Key roles within the federal health departments are increasingly being filled by high-profile vaccine critics, including some who worked in tandem with Health Secretary Robert F. Kennedy Jr. before he was confirmed.

Why it matters: It's still unclear how much these critics' very public stances will translate into concrete policy or whether they'll erect barriers for Americans who want to get certain vaccinations.

• Kennedy has said he won't take away anyone's vaccines, and hasn't announced plans to pull any from the market.
• But the questions about vaccine safety and efficacy, calls for new studies, and challenges to scientific consensus are certainly rising, including from political appointees and Kennedy-aligned members of federal advisory panels.
• Critics are warning these challenges could chill the development of new treatments and even prevent some products from coming to market.

The latest: The FDA announced Wednesday that Tracy Beth Høeg had been appointed acting director of the Center for Drug Evaluation and Research.

• Høeg has been instrumental in the agency's recent claims that COVID vaccines have killed at least 10 children, though it hasn't presented the evidence it used to make that determination.

HHS employees presented what experts say is misleading or inaccurate information about the hepatitis B vaccine yesterday to the CDC's vaccine advisory committee.

• Kennedy has also hired David Geier to examine old medical records in the Vaccine Safety Datalink, causing angst among the scientists who manage the database, as the NYT reported yesterday. Geier used the database decades ago to make claims linking vaccines and autism, which have been discredited.
• Acting CDC director Jim O'Neill has called for vaccine manufacturers to develop separate measles, mumps, and rubella vaccines to replace the combined shot.

What they're saying: Asked whether Kennedy's vow to not take anyone's vaccines away still stands, and whether that can be interpreted to mean no vaccines will be pulled from the market, an HHS spokesperson didn't answer directly.

• "HHS has not limited access to vaccines. We have restored [informed] consent and individual-based decision making," HHS communications director Andrew Nixon said.

Driving the news: The CDC's vaccine advisory committee spent yesterday discussing the safety and effectiveness of hepatitis B vaccines, but punted to today a vote on whether to drop its recommendation that every infant get the shot at birth.

• Public health experts have said there's no evidence of safety issues with the birth dose, and that delaying it increases the chances infants could contract the liver disease.
• But presenters before the committee made the case — refuted by the medical establishment — that the vaccines may lead to health issues down the road, and that they may be less effective if given right at birth.

The presenters included:

• Vicky Pebsworth, a committee member who works for an organization widely viewed as anti-vaccine.
• Cynthia Nevison, a climate researcher with ties to Kennedy's anti-vaccine group.
• Mark Blaxill, who has claimed without evidence that every child who takes vaccine is injured to some degree, per MS NOW.

Presenters during the second day of the meeting today will include Aaron Siri, a leading anti-vaccine lawyer who will brief the committee on the childhood vaccination schedule.

• Siri — whose views are widely discredited among the public health and scientific community — worked for Kennedy's presidential campaign and has filed more than a dozen petitions on behalf of private citizens requesting the government halt distribution of certain vaccines.
• He has claimed that "not a single routine childhood vaccine was licensed based on a long-term placebo-controlled trial."
• In contrast, former FDA commissioner and Pfizer board member Scott Gottlieb said yesterday on CNBC that "vaccines have been approved on the basis of the longest, largest studies that have ever been done."

Siri has also promoted a discredited study that "showed that the vaccinated children in the study suffered from numerous chronic health issues that did not plague the unvaccinated children in the study."

• When asked whether HHS shares Siri's views and why he was chosen to present, Nixon said: "ACIP is an independent advisory committee and the qualified members will use evidence, including those from expert presenters, to make their recommendations backed by gold standard science."

What we're watching: The promotion of COVID vaccine skeptics is one thing; the elevation of someone who has questioned the safety of all childhood vaccines is another, and drew the starkest criticism yet from at least one Republican.

• "Aaron Siri is a trial attorney who makes his living suing vaccine manufacturers. He is presenting as if an expert on childhood vaccines. The ACIP is totally discredited. They are not protecting children," Sen. Bill Cassidy, the chairman of the Senate health committee, posted on X.
• Siri responded by challenging Cassidy to a public vaccine debate and arguing that vaccine manufacturers regularly present to the advisory committee.
• "All individuals who present to ACIP are experts in their subject area," Nixon said.

Concern about the FDA's functioning is certainly not limited to its oversight of vaccines, but the agency's stance on vaccines became a bigger issue in the last week following top vaccine regulator Vinay Prasad's leaked internal memo to staff.

• The memo alleged without presenting evidence that the agency has determined COVID vaccines killed "at least" 10 children, and proposed stringent new criteria for bringing new vaccines to market.
• The memo prompted a highly unusual rebuke this week from a dozen former FDA commissioners and top officials, including Gottlieb and others who served in the Trump administration.

Between the lines: There were plenty of people who thought the elevation of widely respected oncologist Rick Pazdur to be the agency's top drug regulator a few weeks ago signaled a course correction after a tumultuous period for the agency.

• Instead, Pazdur this week said he's retiring, and the FDA announced Høeg's appointment.
• Høeg — a physician epidemiologist whose background is in sports medicine — was mentioned by name in Prasad's memo for her role in the agency's determination that COVID vaccines killed children.
• "For those worried about Prasad assuming control of CDER, selection of Høeg is close to a worst-case scenario, an abrupt reversal from the hope for stability following selection of Pazdur," TD Cowen analyst Rick Weissenstein wrote in a note about her selection.

What they're saying: "I think what they want is no new vaccines on the market," Gottlieb said yesterday on CNBC.

• The new framework proposed by Prasad will, in effect, prevent updates to flu and pneumococcal vaccines, he added.
• "Americans need to make a decision. Do they want access to the flu vaccine? Even if they choose not to take it, do you want it to be available or not?"

The other side: Anti-vaccine activists and other MAHA-aligned supporters have made no secret of the fact that they want some vaccines pulled from the market.

• Toby Rogers, an anti-vaccine critic who recently testified alongside Siri before the Senate Permanent Subcommittee on Investigations, said in public comments to the advisory committee yesterday that he believes hepatitis B vaccines "should be removed altogether from the CDC childhood schedule."
• Others have called for the removal of COVID shots from the market in the aftermath of Prasad's memo.

My thought bubble: There is certainly a huge difference between changing federal vaccine recommendations — which has a real-world effect but a comparably limited one — and making decisions that would keep vaccines from people who want them.

• That difference has enormous political ramifications given vaccines' overall popularity among Americans.
• But it's not yet clear what Kennedy's and the White House's red lines are, or what are his ultimate goals.