COVID-19 vaccines: Get the facts

As the coronavirus disease 2019 (COVID-19) continues to cause illness, you might have questions about COVID-19 vaccines. Find out about the different types of COVID-19 vaccines, how they work, the possible side effects, and the benefits for you and your family.

Staying up to date with a COVID-19 vaccine can:

• Help prevent serious illness and death due to COVID-19 for both children and adults.
• Help prevent you from needing to go to the hospital due to COVID-19.
• Be a less risky way to protect yourself compared to getting sick with the virus that causes COVID-19.
• Lower long-term risk for cardiovascular complications after COVID-19.

Factors that can affect how well you're protected after a vaccine can include your age, if you've had COVID-19 before or if you have medical conditions such as cancer.

How well a COVID-19 vaccine protects you also depends on timing, such as when you got the shot. And your level of protection depends on how the virus that causes COVID-19 changes and what variants the vaccine protects against.

Talk to your healthcare team about how you can stay up to date with COVID-19 vaccines.

Yes. Catching the virus that causes COVID-19 or getting a COVID-19 vaccination gives you protection, also called immunity, from the virus. But over time, that protection seems to fade. The COVID-19 vaccine can boost your body's protection.

Also, the virus that causes COVID-19 can change, also called mutate. Vaccination with the most up-to-date variant that is spreading or expected to spread helps keep you from getting sick again.

Researchers continue to study what happens when someone has COVID-19 a second time. Later infections are generally milder than the first infection. But severe illness can still happen. Serious illness is more likely among people older than age 65, people with more than four medical conditions and people with weakened immune systems.

The COVID-19 vaccines available in the United States are:

• 2023-2024 Pfizer-BioNTech COVID-19 vaccine, available for people age 6 months and older.
• 2023-2024 Moderna COVID-19 vaccine, available for people age 6 months and older.
• 2023-2024 Novavax COVID-19 vaccine, available for people age 12 years and older.

These vaccines have U.S. Food and Drug Administration (FDA) emergency use authorization or approval.

In December 2020, the Pfizer-BioNTech COVID-19 vaccine two-dose series was found to be both safe and effective in preventing COVID-19 infection in people age 18 and older. This data helped predict how well the vaccines would work for younger people. The effectiveness varied by age.

The Pfizer-BioNTech vaccine is approved under the name Comirnaty for people age 12 and older. The FDA authorized the vaccine for people age 6 months to 11 years. The number of shots in this vaccination series varies based on a person's age and COVID-19 vaccination history.

In December 2020, the Moderna COVID-19 vaccine was found to be both safe and effective in preventing infection and serious illness among people age 18 or older. The vaccine's ability to protect younger people was predicted based on that clinical trial data.

The FDA approved the vaccine under the name Spikevax for people age 12 and older. The FDA authorized use of the vaccine in people age 6 months to 11 years. The number of shots needed varies based on a person's age and COVID-19 vaccination history.

In July 2022, this vaccine was found to be safe and effective and became available under an emergency use authorization for people age 18 and older.

In August 2022, the FDA authorized the vaccine for people age 12 and older. The number of shots in this vaccination series varies based on a person's age and COVID-19 vaccination history.

In August 2022, the FDA authorized an update to the Moderna and the Pfizer-BioNTech COVID-19 vaccines. Both included the original and omicron variants of the virus that causes COVID-19. In June 2023, the FDA directed vaccine makers to update COVID-19 vaccines. The vaccines were changed to target a strain of the virus that causes COVID-19 called XBB.1.5. In September and October 2023, the FDA authorized the use of the updated 2023-2024 COVID-19 vaccines made by Novavax, Moderna and Pfizer-BioNTech.

COVID-19 vaccines help the body get ready to clear out infection with the virus that causes COVID-19.

Both the Pfizer-BioNTech and the Moderna COVID-19 vaccines use genetically engineered messenger RNA (mRNA). The mRNA in the vaccine tells your cells how to make a harmless piece of virus that causes COVID-19.

After you get an mRNA COVID-19 vaccine, your muscle cells begin making the protein pieces and displaying them on cell surfaces. The immune system recognizes the protein and begins building an immune response and making antibodies. After delivering instructions, the mRNA is immediately broken down. It never enters the nucleus of your cells, where your DNA is kept.

The Novavax COVID-19 adjuvanted vaccine is a protein subunit vaccine. These vaccines include only protein pieces of a virus that cause your immune system to react the most. The Novavax COVID-19 vaccine also has an ingredient called an adjuvant that helps raise your immune system response.

