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In-Depth: 3rd vaccine dose vs vaccine booster; what's the difference and why is it important

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Posted at 4:32 PM, Aug 13, 2021
and last updated 2021-08-17 08:44:21-04

NASHVILLE, Tenn. (WTVF) — Beginning Tuesday, Metro Health will offer a third dose of the COVID-19 vaccine for people who are immunocompromised, and it's important to remember there is a difference between a booster shot and the third dose.

The third dose is exactly that - it is an additional dose of the vaccine as part of the primary sequence for some immunocompromised individuals to help them mount an immune response similar to what most people get with just two doses.

The CDC’s Advisory Committee on Immunization Practices (ACIP) unanimously recommended a third dose of the Pfizer and Moderna COVID-19 vaccine for those weakened immune systems. The vote was made Friday following the authorization of the third dose by the FDA.

According to reports from the New York Times and Washington Post, the Biden administration is poised to announce that many Americans will need a booster shot.

Two administration sources told the New York Times that Americans will be asked to get a booster shot eight months after they were fully vaccinated. The first doses of the booster shot are expected to be administered in September, according to the Washington Post.

A booster dose is supplemental and given to people whose immune response has weakened over time. The dosage may be different than what people first received.

Immunity from some vaccines can wear off, and at that point, a “booster” dose is needed to bring immunity levels back up, according to the CDC. A booster dose usually occurs several years after the initial series of vaccine doses is given.

For example, in the case of the DTaP vaccine, which protects against diphtheria, tetanus and pertussis, the initial series of four shots that children receive as part of their infant immunizations helps build immunity. But a booster dose is needed at 4 years through 6 years old. Another booster against these diseases is needed at 11 years or 12 years of age. This booster for older children—and teens and adults, too—is called Tdap.

Visit the CDC's website to learn more about how vaccines work.