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COVID-19 vaccines

COVID-19 vaccines are used to prepare the body's immune system to protect against COVID-19. These vaccines are a vital tool to help stop the COVID-19 pandemic.

Everyone age 5 and older should get a free COVID-19 vaccination. This includes people who are pregnant and those planning to become pregnant. You should get a COVID-19 vaccine even if you have already had COVID-19.

Information

HOW COVID-19 VACCINES WORK

COVID-19 vaccines protect people from getting 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
COVID-19 vaccine

The first COVID-19 vaccines approved in the United States are called mRNA vaccines. They 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 in 2 doses.

  • If you get the Pfizer COVID-19 vaccine, you should get your second shot about 21 days (3 weeks) after the first shot.
  • If you get the Moderna COVID-19 vaccine, you should get your second shot about 28 days (4 weeks) after the first shot.

People who have a weak immune system (immunocompromised) should get an additional dose at least 28 days after their second shot of either the Pfizer or Moderna mRNA vaccine. This includes people receiving certain types of cancer treatment and people taking medicines that suppress the immune system. Ask your doctor if you are not sure. Getting a third dose will improve the response to the vaccine in people with weak immune systems.

Children ages 5 to 17 can get the Pfizer-BioNTech mRNA vaccine. This is the only vaccine available to this age group at this time. The Pfizer vaccine given to children and teens has the same active ingredients as the vaccine given to adults.

  • Children age 12 and older get the same vaccine dosage of the Pfizer vaccine as adults.
  • Children age 5 through 11 get a smaller dose of the Pfizer vaccine. It is about one-third of an adult dose. A smaller needle is also used.
  • For all children, the shot is given as an injection (shot) in the arm in 2 doses.
  • The second shot is given about 21 days (3 weeks) after the first shot.

VIRAL VECTOR VACCINES

These vaccines are also effective at protecting against COVID-19.

  • They use a virus (a vector) that has been changed so that it can't harm the body. This virus carries instructions that tell the cells of the body to create the "spike" protein unique to the SARS-CoV-2 virus.
  • This triggers your immune system to attack the SARS-CoV-2 virus if you are ever exposed to it.
  • The Johnson and Johnson's Janssen (J&J/Janssen) COVID-19 vaccine is a viral vector vaccine. It has been approved for use in the United States. You only need one shot for this vaccine to protect you against COVID-19.

It takes time for your immune system to start protecting you after receiving the vaccine. You are considered fully vaccinated:

  • 2 weeks after your second shot of the Pfizer or Moderna vaccine
  • 2 weeks after your one shot of the J&J/Janssen vaccine

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:

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. Common side effects include:

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

Side effects from the shot may affect your ability to do daily activities, but they will go away in a few days. Even if you have side effects, you should get the second shot. 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.

  • Go to the CDC VaccineFinder.
  • Text your zip code to 438829 or call 1-800-232-0233 to find vaccine locations near you.
  • Check your local pharmacy's website to see if vaccination appointments are available. Find out which pharmacies are participating in the Federal Retail Pharmacy Program.

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 to any ingredient in a COVID-19 vaccine, you should not get one of the current COVID-19 vaccines.
  • If you have ever had an immediate allergic reaction (hives, swelling, wheezing) to any ingredient in the COVID-19 vaccine, you should not get one of the current COVID-19 vaccines.
  • If you have a severe or non-severe allergic reaction after getting the first shot of the COVID-19 vaccine, you should not get the second shot.

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

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

To learn more about COVID-19 vaccine safety, go to the CDC web site:

VACCINE BOOSTER SHOTS

Over time, COVID-19 vaccines appear to become less protective against the virus. Getting a booster dose helps provide additional protection against COVID-19. As a result, booster shots are now recommended for all adults age 18 and older.

If you received the Pfizer or Moderna mRNA vaccine, you can get a booster dose 6 months after receiving your second dose of the initial vaccine.

If you received the J&J/Janssen vaccine, you can get a booster dose 2 months after receiving your initial vaccine.

You have the option to choose any of the available vaccines (Pfizer, Moderna, or Janssen) for your booster dose, regardless of which vaccine you first received.  

The CDC has further information about COVID vaccine booster shots

WHAT YOU CAN DO ONCE YOU ARE FULLY VACCINATED

The CDC has recommendations for what it is safe to do once you are fully vaccinated.

We are still learning how well vaccines help prevent COVID-19 from spreading and how long the protection they provide lasts. Until more is known, using vaccines, masks, and taking other steps to help protect others is the best way to stay safe and healthy.

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; COVID-19 vaccine booster shots; Booster shots for COVID-19

References

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 November 18, 2021. Accessed November 22, 2021.

Centers for Disease Control and Prevention website. CDC Expands eligibility for COVID-19 booster shots.  www.cdc.gov/media/releases/2021/p1021-covid-booster.html. Updated October 21, 2021. Accessed October 22, 2021.

Centers for Disease Control and Prevention website. COVID-19 vaccines for children and teens. www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/children-teens.html. Updated November 19, 2021. Accessed November 22, 2021.

Centers for Disease Control and Prevention website. COVID-19 vaccines for moderately to severely immunocompromised people. www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/immuno.html. Updated October 18, 2021. Accessed October 22, 2021. 

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 November 11, 2021. Accessed November 22, 2021. 

Centers for Disease Control and Prevention website. Different COVID-19 vaccines. www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines.html. Updated November 9, 2021. Accessed November 22, 2021.

Centers for Disease Control and Prevention website. Interim clinical considerations for use of COVID-19 vaccines currently authorized in the United States. www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html#overview-covid19-vax-recommendations. Updated November 19, 2021. Accessed November 22, 2021.

Centers for Disease Control and Prevention website. Myths and facts about COVID-19 vaccines. www.cdc.gov/coronavirus/2019-ncov/vaccines/facts.html. Updated November 12, 2021. Accessed November 22, 2021.

Centers for Disease Control and Prevention website. Understanding viral vector COVID-19 vaccines. www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/viralvector.html. Updated October 18, 2021. Accessed October 22, 2021.

Centers for Disease Control and Prevention website. What to do if you have an allergic reaction after getting a COVID-19 vaccine. www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/allergic-reaction.html. Updated October 7, 2021. Accessed October 22, 2021.

Centers for Disease Control and Prevention website. When you've been fully vaccinated: How to protect yourself and others. www.cdc.gov/coronavirus/2019-ncov/vaccines/fully-vaccinated.html. Updated October 15, 2021. Accessed October 22, 2021.

Centers for Disease Control and Prevention website. Who is eligible for a COVID-19 booster shot? www.cdc.gov/coronavirus/2019-ncov/vaccines/booster-shot.html. Updated November 19, 2021. Accessed November 22, 2021.

Review Date 10/22/2021

Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. Editorial update 11/22/2021.