The Food and Drug Administration told makers of experimental COVID-19 vaccines that, in order to request emergency approval, they need to provide at least two months of follow-up data after trial participants received their final injection.

The new requirement –­­ listed within the agency's newly published guidelines for Emergency Use Authorization (EAU) –­­ creates an unlikely timeline for drugmakers to receive approval by Nov. 3.

FDA SET TO ANNOUNCE GREATER RESTRICTIONS FOR COVID-19 VACCINE: REPORT

As part of its updated requirements, the FDA noted that vaccine makers should follow participants for a minimum of two months after receiving their final dosage in an effort to rule out any major side effects before submitting candidates for EAU approval.

This data will help to "provide adequate information to assess a vaccine’s benefit-risk profile including adverse events; cases of severe COVID-19 disease among study subjects; and cases of COVID-19 occurring during the timeframe when adaptive (rather than innate) and memory immune responses to the vaccine would be responsible for a protective effect," the guidelines state.

TRUMP ADMINISTRATION TO BLOCK FDA GUIDELINES THAT COULD DELAY CORONAVIRUS VACCINE: REPORT

The requirements are aimed at companies seeking rapid approval through the FDA’s emergency authorization pathway. That accelerated process, reserved for health emergencies, allows medical products onto the market based on a lower bar than traditional FDA approval.

(iStock)

(iStock)

But the FDA has made clear only vaccines that are shown to be safe and effective will be authorized for coronavirus.

Dr. Peter Marks, director of the FDA's Center for Biologics Evaluation and Research, said in a statement that "being open and clear" in this guidance is "critical to building public confidence and ensuring the use of COVID-19 vaccines once available."

Marks said the FDA's new guidance on emergency use authorization underscores that commitment "by further outlining the process and recommended scientific data and information that would support an emergency use authorization decision."

COVID-19 CASES, DEATHS SPIKING AS US REELS FROM SECOND WAVE OF VIRUS 

However, a senior administration official confirmed Monday that the White House had blocked the FDA’s plans to formally publish the safety guidelines regarding the two-month data requirement, arguing there was “no clinical or medical reason” for it.

However, this didn't stop the agency, which posted the guidance on its website a day later, making clear that regulators plan to impose the safety standards for any vaccine seeking an expedited path to market.

President Trump has repeatedly insisted a vaccine could be authorized before Nov. 3. and even noted this week that vaccines are coming “momentarily,” in a video recorded after he returned to the White House.

The Associated Press contributed to this report. 

CLICK HERE TO GET THE FOX NEWS APP