On Friday, a Food and Drug Administration advisory committee voted unanimously to recommend that the agency should approve boosters of the Johnson & Johnson single-shot COVID-19 vaccine.

The Vaccines and Related Biological Products Advisory Committee's unanimous vote is a key step in letting booster shots of the single dose-vaccine into American's arms, according to CNBC.

The panel is recommending the boosters to Americans 18 and older, to be administered at least two months after they received their initial dose. More than 15 million Americans received this vaccine.

Like past votes, the FDA usually follows the advice of the advisory committee, with the potential for the final decision to come within days. Following that decision, a Centers for Disease Control and Prevention vaccine advisory group will decide next week who will be eligible for boosters of the J&J vaccine.

"If it issues a recommendation and CDC Director Dr. Rochelle Walensky signs off, booster shots could begin immediately," according to CNBC.

J&J has submitted data showing that a booster shot greatly increases the vaccine's protection against symptomatic infection, from 72 percent to 94 percent, when administered two months after their first dose.

FDA scientists published an analysis of J&J's application for a booster just days before Friday's meeting, questioning the data presented by the company.

"The FDA said people may benefit from a second dose, but added the information provided by the company was limited and the agency hadn't verified all of it yet. It acknowledged a single J&J dose was consistently less effective than the mRNA vaccines in clinical trials and in real-world studies," wrote CNBC.

According to CNBC, many of the committee members said that the vaccine should be administered in two doses, like its Pfizer and Moderna counterparts.

Some committee members also asked the FDA whether they could postpone a decision on booster before the vote, saying it may be too early as there are still a number of questions remaining.

"Is there an option of saying it's a little early? There are a number of issues that are still outstanding," said Dr. Cody Meissner of Tufts University. "There are a lot of uncertainties, at this point, making it hard to vote for or against this tonight."

Although committee member Dr. Michael Nelson said J&J's data was "a little bit immature and somewhat scant in multiple areas," he said he thought the safety and efficacy data the company had so far was enough to support emergency use.

"I certainly agree with my colleagues that this does look more like a two-dose vaccine," Nelson said.