With a protein subunit vaccine, the body reacts to the proteins and creates antibodies and defensive white blood cells. If you later become infected with the COVID-19 virus, the antibodies will fight the virus. Protein subunit COVID-19 vaccines don't use any live virus and can't cause you to become infected with the COVID-19 virus. The protein pieces also don't enter the nucleus of your cells, where your DNA is kept.

No. The COVID-19 vaccines available in the U.S. don't use the live virus that causes COVID-19. Because of this, the COVID-19 vaccines can't cause you to become sick with COVID-19.

It can take a few weeks for your body to build immunity after getting a COVID-19 vaccination. As a result, it's possible that you could become infected with the virus that causes COVID-19 just before or after being vaccinated.

Some people have no side effects from the COVID-19 vaccine. For those who get them, most side effects go away in a few days.

A COVID-19 vaccine can cause mild side effects after the first or second dose. Pain and swelling where people got the shot is a common side effect. That area also may look reddish on white skin. Other side effects include:

• Fever or chills.
• Headache.
• Muscle pain or joint pain.
• Tiredness, called fatigue.
• Upset stomach or vomiting.
• Swollen lymph nodes.

For younger children up to age 4, symptoms may include crying or fussiness, sleepiness, loss of appetite, or, less often, a fever.

In rare cases, getting a COVID-19 vaccine can cause an allergic reaction. Symptoms of a life-threatening allergic reaction can include:

• Breathing problems.
• Fast heartbeat, dizziness or weakness.
• Swelling in the throat.
• Hives.

If you or a person you're caring for has any life-threatening symptoms, get emergency care.

Less serious allergic reactions include a general rash other than where you got the vaccine, or swelling of the lips, face or skin other than where you got the shot. Contact your healthcare professional if you have any of these symptoms.

You may be asked to stay where you got the vaccine for about 15 minutes after the shot. This allows the healthcare team to help you if you have an allergic reaction. The healthcare team may ask you to wait for longer if you had an allergic reaction from a previous shot that wasn't serious.

Contact a healthcare professional if the area where you got the shot gets worse after 24 hours. And if you're worried about any side effects, contact your healthcare team.

The vaccines that help protect against COVID-19 are safe and effective. Clinical trials tested the vaccines to make sure of those facts. Healthcare professionals, researchers and health agencies continue to watch for rare side effects, even after hundreds of millions of doses have been given in the United States.

Side effects that don't go away after a few days are thought of as long term. Vaccines rarely cause any long-term side effects.

If you're concerned about side effects, safety data on COVID-19 vaccines is reported to a national program called the Vaccine Adverse Event Reporting System in the U.S. This data is available to the public. The U.S. Centers for Disease Control and Protection (CDC) also has created v-safe, a smartphone-based tool that allows users to report COVID-19 vaccine side effects.

If you have other questions or concerns about your symptoms, talk to your healthcare professional.

In some people, COVID-19 vaccines can lead to heart complications called myocarditis and pericarditis. Myocarditis is the swelling, also called inflammation, of the heart muscle. Pericarditis is the swelling, also called inflammation, of the lining outside the heart.

Symptoms to watch for include:

• Chest pain.
• Shortness of breath.
• Feelings of having a fast-beating, fluttering or pounding heart.

If you or your child has any of these symptoms within a week of getting a COVID-19 vaccine, seek medical care.

The risk of myocarditis or pericarditis after a COVID-19 vaccine is rare. These conditions have been reported after COVID-19 vaccination with any of the vaccines offered in the United States. Most cases have been reported in males ages 12 to 39.

These conditions happened more often after the second dose of the COVID-19 vaccine and typically within one week of COVID-19 vaccination. Most of the people who got care felt better after receiving medicine and resting.

These complications are rare and also may happen after getting sick with the virus that causes COVID-19. In general, research on the effects of the most used COVID-19 vaccines in the United States suggests the vaccines lower the risk of complications such as blood clots or other types of damage to the heart.

If you have concerns, your healthcare professional can help you review the risks and benefits based on your health condition.

In the U.S., COVID-19 vaccines may be offered at no cost through insurance coverage. For people whose vaccines aren't covered or for those who don't have health insurance, options are available. Anyone younger than 18 years old can get no-cost vaccines through the Vaccines for Children program. Adults can get no-cost COVID-19 vaccines through the temporary Bridges to Access program, which is scheduled to end in December 2024.

Yes, COVID-19 vaccines are safe for people who have existing health conditions, including conditions that have a higher risk of getting serious illness with COVID-19.

The COVID-19 vaccine can lower the risk of death or serious illness caused by COVID-19. Your healthcare team may suggest that you get added doses of a COVID-19 vaccine if you have a moderately or severely weakened immune system.

