A Centers for Disease Control and Prevention advisory group met Monday to debate whether or not eligible Americans should receive a COVID-19 booster shot.

The CDC’s Advisory Committee on Immunization Practices meeting came as an independent panel of experts advising the CDC recommended the use of the Pfizer COVID-19 vaccine for people 16 years and older under full FDA approval.

A pharmacy technician loads a syringe with Pfizer's COVID-19 vaccine at a mass vaccination site at the Portland Expo in Portland, Maine. (AP )

Monday’s panel set out to discuss a framework for a possible third jab of the vaccine. Its use, they said, would be needed in one of two scenarios: when the initial immune response from the first of two vaccine doses is insufficient or when the initial immune response wanes over time.

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The panel noted that it is not uncommon for some diseases to require more than two vaccine doses – as has been the case with COVID. Hepatitis B and HPV, for instance, require a third jab at least six months after the second dose.

Still, the ACIP reached no definitive conclusion and will meet again in mid-September.

The debate among health officials over a third vaccine dose continues. U.S. health officials announced earlier this month plans to dispense COVID-19 booster shots to all Americans to shore up their protection amid the surging delta variant and signs that the vaccines’ effectiveness is slipping.

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Laboratory blood tests have suggested that antibodies – one of the immune system’s layers of protection can wane over time. It does not necessarily mean that protection disappears altogether, but that it is not as strong or that it could take longer for the body to fight back against an illness.

The Associated Press contributed to this report.