Health Encyclopedia

COVID-19 vaccines

Definition

COVID-19 vaccines are used to prepare the body's immune system to protect against COVID-19.

Everyone ages 6 months and older should get an updated (2023-2024 formula) COVID-19 vaccine. This includes people who are pregnant and those planning to become pregnant. You should get an updated COVID-19 vaccine even if you have already had COVID-19.

Alternative Names

Vaccines for COVID-19; COVID-19 vaccinations; COVID-19 shots; Vaccinations for COVID-19; COVID-19 immunizations; COVID-19 prevention - vaccines; mRNA vaccine - COVID-19; COVID-19 vaccine booster shots; Booster shots for COVID-19

Information

HOW COVID-19 VACCINES WORK

COVID-19 vaccines protect people from getting COVID-19 and from getting more severe symptoms if they get COVID-19. These vaccines "teach" your body how to defend against the SARS-CoV-2 virus, which causes COVID-19.

COVID-19 vaccines have been shown to do a very good job of:

• Preventing infection with the SARS-CoV-2 virus, which causes COVID-19
• Protecting against serious illness, hospitalization, and death from COVID-19
• Reducing the risk of people spreading COVID-19

mRNA VACCINES

The mRNA vaccines approved in the United States work differently from many other vaccines.

• COVID-19 mRNA vaccines use messenger RNA (mRNA) to tell cells in the body how to briefly create a harmless piece of "spike" protein that is unique to the SARS-CoV-2 virus. Cells then get rid of the mRNA.
• This "spike" protein triggers an immune response inside your body, making antibodies that protect against COVID-19. Your immune system then learns to attack the SARS-CoV-2 virus if you are ever exposed to it.
• There are two mRNA COVID-19 vaccines currently approved for use in the United States, the Pfizer-BioNTech and the Moderna COVID-19 vaccines.

The COVID-19 mRNA vaccine is given as an injection (shot) in the arm. The original mRNA vaccines (monovalent and bivalent mRNA vaccines) are no longer available. The updated (2023-2024 formula) mRNA vaccines, also called homologous vaccines, are currently in use. These updated (2023-2024 formula) vaccines protect against the original COVID-19 virus and certain variants of the COVID-19 virus.

SUBUNIT VACCINE

The Novavax vaccine is a protein subunit vaccine. The vaccine includes harmless pieces of the "spike" protein that causes COVID-19. The vaccine triggers the body to develop antibodies to protect you from the virus. This updated (2023-2024 formula) vaccine protects against the original COVID-19 virus and certain variants of the COVID-19 virus. The original Novavax (monovalent) is no longer available. The updated (2023-2024 formula) is currently in use.

VACCINATION SCHEDULE

The vaccination schedule is based on your age, vaccination history, and whether you are moderately or severely immunocompromised.

• Everyone ages 5 years and older should get 1 dose of the updated (2023-2024 formula) Pfizer-BioNTech or Moderna COVID-19 vaccine, whether or not you received the original vaccines.
• People who are moderately or severely immunocompromised may get additional doses of the updated (2023-2024 formula) Pfizer-BioNTech, Moderna, or Novavax COVID-19 vaccines. Talk with your health care provider about additional updated doses.
• Children ages 6 months and older may need multiple doses of the updated (2023-2024 formula) Pfizer-BioNTech or Moderna COVID-19 vaccines. Talk with your provider about what is right for your child.

People ages 12 years and older also have the option to get the updated (2023-2024 formula) Novavax vaccine.

• People who have previously received any COVID-19 vaccine may get 1 dose of the updated (2023-2024 formula) Novavax vaccine at least 2 months after receiving the previous dose of a COVID-19 vaccine.
• People who have not previously had any COVID-19 vaccine may get the 2 doses of the updated (2023-2024 formula) Novavax vaccine, given 3 to 8 weeks apart.
• Some people ages 12 to 64 years may receive the second shot 8 weeks after the first shot (especially males ages 12 to 39 years). This may help reduce the very rare risk of certain rare side effects myocarditis and pericarditis (inflammation of the heart muscle or lining).

VACCINE MYTHS

COVID-19 vaccines:

• DO NOT contain any live virus, and they cannot give you COVID-19
• DO NOT affect or interfere with your genes (DNA)
• DO NOT affect or interfere with pregnancy, nor do they make you infertile

To get up-to-date accurate information about COVID-19 vaccines, go to the Centers for Disease Control and Prevention (CDC) website:

• Vaccines for COVID-19 - www.cdc.gov/coronavirus/2019-ncov/vaccines/index.html
• Bust Myths and Learn the Facts about COVID-19 Vaccines - www.cdc.gov/coronavirus/2019-ncov/vaccines/facts.html

VACCINE SIDE EFFECTS

While COVID-19 vaccines will not make you sick, they may cause certain side effects and flu-like symptoms. This is normal. These symptoms are a sign that your body is making antibodies against the virus.

Side effects can vary from person to person. Common side effects include:

• Pain, redness, or swelling on the arm where you got the shot
• Tiredness
• Headache
• Muscle pain
• Chills
• Fever
• Nausea
• Swollen lymph nodes

Some side effects from the shot may affect your ability to do daily activities, but they will go away in a few days.  Any side effects from the vaccine are far less dangerous than the potential for serious illness or death from COVID-19.

HOW TO GET THE VACCINE

There are several ways you can look for vaccination providers near you.

