by Delilah Newton | Sep 01, 2021

What’s the difference between an additional (third) dose and a booster dose?
Sometimes those with compromised immune systems do not build adequate or lasting protection from the virus, especially variants. When this happens, getting another dose of the vaccine can sometimes help them build more protection against infection and disease. Therefore, the CDC recommends moderately to severely immunocompromised people consider receiving an additional (third) dose of an mRNA COVID-19 vaccine (Pfizer or Moderna) at least 28 days after the completion of the initial two-dose series. This option is currently approved and available to those individuals. Physicians should notify their patients that meet this criteria and likewise, patients who are wondering if this applies to them, should discuss a third dose with their primary care office.

A “booster dose” is another dose of a vaccine that is given to someone who built enough protection after initial vaccination; however, that protection has decreased over time (also called waning immunity). Because of the continued spread of COVID-19 and the highly contagious Delta variant, booster doses are recommended to prevent waning immunity in vaccinated individuals. They are expected to be available in the fall of 2021.

Who should get a third dose of the vaccine?
Currently, individuals with moderately to severely compromised immune systems are recommended for a third dose of COVID-19 vaccine. This includes people receiving treatment for cancer, people taking medications that weaken the immune systems, organ or stem cell transplant recipients, individuals with advanced or untreated HIV infection, and other conditions. If you are unsure if you are recommended for a third dose, talk with your health care provider. The third dose of COVID-19 vaccine can be given anytime 28 days after receiving the second dose.

Can I get any type of COVID-19 vaccine for the third dose?
No. You should receive the same brand of vaccine you received for your first and second doses, either Moderna or Pfizer.  

*Please note, at this time third dose and booster shots are not available to those who received the Johnson & Johnson one-dose vaccine. More information will be shared as it becomes available.

Who should get a booster shot and when?
The latest information states that state health officials are prepared to offer booster shots for people in the U.S. by late fall and starting eight months after an individual’s second dose, likely in accordance to the original role out, by infection risk and age factors. More information will be shared as it becomes available.

Learn more and get the most up-to-date information at

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