Cancer treatments and other therapies that affect some immune cells also may affect your COVID-19 vaccine. Talk to your healthcare professional about timing additional shots and getting vaccinated after immunosuppressive treatment.

Talk to your healthcare team if you have any questions about when to get a COVID-19 vaccine.

Don't take medicine before getting a COVID-19 vaccine to prevent possible discomfort. It's not clear how these medicines might impact the effectiveness of the vaccines. It is OK to take this kind of medicine after getting a COVID-19 vaccine, as long as you have no other medical reason that would prevent you from taking it.

Symptoms of a life-threatening allergic reaction can include:

• Breathing problems.
• Fast heartbeat, dizziness or weakness.
• Swelling in the throat.
• Hives.

If you or a person you're caring for has any life-threatening symptoms, get emergency care right away.

Less serious allergic reactions include a general rash other than where you got the vaccine, or swelling of the lips, face or skin other than where the shot was given. Contact your healthcare professional if you have any of these symptoms.

Tell your healthcare professional about your reaction, even if it went away on its own or you didn't get emergency care. This reaction might mean that you are allergic to the vaccine. You might not be able to get a second dose of the same vaccine. But you might be able to get a different vaccine for your second dose.

If you have a history of severe allergic reactions not related to vaccines or injectable medicines, you may still get a COVID-19 vaccine. You're typically monitored for 30 minutes after getting the vaccine.

If you've had an immediate allergic reaction to other vaccines or injectable medicines, ask your healthcare professional about getting a COVID-19 vaccine. If you've ever had an immediate or severe allergic reaction to any ingredient in a COVID-19 vaccine, the CDC recommends not getting that specific vaccine.

If you have an immediate or severe allergic reaction after getting the first dose of a COVID-19 vaccine, don't get the second dose. But you might be able to get a different vaccine for your second dose.

The CDC recommends getting a COVID-19 vaccine if:

• You are planning to or trying to get pregnant.
• You are pregnant now.
• You are breastfeeding.

Staying up to date on your COVID-19 vaccine helps prevent severe COVID-19 illness. It also may help a newborn avoid getting COVID-19 if you are vaccinated during pregnancy.

People at higher risk of serious illness can talk to a healthcare professional about additional COVID-19 vaccines or other precautions. It also can help to ask about what to do if you get sick so that you can quickly start treatment.

While rare, some children can become seriously ill with COVID-19 after getting the virus that causes COVID-19.

A COVID-19 vaccine might prevent your child from getting the virus that causes COVID-19. It also may prevent your child from becoming seriously ill or having to stay in the hospital due to the COVID-19 virus.

You can more safely return to activities that you might have avoided before your vaccine was up to date. You also may be able to spend time in closer contact with people who are at high risk for serious COVID-19 illness.

But vaccines are not 100% effective. So taking other action to lower your risk of getting COVID-19 still helps protect you and others from the virus. These steps are even more important when you're in an area with a high number of people with COVID-19 in the hospital. Protection also is important as time passes since your last vaccination.

If you are at higher risk for serious COVID-19 illness, basic actions to prevent COVID-19 are even more important. Some examples are:

• Avoid close contact with anyone who is sick or has symptoms, if possible.
• Use fans, open windows or doors, and use filters to move the air and keep any germs from lingering.
• Wash your hands well and often with soap and water for at least 20 seconds. Or use an alcohol-based hand sanitizer with at least 60% alcohol.
• Cough or sneeze into a tissue or your elbow. Then wash your hands.
• Clean and disinfect high-touch surfaces. For example, clean doorknobs, light switches, electronics and counters regularly.
• Spread out in crowded public areas, especially in places with poor airflow. This is important if you have a higher risk of serious illness.
• The CDC recommends that people wear a mask in indoor public spaces if COVID-19 is spreading. This means that if you're in an area with a high number of people with COVID-19 in the hospital a mask can help protect you. The CDC suggests wearing the most protective mask possible that you'll wear regularly, that fits well and is comfortable.

COVID-19 vaccination will protect most people from getting sick with COVID-19. But some people who are up to date with their vaccines may still get COVID-19. These are called vaccine breakthrough infections.

People with vaccine breakthrough infections can spread COVID-19 to others. However, people who are up to date with their vaccines but who have a breakthrough infection are less likely to have serious illness with COVID-19 than those who are not vaccinated. Even when people who are vaccinated get symptoms, they tend to be less severe than those felt by unvaccinated people.

Researchers continue to study what happens when someone has COVID-19 a second time. Reinfections and breakthrough infections are generally milder than the first infection. But severe illness can still happen. Serious illness is more likely among people older than age 65, people with more than four medical conditions and people with weakened immune systems.