A Centers for Disease Control and Prevention (CDC) advisory panel in the US on Thursday voted to recommend a third Pfizer-BioNTech Covid-19 shot for those over 65 and certain groups with underlying medical conditions.

In a series of votes, the Advisory Committee on Immunization Practices said it favored of booster shots at least six months after the standard two-dose regimen for all people 65 years old and older, as well as those 18 to 64 with underlying medical conditions that put them at high risk for Covid-19

Long-term care facility residents also were included.

The panel voted against allowing the booster shots for those with frequent occupational and institutional exposure to the virus, such as healthcare workers.

The votes came after hours of meetings, which began Wednesday and included discussions about the efficacy of the Pfizer Covid-19 vaccine over time and the necessity of a booster.

The US Food and Drug Administration gave its full approval Wednesday for booster shots along the same guidelines, but added those with occupational and institutional exposure.

The FDA and CDC’s guidelines and recommendations have so far derailed the Biden administration’s desires to begin offering booster shots to nearly everyone this week.

The full CDC must give its final approval before booster shots for the affected groups can start to be administered.

Last week, a group of FDA scientists said a third dose of Pfizer’s vaccine likely increases antibodies in recipients and offers greater protection against Covid-19. However, they stopped short of saying the extra dose is needed by a majority of Americans.

They said that even with waning immunity over time, the two-shot regime of the Pfizer vaccine still largely protects against severe cases of Covid-19.