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What Is the Difference Between the Third Dose and Booster COVID-19 Vaccine?

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Ochsner Health is now administering the third dose and booster COVID-19 vaccine for those who meet certain criteria laid out by the FDA, CDC and the Louisiana Department of Health.

What is the is the difference between a booster shot and a third dose?

We understand that the terms “third dose” and “booster shot” can cause some confusion. While they may seem similar, these terms are not interchangeable.

The term “third dose” is used for vaccinations for immunocompromised patients. A third dose of the vaccine is designed to be identical to the first two doses of the COVID-19 vaccine to protect people with a weakened immune system who did not have a strong enough response to the first two doses of the mRNA vaccine. Both the Pfizer and the Moderna mRNA COVID-19 vaccines are available as third doses.

The “booster shot” is designed to help people maintain immunity for a longer period once the initial doses’ protection has begun to decrease. Booster doses for all three COVID-19 vaccines, Pfizer, Moderna and Johnson & Johnson, are now available to the public and are being administered at Ochsner Health vaccination locations.

What does the third dose do?

The third dose of both the Pfizer and Moderna COVID-19 vaccines can help immunocompromised patients increase their antibody levels against COVID-19. Immunocompromised patients are some of the most susceptible to the serious effects of COVID-19 and may not respond to vaccines as well. It critical to provide them with all the information and resources they need to stay safe and healthy.

What does a booster shot do?

The booster shot is intended to “boost” the initial two doses’ long-term protection. A booster shot will help strengthen protection against severe disease for those at high risk for exposure to COVID-19 or the complications from severe disease.

Do I qualify for the third dose?

After completing the primary series, some moderately or severely immunocompromised people should get an additional third dose given 28 days after the second dose. A third dose of the Pfizer-BioNTech COVID-19 vaccine is approved for people ages 5 years and older who are moderately or severely immunocompromised. A third dose of the Moderna COVID-19 vaccine is approved for people ages 18 years and older who are moderately or severely immunocompromised. .

The following is a breakdown of the criteria established by the CDC to determine if you qualify as an immunocompromised individual.

People with medical conditions or people receiving treatments that are associated with moderate to severe immune compromise as follows:

  • Receiving active cancer treatment for tumors or cancers of the blood
  • Received an organ transplant and are currently taking medicine to suppress the immune system
  • Received a stem cell transplant within the past two years or are currently taking medicine to suppress the immune system
  • Moderate or severe primary immunodeficiency (such as DiGeorge syndrome or Wiskott-Aldrich syndrome)
  • Advanced or untreated HIV infection
  • Active treatment with high-dose corticosteroids (greater than 20 milligrams of prednisone or equivalent per day), biologic agents or other drugs that may suppress your immune response
  • Other conditions that cause moderate or severe immunosuppression similar to the above conditions

We encourage you to talk with your healthcare provider about your medical condition to see if getting an additional dose is appropriate for you.

Do I qualify for the booster dose?

The FDA and CDC approved COVID-19 vaccine booster shots for everyone 18 years or olderat least five months after receiving their second dose of the Pfizer or Moderna vaccine series and two months after receiving the single dose of the Johnson & Johnson vaccine. On Jan. 5, The Centers for Disease Control approved a booster of the Pfizer COVID-19 vaccine for children ages 12-17 five months after their initial Pfizer-BioNTech vaccination series.

What booster dose should I receive?

Eligible individuals may choose which vaccine they receive as a booster dose. Some people may have a preference for the vaccine type that they originally received, and others may prefer to get a different booster. If a patient prefers to receive a booster dose that is different from their original COVID-19 vaccine series, federal and state regulatory agencies support this choice.

What is the process for scheduling an appointment?

If you qualify as an immunocompromised individual or fall in the eligibility criteria for a booster shot, you can schedule your vaccine appointment today through MyOchsner or by calling 844-888-2772. Ochsner Health is administering third dose and booster shots to individuals at our regularly scheduled vaccination events across the state.

When you log in to MyOchsner, you will choose “Schedule an Appointment.” Then click the tile/button labeled “COVID Vaccine + Booster.”

Those who do not have a MyOchsner account can sign up at Appointments are encouraged, but walk-ups are welcome.

Increasing vaccinations bring us closer to reaching the threshold of vaccinated Louisianans and Mississippians needed to slow the spread and put an end to community transmission. It will take all of us working together to educate, encourage and persuade more of those living in our communities to get vaccinated. The key to ending this pandemic is at our fingertips, and your hard work and dedication make a difference.

For more information on the COVID-19 vaccine, please visit:

Editor's note: This blog was originally published on Oct. 5, 2021 and has since been updated. 

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