What’s Special About the New COVID-19 Vaccines?

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:

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