In the midst of a vaccine booster shot rollout, the FDA’s two highest-ranking vaccine research officials are stepping down from their positions. Sources say it’s because they don’t think President Biden is following the science when it comes to booster shots for the COVID-19 vaccine.

The two people leaving are Marion Gruber, the director of the FDA’s Office of Vaccine Research, and Review and her deputy, Phil Krause. Together the pair have more than 40 years of experience at the FDA. 

According to BioCentury, the outlet that broke the news, a source close to the pair says one of the reasons the pair is leaving is the COVID-19 vaccine booster shots the Biden administration is now recommending, if the FDA approves them. 

A reporter with the biomedical outlet EndPoints News called the resignations a “red alert”.

Oh man. Red alert. 2 of the most senior vaccine leaders at FDA are stepping down. https://t.co/4DktoyFXFn

— Zach Brennan (@ZacharyBrennan) August 31, 2021

BioCentury’s reporting says the pair didn’t think there was enough research to justify booster shots yet. It went on to say they took Biden’s announcement as a way to pressure the FDA into authorizing them. 

“Earlier today, our medical experts announced a plan for booster shots to every fully vaccinated American — adult American,” Biden announced on August 18. “Pending approval from the Food and Drug Administration and the CDC’s Committee of outside experts, we’ll be ready to start these booster — this booster program during the week of September 20.”

In an interview with CBS on September 5, Dr. Anthony Fauci, the Chief Medical Officer to the President, said they may not reach that target date.

“We’ve said right from the very beginning, we’re not going to do anything unless it gets the appropriate FDA regulatory approval,” Dr. Fauci said. “And then the recommendation from the Advisory Committee on Immunization Practices. Looks like Pfizer has their data in, likely would meet the deadline. We hope that Moderna would also be able to do it so we could do it simultaneously, but if not, we’ll do it sequentially.”

In that same interview, Fauci said part of the delay is making sure the boosters are safe.

“You want to make sure when you’re dealing with allowing the American public to receive an intervention, you want to make sure you are absolutely certain,” he said. “The other is the immunogenicity or efficacy. Immunologists would predict it would be protective.”

The other issue is whether or not it is effective. Scientists in Israel are researching the effectiveness of the two and three dose Pfizer vaccines. Their research found that the protection against viral load started going down after two months of Pfizer’s second dose, followed by a complete reduction after 6 months.

Gruber and Krause will be leaving in October and November. Dr. Peter Marks, the FDA’s director of the Center for Biologics Evaluation and Research, will serve as the acting director of the vaccines office. 

Dr. Luciana Borio, the former FDA Acting Chief Scientist, responded on social media.

@US_FDA is losing two giants who helped bring us many safe and effective vaccines over decades of public service. https://t.co/hkLJPDo2HK

— Luciana Borio, MD (@llborio) August 31, 2021

A spokesperson for the FDA issued a statement about the resignations, saying the FDA is “confident in the expertise and ability of our staff to continue our critical public health work.”