COVID-19 Booster Shots: Answers to Frequently Asked Questions

COVID-19 Booster Shots: Answers to Frequently Asked Questions.

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Note: This blog was published on December 3, 2021. Please check the CDC website to stay up to date with the latest information. 


Change has been a constant theme throughout the COVID-19 pandemic. Regardless of what  professional athletes or celebrities might suggest, this is a good thing—science is all about learning and adapting to new information.

The progress we’ve made worldwide in preventing and treating COVID-19 is nothing short of incredible. But it will continue to be a bit of a bumpy ride as we make new science-based discoveries. 

The latest update many people are asking about is the COVID-19 booster shot—and how it’s different from additional vaccine doses recommended for immunocompromised patients. To provide more clarity, I’ll discuss questions we’re hearing the most from patients.

Keep in mind that we still have much to understand about the coronavirus. When searching for answers, stick to trusted health professionals and the Centers for Disease Control and Prevention (CDC) for the most up-to-date and accurate information.

It can be hard to keep up with #COVID19Vaccine information. Get answers to FAQs about the #COVIDBoosterShot from @MedStarWHC Section Director of Infectious Diseases Glenn W. Wortmann, MD:
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What is a COVID-19 booster shot?

Booster shots enhance your immune system’s ability to protect you from a COVID-19 infection. Boosters are approved from Moderna, Pfizer, and Johnson & Johnson, and include all the same ingredients as the manufacturer’s original vaccines.


New data is showing that the effectiveness of the COVID-19 vaccine slightly decreases over time. By getting a booster shot, adults who have received two full doses of the Moderna or Pfizer vaccine—or one dose of the Johnson & Johnson vaccine—can increase and extend their protection against the virus. If these people do not receive a booster shot, they are still considered fully vaccinated.


How is a booster shot different from an "additional dose" of the COVID-19 vaccine?

A booster shot extends protection against COVID-19 in people who developed high immunity to COVID after being fully vaccinated. An additional dose of the vaccine increases immunity in people who developed a low amount of immunity after being fully vaccinated.

Additional doses are not the same as booster shots. For example, the Moderna booster is only half of the dose administered for a primary series dose.

People who are immunocompromised are not likely to develop much immunity to COVID-19 after receiving two full doses of the Moderna or Pfizer vaccine or one dose of the Johnson & Johnson vaccine. This includes individuals who:

  • Are receiving immunosuppressive treatment for cancer or other medical conditions
  • Have received an organ or stem cell transplant 
  • Have an advanced or untreated HIV infection

The CDC recommends that immunocompromised individuals who received two doses of the Pfizer or Moderna vaccine get an additional full dose—from the same vaccine manufacturer—at least 28 days after the second dose. Sometimes a fourth dose is recommended, depending on the person’s health. 

Additional full doses of the Moderna and Pfizer vaccines have been shown to improve COVID-19 immunity in these patients. The CDC now recommends that anyone who received a single dose of Johnson & Johnson vaccine should get a second dose of a COVID vaccine 2 months after the first dose. It is preferred to use an mRNA vaccine (Moderna or Pfizer) for the best immune response. However, if this is unavailable, a repeat dose of J&J/Janssen can be given instead.

Talk with your doctor to see if you might benefit from an additional dose of the COVID-19 vaccine. It is not recommended for people who had a serious reaction to their initial vaccine series; have a fever over 100.4 degrees Fahrenheit; or have received a monoclonal antibody infusion (Regeneron or Lilly) in the last 90 days to treat COVID-19.

Who should get a booster shot—and when?

The U.S. Food and Drug Administration recently approved the Pfizer booster shot for all adults 18 and older.

We are following the CDC’s guidance to encourage all fully vaccinated adults to get a booster shot and strongly recommend it for people who are:

  • 18 or older and received the Johnson & Johnson vaccine two or more months ago
  • 65 or older and received the Pfizer or Moderna vaccine six or more months ago
  • 18 or older, received the Pfizer or Moderna vaccine six or more months ago, and have underlying medical conditions or live or work in high-risk environments (e.g., long-term care facility, health care setting, school, grocery or department store)

You can get a booster shot from any of the three vaccine manufacturers, no matter which type you received the first time. Some data has shown that mixing vaccines could provide better protection, but we still can’t say for sure. What we do know is that all three are highly effective.


Is the booster shot safe?

Just like the first COVID-19 vaccines, which contain the same ingredients, booster shots are not only safe but also protective against the Delta variant


Over 7 billion doses of the COVID-19 vaccine have been administered across the world, so we have excellent data showing that it is very safe. COVID-19 can become a severe infection that results in death or long-term symptoms, which is why we recommend vaccination so strongly. 


I understand people’s hesitancy to receive a new vaccine, especially when it doesn’t completely erase your chances of getting infected—even with a booster shot.


However, getting vaccinated significantly lowers your risk of experiencing severe COVID-19 symptoms if you do become infected. And it reduces the chances that you’ll spread an infection to people who have a high risk of developing severe COVID symptoms. Booster shots extend this protection to help you and the people you care about stay as healthy as possible.


Does the booster shot have side effects?

Reported side effects have been mild to moderate and similar to symptoms experienced after the first vaccines: fever, headache, fatigue, and pain at the injection site.


Mild side effects are triggered by the immune system’s reaction to learning how to fight the virus—and everyone’s body acts differently. Experiencing side effects does not mean the vaccine or booster shot gave you a virus. The vaccine also does not cause cancer or infertility.

Serious side effects from the COVID-19 vaccines are extremely rare. People who have an allergic reaction to their first dose should talk with their doctor about getting their next dose from a different manufacturer.

Will we need booster shots every year?

It’s too early to say what the future of COVID-19 vaccination looks like. It will likely depend on the spread of COVID over the next year or so—which should decrease as vaccination rates increase. 

The best way to reduce the number of COVID vaccinations recommended in the future is to become fully vaccinated now and receive a booster shot when you’re eligible—even if you’ve already had COVID-19. The natural immunity that develops after an infection does not last as long as the immunity from the vaccine.

MedStar Health patients can schedule a COVID-19 booster shot through their provider’s office. If you are not a current patient, review our list of clinics offering the vaccine.

Are you ready to receive your COVID-19 booster shot?

Request an appointment to extend your protection against COVID-19.

Call 202-877-DOCS (3627) or Request an Appointment

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