What types of COVID-19 vaccines are authorized or approved for use in the general public?

Many companies are working to develop a COVID-19 vaccine. For the most up-to-date information about each vaccine, visit CDC’s Different COVID-19 Vaccines.  The FDA has authorized the Pfizer and Moderna vaccines for emergency use. Scientists developed both the Pfizer and Moderna vaccines using a new vaccine technology called messenger RNA (mRNA).


How do mRNA vaccines work?

mRNA vaccines help our bodies build an immune response to the COVID-19 virus. The mRNA vaccine teaches our cells how to make a harmless protein that is unique to the virus that causes COVID-19. After our cells make copies of the protein, our immune system recognizes that the protein should not be in our body and builds antibodies to remember how to fight the virus if we are infected in the future.  An antibody is a protein produced by your immune system that can recognize a specific type of virus in your body. When you get infected, your body’s antibodies are able to recognize proteins on the surface of the COVID-19 virus to attack and stop it from replicating in your body. For a visual explanation of how mRNA vaccines work, watch Stat’s video “What are mRNA vaccines?” To learn more, visit CDC’s Understanding How COVID-19 Vaccines Work.


Can mRNA vaccines change my genes?

No, mRNA from the COVID-19 vaccine never enters the nucleus of the cell and does not affect or interact with your DNA. mRNA are naturally occurring genetic molecules that instruct our cells how to create proteins that build, maintain, and repair things in the body. Minutes after our cells make the proteins, the body destroys the mRNA using a special enzyme.

mRNA in vaccines are designed to withstand the enzyme a little bit longer (a few days at most) so that our cells can create enough of a harmless protein that is unique to the virus. After our cells make copies of the virus’ protein, our immune system is triggered and recognizes that the protein should not be in our body. Our body then builds antibodies so that it remembers how to fight the virus if we are infected in the future.


I heard several COVID-19 vaccines were approved for Emergency Use Authorization. What does that mean?

In certain emergency situations, the Food and Drug Administration (FDA) may issue an Emergency Use Authorization to provide more timely access to critical medicines when there are no other options available. An Emergency Use Authorization permits the FDA to allow medical products that have met certain criteria, to treat, diagnose, or prevent serious or life-threatening diseases to be used. Watch this short video from the FDA about Emergency Use Authorization.


How will we know if the vaccine is safe?

The FDA requires that vaccines undergo a rigorous scientific process, including three phases of clinical trials, before they authorize or approve the vaccine. The COVID-19 vaccines are subject to the same safety standards as other vaccine trials.  To date, the independent Data and Safety Monitoring Board overseeing Phase 3 trials of the Pfizer and Moderna vaccines has not identified or reported any serious safety concerns.

All phase 3 studies have Data Safety and Monitoring Boards. The boards are made up of independent scientists hired by the company to look at the safety data and check at regular intervals whether the company should cancel or continue with the study. Additionally, two independent advisory committees will review a vaccine’s safety data before it is made available to the public. These committees are the Vaccines and Related Biological Products Advisory Committee (VRBPAC), which advises the FDA, and the Advisory Committee on Immunization Practices (ACIP), which advises the CDC.  Learn more about the Vaccine safety and development process.


Do any of the vaccines contain harmful ingredients?

Today’s vaccines use only the ingredients they need to be as safe and effective as possible. Each ingredient in a vaccine serves a specific purpose: provide immunity (protection), keep the vaccine safe and long-lasting, and produce the vaccine. All vaccines contain antigens or elements that trigger the production of antigens. Antigens make vaccines work. They prompt the body to create the immune response needed to protect against infection.

Antigens come in several forms. The form used in a vaccine is chosen because studies show it is the best way to protect against a particular infection.  Other ingredients in vaccines may include preservatives, to keep germs out; adjuvants, to help boost the immune response to the vaccine; and additives, which help the vaccine stay effective while being stored. Each ingredient has a specific function and has been rigorously studied. These ingredients are safe for humans in the amounts used in vaccines.