Scientific experts at the U.S. Food and Drug Administration have voted overwhelmingly against Pfizer's application for a third shot of its COVID vaccine for those aged 16 and above, posing as a major roadblock to President Joe Biden's plans for a vaccine booster program.

The FDA vaccine advisory committee voted 16 to 2 on Friday against recommending the booster shot of the two-dose Pfizer vaccine, which was the first vaccine in the U.S. to gain approval from the FDA.

According to Faithwire, panel members at Friday's discussions spoke about how a COVID vaccine booster shot may help older, immunocompromised individuals, but argued against the same for a younger set due to the lack of evidence to suggest otherwise. Moreover, there were concerns about the increased risk of heart inflammation among those who chose to get the initial shots, especially among younger males, with whom the side effect was commonly seen.

Fox News reported that the FDA panel was responsible for determining whether the data from Pfizer's clinical trial would support the approval of the booster shot of Comirnaty, which is now the name of the brand's COVID vaccine following its FDA approval.

The committee was composed of members of the FDA's Vaccines and Related Biological Products Advisory Committee (VRABPAC), the Centers for Disease Control and Prevention (CDC) officials, Israel's Health Ministry, vaccine experts and Pfizer representatives.

Pfizer is awaiting final review from the FDA, after which the CDC's Advisory Committee on Immunization Practices (ACIP) will meet on Wednesday to determine who should get the third COVID vaccine shot and when. Pfizer said it would continue to work with the vaccines committee to address any concerns and that it stood by its belief that boosters can help the broad population, the Financial Times reported.

"These data, and the larger body of scientific evidence presented at the meeting, underscore our belief that boosters will be a critical tool in the ongoing effort to control the spread of this virus," Pfizer's head of vaccine research development Kathrin Jansen said.

Meanwhile, infectious diseases expert Dr. Anthony Fauci took an interesting stance after the FDA panel overwhelmingly voted against the COVID vaccine booster shots for most Americans, saying on Sunday that "I don't think they made a mistake."

However, the White House chief medical adviser reassured the public that he would support a third dose if the data shows that it will continue to be effective in protecting against COVID, CNBC reported. He added that right now, the priority of the administration is to convince the unvaccinated to get the COVID jab. The FDA panel's decision comes just a couple of weeks after President Biden said that boosters will be made available to all Americans beginning September 20.

On September 9, President Biden spoke about how COVID vaccine boosters "give you even more protection than after your second shot," saying that the U.S.' "top government doctors...believe that a booster is likely to provide the highest level of protection yet."

He also tasked the FDA and CDC to determine "which booster shots to give, when to start them, and who will give them" but assured that the U.S. has "bought enough boosters - enough booster shots - and the distribution system is ready to administer them."