COVID-19 Vaccines: Covering the Basics

COVID-19 Vaccines: Covering the Basics

This article is for anyone who wants to learn more about COVID-19. The goal of this patient education activity is to help patients and their care partners talk to their doctors about COVID-19 vaccines and engage in shared decision-making.

You will learn about:

  • How COVID-19 can affect your body

  • How your immune system and vaccines work to protect you

  • Why vaccines are important

  • How and why COVID-19 vaccines are authorized for use in the United States

  • Possible side effects of the vaccines

  • Questions to ask your doctor

Medicines listed in this activity have either a US Food and Drug Administration (FDA) approval or have been given an Emergency Use Authorization (EUA) by the FDA to treat or prevent COVID-19.

The information on COVID-19 is continually changing. The content in this activity is accurate based on the information that was available at the time of its publication. This resource is provided for educational and informational purposes only. We do not provide medical advice, diagnosis, or treatment.

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How COVID-19 Affects Your Body

Once exposed to and infected by the virus that causes COVID-19, most people will have mild or no symptoms. But for others, COVID-19 can be severe and may even cause death. COVID-19 can damage many different organs and systems in your body. This can lead to symptoms and complications (additional problems) that can be long lasting.

Anyone can get COVID-19, but it is especially dangerous for elderly people and people who are pregnant, smoke, or have certain medical conditions.

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Your Immune System and COVID-19

Your immune system -- your body's natural defense system -- is made up of different organs, cells, and proteins that work to protect you when you're exposed to an outside invader, such as the virus that causes COVID-19.

When you're exposed, your immune system is triggered and activates certain cells and proteins, including antibodies. Antibodies are released into your bloodstream to attack the invader and fight off infection. It can take several days or weeks for antibodies to develop. But they stay in your body and can recognize and defend against the invader if you're exposed to it again.

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Antibodies (in purple) are made by certain cells in your body to attack a virus and fight off infection.

How Vaccines Work With Your Immune System

Vaccines have been used for hundreds of years to help protect us against many potentially deadly diseases, such as polio, tetanus, the flu, and hepatitis. Vaccines are given before an infection to try to prevent disease.

Once given, a vaccine triggers your body's immune system to make antibodies. This can give you protection (immunity) against future infection without having to get the disease first.

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Why Vaccines Are Important

Vaccines are important because they work to prevent disease, unlike other medicines that treat or cure a disease after you have it.

Because COVID-19 can cause long-lasting damage and be life-threatening, it's important to be protected against the illness and to prevent spreading it to others. A vaccine is a safer way to help build protection (immunity) than getting the disease. If you get COVID-19, you run the risk of severe illness and the damaging effects of COVID-19 on your body.

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How and Why COVID-19 Vaccines Are Authorized for Use in the US

The COVID-19 vaccines currently being used in the United States have an Emergency Use Authorization (EUA) from the FDA, the agency that makes sure medicines are safe and effective. A vaccine may get an EUA when the FDA has found that the known and potential benefits of using the vaccine outweigh the known and potential risks.

The vaccines are not yet approved by the FDA to prevent COVID-19, but the FDA is allowing their use because COVID-19 is a public health emergency and can be serious or life-threatening. The EUA process has been around for over 15 years and has been an important tool in past emergency situations.

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Do the Vaccines Work Against COVID-19?

The vaccines being used in the United States for COVID-19 were authorized for use because they have been shown to be safe and effective. Depending on which vaccine you get, you will get 1 shot, or 2 shots a few weeks apart.

It usually takes a few weeks for your body to build up immunity after your final shot. So it's still possible to get COVID-19 just before getting the vaccine or just after if your body hasn't had enough time to build up protection. When you get your shot, be sure to ask when you will be fully protected.

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Possible Side Effects

All vaccines can have side effects. Possible side effects that may happen with COVID-19 vaccines can include:

  • Pain, redness, or swelling where the shot was given

  • Headache

  • Fatigue (tiredness)

  • Fever

  • Muscle aches

  • Nausea

There is a very small chance that some people may develop:

  • A severe allergic reaction that usually happens within a few minutes to an hour after getting the shot

  • Blood clots in vessels in the brain, abdomen (belly), and legs, depending on which vaccine you get

Not all side effects are listed here. Ask your doctor, pharmacist, or the person giving you your vaccine for a full list and when you should contact your doctor or seek medical attention because of side effects.

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Getting the COVID-19 Vaccine

The vaccine can help protect you and those around you from COVID-19.

You can't get COVID-19 from the vaccines because they don't contain the live virus that causes COVID-19. And even though the vaccines were developed as quickly as possible because of the pandemic, the FDA has specific procedures that always stay in place to check the safety of any vaccine before it is authorized or approved for use.

Check with your doctor, pharmacist, or state's department of health website about where to get a vaccine in your area.

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Collin talks about his decision and experience with getting the COVID-19 vaccine.

Questions to Ask Your Doctor

Questions you can ask your doctor or pharmacist about the COVID-19 vaccine can include:

  • Which vaccines are available and how many shots will I need?

  • What are the possible side effects?

  • Can I still get the vaccine if I've had COVID-19?

  • When and where can I get a vaccine?

  • What can I expect when I get the vaccine and when will I be fully protected?

  • What should I do after getting the vaccine?

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You have successfully completed the program COVID-19 Vaccines: Covering the Basics.

View Additional Materials on this topic that you may find useful:

Patient Handout

Vaccines for COVID-19

Your COVID-19 Vaccination

Different COVID-19 Vaccines

Key Things to Know About COVID-19 Vaccines

COVID-19 Vaccine FAQs

Benefits of Getting a COVID-19 Vaccine

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Authors and Disclosures

Clinician Reviewer

Susan L. Smith, MN, PhD

Senior Director, Learning & Development, Medscape, LLC.

Disclosure: Susan L. Smith, MN, PhD, has disclosed no relevant financial relationships.


Anita A. Galdieri, PharmD, RPh

Associate Medical Education Director, Medscape, LLC.

Disclosure: Anita A. Galdieri, PharmD, RPh, has disclosed no relevant financial relationships.


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