represents a critical milestone in our journey to deliver a COVID-19 vaccine to the world and we now have a more complete picture of both the efficacy and safety profile of our vaccine, giving us confidence in its potential," Pfizer CEO Albert Bourla said in a statement.

Moderna, another pharmaceutical company, announced Monday that early clinical trial results show its vaccine is 94.5% effective.

The agency could make a decision at the end of the meeting on December 10 about whether to issue an emergency use authorization, the source said.

"It will make sense that in all likelihood the FDA will consider both applications together," the source said, considering that both the Pfizer and Moderna vaccines use the same technology and appear to have very similar safety and efficacy results from their large-scale clinical trials.

If the FDA authorizes the vaccines, they can then be immediately distributed to states, according to a presentation made last month at the US Centers for Disease Control and Prevention.

However, no one can be vaccinated until a CDC advisory committee reviews the data, recommends the vaccine, and decides which groups will receive it first.

If the FDA authorizes the vaccines, the CDC's Advisory Committee on Immunization Practices, an independent panel of experts, will meet within 24 to 48 hours, according to a CDC spokesperson.

At that meeting, the committee will determine if everyone should get the vaccine, or if some people should be excluded.

"We have all been alerted on ACIP we should be very flexible with our calendars because it's likely there won't be a lot of advanced notice given for this meeting.

William Schaffner, a committee member, told CNN this week.

Once ACIP issues its recommendations, vaccinations can be given.

"We have a plan in places that the moment that the FDA concludes that that vaccine is safe and effective, we have a system in place to begin within 24 hours to ship that to hospitals and health care officials and 24 hours after that injecting that vaccine into Americans," Vice President Mike Pence said during a White House Coronavirus Task Force briefing on Thursday.

States are currently working out the details of running vaccination clinics.