Federal regulators are warning the Bide Administration they should push back its plan to start administering COVID-19 booster shots by September 20 to give researchers more time to do their due diligence.

Dr. Janet Woodcock, the acting commissioner of the Food and Drug Administration, and Dr. Rochelle P. Walensky, who heads the Centers for Disease Control and Prevention, both told the White House on Thursday that their agencies very likely will only have enough collected research by that date to be able to recommend boosters just for recipients of the Pfizer-BioNTech vaccine. They even cautioned that they may only have enough reliable data to recommend boosters for certain persons who took the two-dose Pfizer vaccine.

It’s the latest complication for President Biden’s plans to accelerate the distribution of the booster shots. Experts have said that as the efficacy of the coronavirus vaccines wane, booster doses will be necessary to maintain the high levels of protection the vaccines offer against severe COVID symptoms, hospitalizations and death. It’s all happening as the highly-transmissable delta variant of the virus has sparked a new surge, overloading hospitals with sick patients, and causing 1,500 deaths per day.

Here’s what the New York Times wrote about the meeting between the heads of the two key federal health agencies and the White House:

The two health leaders made their argument in a meeting with Jeffrey D. Zients, the White House pandemic coordinator. Several people who heard about the session said it was unclear how Mr. Zients responded. But he has insisted for months that the White House will always follow the advice of government scientists, wherever it leads.
Asked about the meeting, a White House spokesman said on Friday, “We always said we would follow the science, and this is all part of a process that is now underway,” adding that the administration was awaiting a “full review and approval” of booster shots by the F.D.A. as well as a recommendation from the C.D.C.

White House spokesperson Chris Meagher followed up on that by reiterating that the administration will defer to health experts before it gives the go-ahead on boosters.

“When that approval and recommendation are made, we will be ready to implement the plan our nation’s top doctors developed so that we are staying ahead of this virus.”

Biden announced several weeks ago that, contingent on the FDA’s authorization, booster shots would start to be given out September 20 to adults who had received their second dose of the Pfizer or Moderna vaccine eight months ago.

But the deadline was seen by some health authorities in the government as unreasonable, given that researchers still were analyzing the data to make the final determination. In fact, two top officials at the FDA are reportedly quitting in the coming weeks over the way the booster program has been handled.

Researchers simply don’t have anywhere near the same amount of data on the Moderna vaccine or the Johnson & Johnson single-dose inoculation, compared to the Pfizer shot. More than 211 million doses of the Pfizer vaccine have been administered in the U.S.; 146 million shots of the Moderna have been distributed; 14 million doses of the J&J have gone out.