Skip to main content

mRNA Vaccination Technology to Prevent COVID-19

Pharmaceutical companies, such as Pfizer (jointly with BioNTech) and Moderna, have created effective new vaccines that rely on genetic material called messenger RNA (mRNA) to prevent people from getting ill from COVID-19.

Scientists have been researching and working with mRNA vaccine technology for decades. However, the COVID-19 pandemic gave them the unique opportunity to put their knowledge and tools to the test and develop the first working mRNA vaccine. The Pfizer/BioNTech and Moderna mRNA vaccines are the first two COVID-19 vaccines authorized for use in the United States. 

Despite the quick turnaround for these vaccines, they are still being held to the same rigorous standards for safety and efficacy. We break down how it works, its effectiveness, and more to help you decide if the mRNA vaccine is right for you and your loved ones.


What Is an mRNA Vaccine?

Many traditional vaccines put a weakened or inactivated germ or virus into your body to trigger an immune response. However, mRNA vaccines are different. Instead, they teach your cells how to make a small, harmless piece of the virus to trigger an immune response inside our bodies. 

Advantages of Using mRNA Vaccines

Traditional vaccines typically require growing large amounts of infectious viruses and then inactivating them — a process that can take weeks or months. However, mRNA vaccines can be quickly designed, tested, and mass produced. mRNA vaccines are also safer because they do not contain live viruses.

How Do mRNA Vaccines Work?

The mRNA vaccines for COVID-19 are injected into the muscle of your upper arm. Once the mRNA is inside your body, your muscle cells will follow the genetic instructions that tells them how to make the spike protein (a small, harmless piece of the COVID-19 virus). The spike protein does not cause infection or cause people to become sick from COVID-19.

After the spike protein is made, your immune system will recognize that it doesn’t belong there. As a result, your immune system will begin making T-cells and antibodies that recognize the spike protein. 

This process teaches your body how to recognize and destroy the virus if you are ever infected with COVID-19 in the future. 

View Infographic

How Effective Are mRNA Vaccines Against COVID-19?

The Pfizer/BioNTech and Moderna vaccines are around very effective in preventing serious illness, hospitalization and death from COVID-19. 

What Are the Possible Side Effects of an mRNA Vaccine?

Participants in both the Pfizer/BioNTech and Moderna vaccine clinical trials have reported the following side effects:

  • mild pain, swelling, or redness at the injection site where you get the vaccine;
  • mild fever;
  • chills;
  • feeling tired;
  • headache; 
  • muscle and joint aches;
  • vomiting;
  • diarrhea (seen in Pfizer/BioNTech clinical trials);
  • nausea (seen in Moderna clinical trials); and
  • swollen lymph nodes in the same arm as the injection site (seen in Moderna clinical trials).

Some people who received the vaccine reported worse fevers and aches than others. Side effects were usually short-lived and able to be managed with fever-reducing medications, such as Tylenol. For people who received the Pfizer/BioNTech, Novavax, or Moderna vaccine, side effects were more common after the second dose than the first dose. 

No harmful side effects have been reported in clinical trials, however, the possibility of extremely rare harmful side effects could still exist. Clinical trials for these vaccines are ongoing. More information will become available once we know more.

Allergic Reactions to Vaccines

Severe allergic reactions or anaphylaxis to vaccines are extremely uncommon. If a severe allergic reaction does occur, it typically happens within a few minutes to one hour after receiving the vaccine. However, some people have experienced non-severe allergic reactions (i.e., hives, swelling, and wheezing) within four hours after getting vaccinated.

You should not get the COVID-19 vaccine if:

  • you have had a severe allergic reaction after a previous dose of the vaccine.
  • you have had a severe allergic reaction to any ingredient in the vaccine.
  • you are allergic to polyethylene-glycol (ingredient in both vaccines) or polysorbate (not an ingredient in either vaccine but is closely related to PEG). 

People with a history of immediate allergic reactions — even if it was not severe — to other vaccines or injectable therapies should consult with their doctor before getting the COVID-19 vaccine, according to CDC recommendations.

Myocarditis & mRNA Vaccines

There have been rare reports of people—particularly male adolescents and young adults—who received the mRNA vaccines (Pfizer/BioNTech & Moderna) and experienced symptoms of myocarditis or pericarditis (heart inflammation conditions) within several days of getting their shot. This rare adverse reaction occurred more often after the second dose of vaccination. Cases of myocarditis and pericarditis have also been reported in people who received the Novavax vaccine. But with proper treatment and care, most patients saw their symptoms improve quickly. However, it's important to keep in mind that the known risks of COVID-19 illness, such as long-term health problems, hospitalization, and even death, far outweigh the risks of having a rare adverse reaction to the vaccines.

Hear From Our Specialists