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.
• Boost your body's protection, also called immunity, against catching the virus that causes COVID-19.
• Be a safer way to protect yourself compared to getting sick with the virus that causes COVID-19.

How much protection a COVID-19 vaccine gives depends on different factors. Factors that can affect how much you're protected with 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 how the virus that causes COVID-19 changes and what variants the vaccine protects against. Your level of protection also depends on timing, such as when you got the shot.

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

Yes. After you've had COVID-19, getting vaccinated can boost your body's protection against catching the virus that causes COVID-19 another time.

Getting COVID-19 or getting a COVID-19 vaccination gives you protection, also called immunity, from being infected again with the virus that causes COVID-19. But over time, that protection seems to fade. Getting COVID-19 again may cause serious illness or medical complications, especially for people with risk factors for severe COVID-19.

Researchers continue to study what happens when someone has COVID-19 a second time. Reinfections are generally milder than the first infection. But severe illness can still happen. Some people may see their risk of having to go to the hospital and having medical problems such as diabetes go up with each COVID-19 infection.

Research has found that people who have had COVID-19 and then have had all of the suggested COVID-19 vaccinations are less likely to be treated in the hospital due to COVID-19 than people who are not vaccinated or who haven't had all the suggested shots. This protection wears off in the months after getting the vaccine.

Also, because the virus that causes COVID-19 can change, also called mutate, a vaccination with the latest strain, or variant, that is spreading or expected to spread can help keep you from getting sick again.

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.

In general, people age 5 and older with typical immune systems can get any vaccine that is approved or authorized for their age. They usually don't need to get the same vaccine each time.

Some people should get all their vaccine doses from the same vaccine maker, including:

• Children ages 6 months to 4 years.
• People age 5 years and older with weakened immune systems.
• People age 12 and older who have had one shot of the Novavax vaccine should get the second Novavax shot in the two-dose series.

Talk to your healthcare professional if you have any questions about the vaccines for you or your child. Your healthcare team can help you if:

• The vaccine you or your child got earlier isn't available.
• You don't know which vaccine you or your child received.
• You or your child started a vaccine series but couldn't finish it due to side effects.

At the start of the COVID-19 pandemic, COVID-19 vaccines were needed right away. But the U.S. Food and Drug Administration's (FDA's) vaccine approval process can take years.

To provide vaccines sooner, the FDA gave emergency use authorization to COVID-19 vaccines based on less data than is typically required. But the data still has to show that the vaccines are safe and effective.

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.

Vaccines with FDA emergency use authorization or approval include:

• 2023-2024 Pfizer-BioNTech COVID-19 vaccine. This vaccine was first tested against the original strain of the COVID-19 virus. That strain began spreading at the end of 2019. In December 2020, the Pfizer-BioNTech COVID-19 vaccine two-dose series was found to be both safe and 91% to 95% 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. It is authorized 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.

• 2023-2024 Moderna COVID-19 vaccine. This vaccine also was first tested against the original strain of the virus that causes COVID-19. In December 2020, the Moderna COVID-19 vaccine was found to be both safe and about 93% effective in preventing infection among study volunteers, all age 18 or older.

  Based on the comparison between people who got COVID-19 in the placebo group, the Moderna COVID-19 vaccine was 98% effective at preventing serious COVID-19 illness. Vaccine effect was predicted for younger people based on that clinical trial data as well.

  The vaccine is approved under the name Spikevax for people age 12 and older. The vaccine is authorized for use 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.

• 2023-2024 Novavax COVID-19 vaccine, adjuvanted. This vaccine is available under an emergency use authorization for people age 12 and older. It requires two shots, given 3 to 8 weeks apart. Research done before the spread of the delta and omicron variants has shown that the vaccine is 90% effective at preventing mild, moderate and severe disease with COVID-19. For people age 65 and older, the vaccine is 79% effective.

Both the Pfizer-BioNTech and the Moderna COVID-19 vaccines use genetically engineered messenger RNA (mRNA). Coronaviruses have a spikelike structure on their surface called an S protein. COVID-19 mRNA vaccines give your cells instructions for how to make a harmless piece of an S protein.

After vaccination, your muscle cells begin making the S 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 the parts (proteins) of a virus that best stimulate your immune system. The Novavax COVID-19 vaccine contains harmless S proteins. It also has an ingredient called an adjuvant that helps with your immune system response.

Once your immune system recognizes the S proteins, this vaccine 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 currently being developed and used 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 or shed any vaccine parts.

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.

Many 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, including:

• Pain, redness or swelling where the shot was given.
• Fever.
• Fatigue.
• Headache.
• Muscle pain.
• Chills.
• Joint pain.
• Nausea and vomiting.
• Feeling unwell.
• Swollen lymph nodes.

Babies ages 6 months through 3 years old also might cry, feel sleepy or lose their appetite after vaccination. Children in this age group also may have the common side effects seen in adults. These include pain, redness or swelling where the shot was given, fever, or swollen lymph nodes.

A healthcare team watches you for 15 minutes after getting a COVID-19 vaccine to see if you have an allergic reaction.

If the redness or tenderness where the shot was given gets worse after 24 hours or you're worried about any side effects, contact your healthcare professional.

The vaccines that help protect against COVID-19 are safe and effective. The vaccines were tested in clinical trials. People continue to be watched for rare side effects, even after more than 650 million 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 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.

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

If you or your child develops myocarditis or pericarditis after getting a COVID-19 vaccine, talk to a healthcare professional before getting another dose of the vaccine.

Of the cases reported, the problem 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.

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.

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.

Your healthcare team may suggest you get added doses of a COVID-19 vaccine if you have a moderately or severely weakened immune system. 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. However, it's 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.

You might be having an immediate allergic reaction to a COVID-19 vaccine if you experience these symptoms within four hours of getting vaccinated:

• Hives.
• Swelling of the lips, eyes or tongue.
• Wheezing.

If you have any signs of an allergic reaction, get help right away. 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 you are allergic to the vaccine. You might not be able to get a second dose of the same vaccine. However, 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.

If you are pregnant or breastfeeding, the CDC recommends that you get a COVID-19 vaccine. Getting a COVID-19 vaccine can protect you from severe illness due to COVID-19. Vaccination also can help pregnant women build antibodies that might protect their babies.

COVID-19 vaccines don't cause infection with the virus that causes COVID-19, including in pregnant women or their babies. None of the COVID-19 vaccines contains the live virus that causes COVID-19.

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 are considered up to date with your vaccines if you have gotten all recommended COVID-19 vaccine shots when you become eligible.

After getting vaccinated, you can more safely return to doing activities that you might not have been able to do because of high numbers of people with COVID-19 in your area. However, if you're in an area with a high number of people with COVID-19 in the hospital, the CDC recommends wearing a well-fitted mask indoors in public, whether or not you're vaccinated.

If you have a weakened immune system or have a higher risk of serious illness, wear a mask that provides you with the most protection possible when you're in an area with a high number of people with COVID-19 in the hospital. Check with your healthcare professional to see if you should wear a mask at other times.

The CDC recommends that you wear a mask on planes, buses, trains and other public transportation traveling to, within or out of the U.S., as well as in places such as airports and train stations.

If you've gotten all recommended vaccine doses and you've had close contact with someone who has the COVID-19 virus, get tested at least five days after the contact happens.

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 develop symptoms, they tend to be less severe than those experienced by unvaccinated people.