Marion Gruber and Phil Krause, two of the Food and Drug Administration's top vaccine reviewers, are leaving the agency, the regulator confirmed on Tuesday.
In a letter sent to agency staff and obtained by BioPharma Dive, Peter Marks, director of the agency's Center for Biologics Evaluation and Research, said both plan to step down from the FDA within the next two months.
Gruber, an FDA veteran for three decades and the director of its vaccine review office, will retire on Oct. 31. Krause, the vaccine team's deputy director, will leave the agency in November, Marks said.
"Thank you so much to Marion and Phil for all that they have contributed and continue to contribute to the agency," Marks wrote, adding that the search for the next vaccine office director "will begin imminently."
Marks didn't say why Gruber and Krause, who both played big roles in the review and authorization of three coronavirus vaccines over the past year — and recently, the full approval of Pfizer's shot — have suddenly decided to step aside. An FDA spokesperson only said the regulator is "confident in the expertise and ability of our staff to continue our critical public health work, including evaluating COVID-19 vaccines." The spokesperson did not clarify further in response to follow-up questions from BioPharma Dive.
Nonetheless, the surprise development, first reported by BioCentury on Tuesday, comes at a critical time for the FDA's vaccine review team. The FDA is now weighing whether to authorize a potential third Pfizer shot for most Americans, and could soon evaluate the use of coronavirus vaccines in children.
The White House announced plans to begin administering boosters the week of Sept. 20, a debated decision that got ahead of the completion of the FDA's own review. The Biden administration drew criticism for the public announcement, which puts considerable pressure on the regulator to clear boosters in time for the planned rollout despite lack of definitive proof they are needed broadly for healthy adults.
Senior health officials have argued that accumulating evidence shows a waning effect in vaccinated individuals, and that boosting their levels of neutralizing antibodies through a third shot could strengthen protection. They've also said their intent in announcing plans ahead of FDA authorization and the backing of federal vaccine advisers was to help states and counties prepare for administering booster shots. Both FDA and CDC leaders signed off on a White House announcement in August.
Pfizer has since filed for approval of a booster, completing its application last week. But the review of that application will now take place without Gruber or Krause, a loss for the agency's efforts to rapidly assess the submitted data.
The FDA "is losing two giants who helped bring us many safe and effective vaccines over decades of public service," tweeted Luciana Borio, a former chief scientist with the agency.
Both Gruber and Krause were important players, for instance, in establishing the guidelines Pfizer, Moderna and Johnson & Johnson had to abide by to win emergency clearance of each of their vaccines.
Reviewing each shot under the emergency pathway — a regulatory tool reserved for a public health crisis — required the FDA to move as quickly as possible to get the vaccines to market without compromising its standards.
Gruber and Krause were also vocal participants in the public meetings to review the emergency applications from each developer, chiming in to settle scientific disputes among outside reviewers and clarify the agency’s position.
Their sudden and near concurrent departures could raise questions about the impact political pressure, now spanning two administrations, is having on the agency.
"These two are the leaders for biologic (vaccine) review in the U.S.," tweeted Rick Bright, the former director of the Biomedical Advanced Research and Development Agency. "They have a great team, but these two are the true leaders of CBER. A huge global loss if they both leave."
Note: This story has been updated to include additional detail and reference to comments from an agency spokesperson.