The third dose: What's the difference between a 'booster shot' and an 'additional dose?'

COVID-19 booster shots now being given
Posted at 8:09 PM, Aug 18, 2021
and last updated 2021-08-18 21:15:49-04

The Corpus Christi-Nueces County Public Health District held a mass-vaccination event Wednesday, which offered the area's first "additional dose" of the Moderna and Pfizer vaccines.

Also Wednesday, the Centers for Disease Control issued a statement encouraging people to get a "booster shot" beginning Sept. 20.

Additional dose? Booster shot? What's the difference? Aren't they the same thing?

Corpus Christi-Nueces County Public Health Director Annette Rodriguez said the key difference between the two phrases is who is able to receive which dose/shot.

First, it's important to know that the vaccine's third dose, be it Moderna or Pfizer, will be the exact same formula given in the first two doses. Rodriguez said there's no difference between the three shots.

However, only people with weakened immune systems were eligible for "additional doses" distributed at events such as Wednesday's -- people such as cancer patients, transplant recipients or patients taking immunosuppressants, according to the CDC.

Because these patients' immune systems don't allow their bodies to fully benefit from the vaccine the way a healthy person's would, the immunocompromised are being prioritized in the same way they were for the first and second doses.

Healthier people will be eligible for September's "booster shots" eight months after getting their second dose.

While the immunocompromised need the third dose of a vaccine because their own bodies need help supporting the previous doses, healthy people are being advised to get a booster in order to support the vaccine itself. When the COVID-19 vaccines were given emergency-use approval by the FDA, it was never clear exactly how long the drugs' protection would last, so the booster adds an extra layer of protection to help support the previous doses.

Keep in mind, whether a patient is eligible for an additional dose or a booster shot, they were only being offered for mRNA-based vaccines. People who were given the Johnson & Johnson vaccine are not yet eligible.