So I'm told there's going to be 225 people vaccinated today. Can you walk me through the process?

So the patient comes. We ask them if they're well today. We check if they have any allergies.

Betsy and N. Correspondent Ivana Kotasava. She's speaking with Nurse Sharon Chapman in a vaccination center set up in Cardiff Wales.

This is where yesterday some of the very first people in the world got the Pfizer-Biontech COVID-19 vaccine.

Have you vaccinated anyone yet this morning? How many people? I think I'm five.

Five. And what was the reaction? I mean, people were just really pleased to have had no nervousness.

What do you think you'll be able to get one this week? Oh yeah, are you excited? Absolutely. Are you nervous at all? No, no. Bring it on.

Yesterday the United Kingdom became the world's first nation to begin administering a fully authorized and vetted vaccine.

This is a pretty historic moment. And as you could hear, there was a lot of excitement.

Ivana watched as health care workers prepped the vaccine on site, deluding it, and then preparing the individual doses.

Most people got this first dose in their left arm. And Ivana says that her site, they were monitored for 15 minutes afterwards to make sure they didn't develop any immediate side effects.

Back in the United States, we are now edging closer to our own authorization of a vaccine.

An advisory committee for the Food and Drug Administration will consider recommending emergency use authorization for the Pfizer and Biontech vaccine candidate on Thursday.

This week, additional data from the clinical trials was released to the public. And I've had a chance now to review that information.

It confirms that the vaccine is 95% effective at preventing COVID-19 and suggests that even just the first dose of the vaccine could offer some protection.

So what is going to happen next? I sat down with the Commissioner of the FDA yesterday, Dr. Stephen Hahn, to try and find out.

I'm Dr. Sanjay Gupta, CNN's Chief Medical Correspondent. And this is coronavirus, fact versus fiction.

Well, sir, it's been a busy year, obviously, and a busy couple of days, even.

A lot of people have heard the news about these vaccines, Pfizer's and Moderna specifically. Is it pretty much a foregone conclusion at this point that they will be authorized at least under emergency use?

Well, I'm not going to prejudge the decision making of our career scientists, nor of the vaccine and related biologic advisory committee.

As you know, we have a process, and this is a very rigorous process to establish the safety and efficacy of a vaccine. Our team has done their initial analysis.

And we do feel that preliminarily that the success criteria have been met that's been reported in the press today.

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