How Do mRNA Vaccines Work? Explained by Dr. Guenther, MD

What is Messenger RNA?

Messenger RNA (mRNA) is a single strand of coded material instructing cells to produce specific proteins. The COVID-19 vaccines made by Pfizer/Biontic and Moderna use mRNA to create immunity without infecting our bodies’ cells.

rna vaccine

How Do mRNA Vaccines Work?

These vaccines contain mRNA that carries the code for the COVID-19 virus “spike” proteins. The mRNA is coated with a tiny fat layer that specifically attracts immune cells in our body to ingest them.

Once the mRNA is ingested into the cell, the fatty layer is dissolved, and the machinery of the cell reads the mRNA and produces the “spike” protein.

That protein then moves to the cell’s surface, and other white blood cells (lymphocytes) are alerted that these proteins are foreign to us and develop antibodies to the “spike” protein.

These antibodies are then produced in vast quantities and bind to any of these proteins. If we are infected by the COIVD-19 virus, these antibodies are ready to attack the virus’ spike proteins and prevent the virus from infecting our cells.


Does the mRNA enter our cells’ nucleus where our genes are stored?

No. The mRNA stays in the cells’ cytoplasm, where proteins are made. They never enter the nucleus of our white blood cells and therefore can’s affect our genes.

Does mRNA enter cells throughout our body?

No. The only cells that ingest the “spike” proteins are Dendritic Cells which are part of our white blood cell system.

Can these “spike” proteins cause COVID infection?

No. The spike protein is one small part of the COVID-19 virus and can’t lead to infection. Our body’s response to the development of antibodies to the “spike” protein can cause symptoms such as headaches, body aches, low fevers, tiredness.

Why is the Pfizer/Biontec the only vaccine approved for children?

At this point in time, the Pfizer/Biontec vaccine has accumulated the most information of response to the vaccine. This came about because Israel agreed to use the Pfizer vaccine and follow the health of all people in the country who received the vaccine. Other vaccines distributed their vaccines in various countries with differing abilities to monitor everyone who received the vaccine. Thus, Pfizer had more information earlier than other companies that produced different vaccines. Over time, these other vaccines will have enough information for our FDA to thoroughly evaluate those vaccines’ effectiveness.

Can the mRNA vaccines affect fertility?

No. Since the mRNA only enters one specific type of white blood cell, it can’t affect the eggs in our ovaries or the sperm in our testes.

Is the vaccine safe for pregnant women?

Yes. The CDC and FDA strongly recommend that pregnant women receive the COVID-19 vaccines. There is strong evidence that pregnant women and their unborn children infected by the COVID virus are at higher risk for serious complications including death. The rate of stillborn births in women infected by COVID-19 is much higher than previously anticipated.


If you have questions that weren’t answered, please feel free to contact us. We want families to have all the answers they need!


About Dr. Guenther

Dr. John Guenther joined The Youth Clinic in 1989. He is a native of Denver and graduated from medical school at the University of Colorado. He completed his pediatric residency at Brown University in Rhode Island. Dr. Guenther is Board Certified and a fellow of the American Academy of Pediatrics.

dr. john guenther

Covid-19 Vaccines at The Youth Clinic

In anticipation of the PFIZER Covid vaccine being approved for ages 5 and above, we are planning COVID Vaccination Clinics the first week of November. These COVID Vaccine Clinics are open to both Youth Clinic patients and the community.

At this time, the vaccine clinic is currently in planning. As soon as the vaccines are available and appointments are able to be scheduled we will contact patients via email and text. 

We understand that you may have questions about receiving the COVID vaccination. For accurate information about the vaccine, please visit the CDC FAQ page by clicking this link.