mRNA COVID-19 vaccine fast facts

• Two mRNA vaccines are available: Pfizer-BioNTech and Moderna.

• Pfizer-BioNTech and Moderna vaccines are available for people as young as 6 months old. The CDC recommends the most current COVID-19 vaccines for all people 6 months and older.

• The vaccine is given as a shot in a muscle.

• The mRNA vaccine does not use live, dead, or weak COVID virus.

• The vaccine will not give you COVID-19.

• Side effects of the vaccine mean your immune system is working, not that you have the virus.

• Talk with your health care provider to find out if you are up to date on your COVID-19 doses, or visit the CDC website.

• Vaccine recommendations are based on age. And, in some cases, the time since the previous dose is considered. The first vaccine received and a person's immunocompromised status may also be considered.

What does the COVID-19 vaccine do?

The COVID-19 vaccine has been shown to work well to prevent symptomatic and severe COVID-19 illness. Getting a COVID-19 vaccine can help protect you and your family from getting ill from the virus. If you get the virus after you get the vaccine, it may help your symptoms be milder. It also lowers your chance of needing a hospital stay because of COVID-19. The COVID-19 vaccine may also help protect people around you from getting the infection.

COVID-19 vaccines may also lead to more widespread changes. The more people who get the COVID-19 vaccine, the less likely the virus will be able to spread in the community. This is called herd immunity or community immunity.

Should you get a COVID-19 vaccine?

Everyone 6 months and older is advised to get vaccinated against COVID-19. This includes those who are pregnant or breastfeeding. The most important thing to do is talk with your health care provider about your risks and which vaccine is best for you and your family.

It is especially important to get the most current COVID-19 vaccine if you are age 65 or older, are at high risk for severe COVID-19, or have never received a COVID-19 vaccine.

Tell your provider if you have ever had a severe allergic reaction to food or medicine. Talk with them about your risks if you carry an epinephrine autoinjector. This may affect your provider’s advice to you about the vaccine.

Vaccine protection decreases over time, so it's important to get the most current COVID-19 vaccine.

How does an mRNA COVID-19 vaccine work?

The COVID-19 mRNA vaccines are different from traditional vaccines. They’re not made with live, dead, or weak virus. Instead, they're made with messenger ribonucleic acid (mRNA). This is a type of molecule that gives instructions for how to make different kinds of proteins. mRNA molecules are a natural part of our cells and how our bodies work.

The mRNA in the vaccines tells your cells how to make a harmless piece of a protein called a spike protein. This protein is found on the outside of the SARS-CoV-2 virus that causes COVID-19. Your immune system sees this spike protein as a threat, and creates antibodies and other defenses against it.

This will help your body's immune system recognize and fight the real virus if it ever shows up. It’s kind of like recognizing someone by the hat they wear. Your body is then prepared to spot COVID-19 and fight it off before it grows in your body’s cells.

How were the COVID-19 vaccines approved for safety?

The COVID-19 mRNA vaccines have passed many tests in labs and in tens of thousands of people and meet strict standards from the FDA.

The vaccines were tested first in animals. They were then tested in a series of clinical trials that included tens of thousands of people. All of the data from these tests were collected and submitted to the FDA and other scientific groups. These committees of scientists and public health experts carefully look at the data to see if a vaccine is safe and effective. If the vaccine meets the FDA's strict standards of safety and quality, the agency tells the vaccine company they can make the vaccine for emergency use.

How much does the vaccine cost?

Most people can get COVID-19 vaccines at no cost through private health insurance or government programs like Medicare and Medicaid. But the site where you get your vaccine may bill your health insurer for giving you the vaccine. Talk with your health insurer, local pharmacy, employer, or health care provider to find out more about a possible cost.

If you do not have health insurance or your insurance does not cover all COVID-19 vaccine costs, you may be able to find a free COVID-19 vaccine. Contact your local health department or find a local Health Resources and Services Administration (HRSA)-supported health center .

Getting the mRNA COVID-19 vaccine

The vaccine is given as a shot in a muscle. You may need to have more than one dose, spaced several weeks apart.

Follow instructions from the health care staff. Tell the staff if you have ever had a severe allergic reaction to food or medicine or carry an epinephrine autoinjector. Tell them if you feel any reaction after you have the shot. You may be asked to stay for some time after getting the vaccine so you can be watched.

Side effects: What to expect

The vaccine will have side effects for some people. A vaccine activates a person’s immune system. It causes the immune system to create antibodies to fight off a specific virus or bacteria. When your immune system goes into action, you may feel your immune system kick into gear as though it’s fighting an illness. This does not mean you are infected with an illness. It means that your immune system is working.

People getting the mRNA COVID-19 vaccines often have soreness where the shot was given, tiredness, headaches, muscle and joint aches, chills, and fever for 1 or 2 days. Fewer people have redness and swelling at the injection site. These are all signs that your immune system is working on its defense. You can get these kinds of effects after many kinds of vaccines. But these symptoms should last a short time. In comparison, COVID-19 symptoms can be severe and last much longer, and cause complications, long-term illness, and death. The FDA approval process makes sure that the discomfort and risks of a vaccine outweigh the risks and complications of the illness it helps prevent.

Allergic reactions

In general, the COVID-19 vaccines are very safe. They have been tested on thousands of people and given to more than a billion people. Non-severe allergic reactions have happened in a few people up to 4 hours after getting the vaccine. The vaccine clinic may ask you to stay on-site for a period of time after you get the vaccine. This is to make sure you don't have an immediate reaction.

Talk with your health care provider before you get a COVID-19 vaccine. Tell them if you have ever had an immediate reaction to any vaccine, even if the reaction was not severe. Your provider will help you weigh the risks and benefits of the COVID-19 vaccine for you.

If you have an allergy to any ingredient in the mRNA COVID-19 vaccine or had a severe allergic reaction to a previous COVID-19 vaccine dose, talk with your provider. They may advise you get a different type of COVID-19 vaccine.

The CDC has a smartphone app called V-Safe to help you report side effects. The app will also send you reminders if you need a second vaccine dose.

Severe symptoms

Severe allergic reactions to vaccines are rare but can happen. If you get a COVID-19 vaccine and think you may be having a severe allergic reaction after leaving the vaccine clinic, call 911.

Severe symptoms include:

• Trouble breathing.

• Wheezing.

• Trouble swallowing or feeling like your throat is closing.

• Cool, moist, pale, or blue-tinted skin.

• Hoarse voice or trouble speaking.

• Chest pain.

• Fainting.

• Swelling in the eyes, mouth, face, or tongue.

• Seizure.

• Feeling very drowsy or having trouble waking up.

• Fast heart rate.

• Nausea, vomiting, diarrhea, stomach cramps, or abdominal (belly) pain.

After you get the COVID-19 vaccine

When you get the COVID-19 vaccine:

• It’s still possible to get COVID-19. Like most vaccines, the COVID-19 vaccines are not 100% effective at preventing the disease. You should still take care to prevent contact with sick people and follow local advice about staying safe.

• Follow your local, state, and national instructions for protecting yourself and others from COVID-19.

Date last modified: 3/19/2025