It’s A Matter of Why: COVID-19 Third Dose vs. Booster Explained

As we continue to face and battle COVID-19 as a nation, patients are asking additional questions relating to booster shots.

While the concept is not easily understood for some patients, the actuality is that the idea is, in fact, just that simple. Both shots are intended to help reduce the risk of contracting COVID-19; the main difference is not in what the doses are made up of, instead, how and why they are being administered.

Our Medical Director, Dr. Chow, met with our team to share more.

How Does A Third Shot Differ From a Booster?

“Patients who may receive a third shot imply that the first two shots did not build sufficient immunity due to their immunocompromised state (weakened immune system). This means these patients did not gain the desired level of effectiveness from the first two shots, requiring an additional dosage to help build that immunity,” said Dr. Chow.

Patients need to remember that the COVID-19 continues to change and mutate over time, making a vaccine less effective, requiring additional dosage.

According to Johns Hopkins Medicine, severely immunosuppressed patients should receive a third shot:

What Makes a Booster … well, Boost?

“Receiving a booster suggests that a patient’s first series of shots were effective. However, like many things, the antibody levels wane, and the protection diminishes over time. The booster is there to “boost” the diminishing levels of the antibodies to continue to help protect from COVID-19,” said Dr. Chow. While a booster sometimes is an exact replica of the initial vaccine, it also can be modified to better protect against variants.

According to the Center for Disease Control Prevention, COVID-19 Vaccine booster shots are available for the following Pfizer-BioNTech vaccine recipients who completed their initial series at least six months ago and are:


Dr.Chow - AccessNurse Medical Director

More About Joseph Chow, MD, MBA – AccessNurse Medical Director

Dr. Joseph Chow is AccessNurse’s Adult Medical Director and is responsible for clinical oversight of the call center and clinical staff. He also provides executive guidance to the clinical risk management programs and serves on AccessNurse’s Quality Insurance Committee, where he oversee

s all call center quality improvement initiatives. Dr. Chow joined TeamHealth in 2012 and received the TeamHealth Urgent Care Medical Director of the Year award the following year. He serves on TeamHealth’s Patient Safety Organization Board of Directors and is an elected President of the board for the Urgent Care Association 2021-2022.