By Rosa Flores and Sara Weisfeldt, CNN

(CNN) -- Those who showed up to a Miami vaccination site on Wednesday found themselves in the rare position where they got to choose which Covid-19 vaccine they would like to get: the newly FDA-approved Johnson & Johnson vaccine, or the Pfizer vaccine.

The long-awaited, one-dose J&J vaccine became available in the United States this week after the US Food and Drug Administration gave it emergency use authorization last Saturday.

Made by Janssen, J&J's vaccine arm, the vaccine is safe and effective, and it's considered flexible. It's a single dose, and it doesn't require special storage. The vaccine is authorized for people ages 18 and older.

However, there has been concern that because the public has heard that the shot is only 72% protective in the US, and the Pfizer and Moderna Covid-19 vaccines are about 95% protective, some will think this is a "second class" vaccine. Experts say those numbers are highly misleading -- and urge people to take whatever shot is first available to them.

Gov. Ron DeSantis issued an executive order this week that expanded access to the vaccine to people 50 and over who are K-12 school personnel, firefighters and law enforcement officers.

So far, more than 3.1 million Floridians have received one or both doses of a vaccine, according to state records. An overwhelming majority of the recipients have been seniors age 65 and older.

Florida's four FEMA-supported vaccination sites -- in Tampa, Orlando, Jacksonville and Miami -- are now allowing people to choose between J&J and Pfizer, according to Jason Mahon, communications director for the Florida Division of Emergency Management.

"Giving them the choice was important," Mahon told CNN.

Those at the Miami-Dade College vaccination site on Wednesday mulled over their options before deciding which shot they wanted administered.

Some said they chose the J&J vaccine because they wanted to get one shot rather than two (which both Pfizer and Moderna require).

Lolita White told CNN that she is "afraid of needles" and therefore can "only do this once."

"It was liberating," she said about getting the J&J vaccine. "But it was very scary at the same time because ... I'm definitely afraid of needles. The people in there were very supportive. The guy who gave me the shot ... said don't be afraid."

Despite J&J's lower efficacy, White said she was comforted to learn that J&J's research included protection against the new variants of the Covid-19 virus.

Guillermo Muñoz said he trusts that all the vaccines are effective -- but he also preferred getting the J&J vaccine because it required one dose.

"I want to make sure that I'm protected and I want to make sure that, you know, that we protect others," Muñoz told CNN. "The quicker we reach herd immunity, the quicker we will be able to go back to as normal a life as we possibly can."

Others said they prefer Pfizer -- citing various reasons, including that it's been available longer.

"I just don't know much about it (J&J vaccine), so I would rather go with something that's well known," Rocio Mendez told CNN.

Ruth Watkins also opted for Pfizer -- she said she believes in the company so much that she decided to invest in it.

"I don't choose to buy Johnson & Johnson products and haven't for a really long time," Watkins told CNN. "And Pfizer was just a good choice."

Anthony Fauci, the nation's top infectious disease expert, urged Americans to take any of the three "highly efficacious" coronavirus vaccines now available to them and not delay getting one vaccine over another.

"If I were not vaccinated now and I had a choice of getting a J&J vaccine now or waiting for another vaccine, I would take whatever vaccine would be available to me as quickly as possible for the simple reason of what I said a moment ago," he told CNN's Dana Bash on "State of the Union" on Sunday.

"We want to get as many people vaccinated as quickly and expeditiously as possible."

Patricia Gibbs, who got the Pfizer booster shot on Wednesday, echoed Fauci's opinion.

"We all need to get this shot to protect everybody," Gibbs said.