• Ask your child's health care provider if they offer COVID-19 vaccines.
• Contact your local health department.
• Go to the CDC website Vaccines.gov.
• Call 1-800-232-0233 to find vaccine locations near you.
• Check your local pharmacy's website to see if vaccination appointments are available.
• The CDCs Bridge Access Program provides free COVID-19 vaccines to adults who don't have health insurance and to adults who have insurance that does not cover all the cost of the vaccine.

Learn what to expect when you get your COVID-19 vaccine.

VACCINE SAFETY

The safety of vaccines is the top priority, and COVID-19 vaccines have passed rigorous safety standards before approval. Millions of people have received the vaccine, and no long-term side effects have been reported. They continue to be closely monitored to ensure they are safe and effective.

There have been reports of some people who have had an allergic reaction to the current vaccines. So it is important to follow certain precautions:

• If you have ever had a severe allergic reaction (anaphylaxis) to a particular type of COVID-19 vaccine, you should not get that vaccine. You may be able to get another type of COVID-19 vaccine.
• If you have a non-severe allergic reaction after getting the first shot of the COVID-19 vaccine, you may be able to get another dose in some cases. Your provider may refer you to an allergy and immunology provider for care.
• If you only had a skin rash on the arm you got the shot (COVID arm), you should still get additional shots.
  

If you have had an allergic reaction, even if not severe, to other vaccines or injectable therapies, you should ask your provider if you should get a COVID-19 vaccine. Your provider will help you decide if it is safe to get vaccinated.

Serious health events from COVID-19 vaccines, such as an allergic reaction, are rare. Adverse events after COVID-19 vaccination are very rare.

Rare cases of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the outer lining of the heart) have been reported in children and teens ages 5 years and older after getting the Pfizer-BioNTech and Moderna vaccine.

This reaction has tended to occur more often in male adolescents and young adults ages 12 to 39 years.

• It occurs more often after the second dose, most often within 7 days after vaccination. Studies show that this rare risk may be reduced by waiting 8 weeks between the first and second dose.
• With proper care and rest, most people who had the reaction got better quickly without any lasting effects.
• For people who had this rare reaction, it is important to talk with a cardiologist (heart doctor) about how and when to return to exercise and sports.

Symptoms of myocarditis and pericarditis include:

• Chest pain
• Shortness of breath
• Fast-beating heart, fluttering, or pounding heart

If your child or teenager has any of these symptoms, get medical help right away.

All these associations are so rare that they should not cause hesitation in receiving any of these vaccines.

CDC recommends that people may still get vaccinated if they have a history of:

• Severe allergic reactions NOT related to vaccines or injectable medicines -- such as food, pet, venom, environmental, or latex allergies
• Allergies to oral medicines or a family history of severe allergic reactions

References

Centers for Disease Control and Prevention website. Allergic reactions after COVID-19 vaccination. www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/allergic-reaction.html. Updated July 20, 2022. Accessed October 10, 2023.

Centers for Disease Control and Prevention website. Benefits of getting a COVID-19 vaccine. www.cdc.gov/coronavirus/2019-ncov/vaccines/vaccine-benefits.html. Updated September 22, 2023. Accessed October 10, 2023.

Centers for Disease Control and Prevention website. CDC's Bridge Access Program. www.cdc.gov/vaccines/programs/bridge/. Updated September 14, 2023. Accessed October 10, 2023.

Centers for Disease Control and Prevention website. COVID-19 vaccines for people who are moderately or severely immunocompromised. www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/immuno.html. Updated October 4, 2023. Accessed October 10, 2023.

Centers for Disease Control and Prevention website. COVID-19 vaccines for people who would like to have a baby. www.cdc.gov/coronavirus/2019-ncov/vaccines/planning-for-pregnancy.html. Updated September 22, 2023. Accessed October 10, 2023.

Centers for Disease Control and Prevention website. COVID-19: Selected adverse events reported after COVID-19 vaccination. www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/adverse-events.html. Updated September 12, 2023. Accessed October 10, 2023.

Centers for Disease Control and Prevention website. Interim clinical considerations for the use of COVID-19 vaccines in the United States. www.cdc.gov/vaccines/covid-19/clinical-considerations/interim-considerations-us.html. Updated October 6, 2023. Accessed October 10, 2023.

Centers for Disease Control and Prevention website. Myocarditis and pericarditis after mRNA COVID-19 vaccination. www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/myocarditis.html. Updated September 12, 2023. Accessed October 10, 2023.

Centers for Disease Control and Prevention website. Bust myths and learn the facts about COVID-19 vaccines. www.cdc.gov/coronavirus/2019-ncov/vaccines/facts.html. Updated September 27, 2023. Accessed October 10, 2023.

Centers for Disease Control and Prevention website. Stay up to date with COVID-19 vaccines. www.cdc.gov/coronavirus/2019-ncov/vaccines/stay-up-to-date.html. Updated October 4, 2023. Accessed October 10, 2023.

Centers for Disease Control and Prevention website. Use of COVID-19 vaccines in the United States. Interim clinical considerations. www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html. Updated October 6, 2023. Accessed October 10, 2023.

US Food & Drug Administration website. Novavax COVID-19 vaccine, adjuvanted. Novavax COVID-19 vaccine, adjuvanted (2023-2024 formula) authorized for individuals 12 years of age and older. www.fda.gov/vaccines-blood-biologics/coronavirus-covid-19-cber-regulated-biologics/novavax-covid-19-vaccine-adjuvanted. Updated October 4, 2023. Accessed October 10, 2023.

Review Date:2/22/2023
Reviewed By:Frank D. Brodkey, MD, FCCM, Associate Professor, Section of Pulmonary and Critical Care Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. Editorial update 10/10/2023.

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