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 head 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.
Marks called Marion's departure a "huge loss," citing her "immeasurable contributions" in his letter, which also thanked Phil for his commitment and effort during the COVID-19 pandemic. A search for the next vaccine office director "will begin imminently," according to Marks.
But 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, most recently, the full approval of Pfizer's shot, have suddenly decided to step down at around the same time.
An FDA spokesperson said only that 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.
In an email sent to CBER staff, acting FDA Commissioner Janet Woodcock affirmed her confidence in the team that will remain in place under the leadership of Marks, who will step in as acting director for the vaccine office.
"We have put together a plan that will allow us to continue prioritizing science, while meeting timelines that are important to ensuring the end of this devastating pandemic," she wrote.
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 FDA completing its own review. The Biden administration was criticized for the public announcement, which puts considerable pressure on the regulator to clear boosters in time for the planned rollout despite limited evidence they are broadly needed at this time for healthy adults.
Senior health officials have argued that accumulating data show a waning immune response in vaccinated individuals, and that boosting antibody levels via 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.
Asked by a reporter Tuesday on whether the resignations affect trust in the FDA, Jeffrey Zients, coordinator of the White House's COVID-19 task force pointed to the "strong leadership" from agency head Woodcock and from Marks.
Zients emphasized that the administration's plan for additional doses remains "pending FDA conducting an independent evaluation and CDC's panel of outside experts issuing a booster dose recommendation."
Note: This story has been updated to include additional detail and reference to an email from Janet Woodcock as well as comments by the White House's Jeffrey Zients.