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The Beginners Guide to COVID-19 mRNA Vaccines

Aug 24, 2021 10:30:00 AM / by Nancy Andon, MSc

AdobeStock_407610791-1Part 2: How COVID-19 mRNA Vaccines Trigger Immunity

In Part 1 of our blog series, we described what an mRNA vaccine is, and how it works.

In Part 2, we will explain how receiving the mRNA COVID-19 vaccine triggers the human immune system to start producing antibodies and facilitates long-term protection.

HemaCare strongly believes in supporting the next generation of young scientists and professionals through community outreach and educational opportunities. As a special feature of this blog series, we are sharing the hand-drawn illustrations of Arya Krishnan, a young grade-schooler excited to share his understanding of the vaccine with others.

The first part of this series introduced mRNA vaccines and explained how COVID-19 mRNA vaccines work. Briefly, the vaccine is basically a set of instructions for a harmless version of the SARS-CoV2 spike protein. Our cells translate those instructions and produce the protein. But how is a little piece of protein transformed into a full-blown immune response?

The answer lies in the different types of cells that are part of the human immune system. Certain immune cells are specialized to recognize pathogens (in this case, the piece of spike protein) as invasive. Once recognized, antigen-presenting cells like dendritic cells will display a fragment of the pathogen on their cell surface as something to be recognized and defended against. Dendritic cells displaying the modified spike protein will interact with and activate other immune cells called “killer” T cells and “helper” T cells (See Fig. 1).

Part 2 Blog Image

Once activated, “helper” T cells do a number of things. They release chemical signals that cause other immune cells to proliferate and differentiate, amplifying the immune response. They also activate “killer” T cells, which directly attack infected cells, and B cells, which make antibodies. Antibodies are used to tag cells infected with the recognized pathogen, in this case, the SARS-CoV-2 spike protein.

Some B cells, known as memory B cells, can be extremely long-lived. Memory B cells made in response to the COVID-19 mRNA vaccine will become activated if the spike protein is ever encountered again in the future. This means if a vaccinated person is exposed to COVID-19, their body should recognize the spike protein and immediately launch an immune response. Memory B cells will rapidly produce antibodies, triggering an immune response that protects their host from that pathogen. This is how vaccines can give us long-term immunity to a disease.

As mentioned previously, the body’s immune response to COVID-19 is different than its response to the vaccine. The SARS-CoV-2 virus attacks and infects cells, reproducing and spreading rapidly. It can cause inflammation, especially in vulnerable tissues like the lungs. In some cases, severe inflammation can result in an out-of-control immune response, which can be deadly.

The COVID-19 vaccine triggers the immune system, but there is no viral infection and minimal inflammation. In rare cases, the vaccine can cause unpleasant or even life-threatening side effects, but for the vast majority of people there is little or no adverse reaction.

HemaCare and its partners at Cellero supply a comprehensive array of COVID-19 related products to help scientists investigate all facets of the disease, from diagnostics to therapeutics and vaccine development. Plasma, serum, and PBMCs from recovered COVID-19 patients can be purchased on our website. Customers can also purchase a T cell line specific for the spike protein from SARS-CoV-2 and COVID-19 vaccinated PBMCs, plasma, and serum.

If you would like to learn more, please visit our website and browse our selection of COVID-19 related products and services.


Topics: PBMCs, Serum, T Cells, Plasma

Nancy Andon, MSc

Written by Nancy Andon, MSc

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