"a massive blow to confidence in the agency's ability to regulate vaccines" (BioCentury)
In early September, two senior FDA officials resigned suddenly, without any sort of public statement or succession plan, as reported by BioCentury.
Marion Gruber, director of FDA's Office of Vaccines Research & Review (OVVR) as well as her deputy, Dr. Philip Krause, both resigned in the wake of the controversial decision by the Biden Administration to push a third round of Covid-19 "Booster Shots".
To date, neither Gruber or Krause have made statements on exactly why they left but there has been much speculation.
Science Doesn’t Support Third Shot, Say Officials Who Left FDA in Spat With Biden Over Boosters - Defender
"2 top FDA officials resigned over the Biden administration's booster-shot plan, saying it insisted on the policy before the agency approved it, reports say" - Business Insider
FDA officials reportedly resign over Biden administration booster-shot plan
On August 12th, health officials authorized a third booster shot. Dr. Jesse Goodman, a former chief scientist with the FDA stated,
"Normally, what you do is lay out the data first, and then say how the data supports the decision. When the White House made its announcement on booster shots, it did essentially the opposite. This was a serious mistake in how it was handled."
The White House was warned by federal health officials on September 3rd, that there still isn't enough data to ethically recommend boosters for all adults.
While FDA doesn’t have to follow its advisers’ recommendations, it generally does — except this time around is unlike any other. Today is the day that top health officials and President Joe Biden said that broad booster rollout would begin. That vaccine experts and some FDA regulators themselves don’t believe it’s the right time for most adults, throwing another wrench in the Biden administration’s vaccine messaging. (Politico)
Essentially, the FDA and even the openly-corrupt CDC, recommended against the rush to authorize booster shots, yet the White House plowed forward, causing worries throughout the medical community that health care providers may be putting themselves at risk by immunizing patients outside the FDA and CDC recommendations, according to ACIP's Helen Keipp Talbot.
The fact that the Biden Administration pushed forward anyway in this regard is likely the main reason for the resignation of Gruber and Krause. FDA senior officials don't just resign unexpectedly in normal scenarios.
On top of all that, drug company officials have stated that they fully expect their COVID shots will turn into an annual requirement as the pandemic morphs into a "perennial endemic". (The Intercept 3/18/2021)