? Explain.
- Compare and contrast Killer T cells, Helper T cells and B cells.
- How are mRNA vaccines similar to and different from other types of vaccines?
- How confident should Canadians be about the COVID-19 vaccines available to us? Do you think that enough testing has been done? Explain.
- Has the process of developing a COVID-19 vaccine differed from other vaccines?
- Where do you get your information about COVID-19 and vaccinations?
- What do you consider to be trustworthy sources of information about COVID-19 and vaccinations?
- This article supports teaching and learning of biology, biotechnology and health related to viruses, vaccination, proteins, the immune system and public health. Concepts introduced include Cytotoxic or "Killer" T cells, Antigen-Presenting Cells (APC)s, Inactivated Viruses, Subunits, Attenuated Viruses, Vector-based Vaccines and lipid nanoparticles (LNPs).
- To discuss the implications of fast-tracking vaccines to market, students could participate in a Think-Discuss-Decide Learning Strategy. Ready-to-use reproducibles for this learning strategy are available in [Google Doc] and [PDF] formats.
Connecting and Relating
- Have you, or someone close to you, tested positive for COVID-19? How did it make you feel?
- How do you feel about getting a COVID-19 vaccine? Do you have any concerns? If so, what are they?
- Do you have a preference for which vaccine you get? Why or why not?
Relating Science and Technology to Society and the Environment
Do you feel that the vaccine testing should have been “fast-tracked” as it was, or should it have followed a more typical timeline for development? Explain.
Exploring Concepts
- Compare and contrast Killer T cells, Helper T cells and B cells.
- How are mRNA vaccines similar to and different from other types of vaccines?
Nature of Science/Nature of Technology
- How confident should Canadians be about the COVID-19 vaccines available to us? Do you think that enough testing has been done? Explain.
- Has the process of developing a COVID-19 vaccine differed from other vaccines?
Media Literacy
- Where do you get your information about COVID-19 and vaccinations?
- What do you consider to be trustworthy sources of information about COVID-19 and vaccinations?
Teaching Suggestions
- This article supports teaching and learning of biology, biotechnology and health related to viruses, vaccination, proteins, the immune system and public health. Concepts introduced include Cytotoxic or "Killer" T cells, Antigen-Presenting Cells (APC)s, Inactivated Viruses, Subunits, Attenuated Viruses, Vector-based Vaccines and lipid nanoparticles (LNPs).
- To discuss the implications of fast-tracking vaccines to market, students could participate in a Think-Discuss-Decide Learning Strategy. Ready-to-use reproducibles for this learning strategy are available in [Google Doc] and [PDF] formats.
References
Branswell, H. (2020, Dec. 2). The Covid-19 vaccines are a marvel of science. Here’s how we can make the best use of them. STAT.
Callaway, E. (2020, April 28). The race for coronavirus vaccines: a graphical guide. Nature.
Catalyst University. (2019). Basics of Antigen Presentation.
Centers for Disease Control and Prevention. (2020, Dec. 18). Understanding mRNA COVID-19 Vaccines.
Fischetti, M. (n.d.). Inside the Coronavirus: What scientists know about the inner workings of the pathogen that has infected the world. Scientific American.
Ramesh, R. (n.d.). Types of Vaccines Infographics . Covid Response Corps.