Upheaval at ACIP: A Timeline of U.S. Vaccine Policy and Leadership Shifts

Over the past year, the CDC’s Advisory Committee on Immunization Practices (ACIP) has undergone sweeping changes to its leadership, membership, review processes, and recommendations. These shifts are transforming how vaccines are reviewed and recommended in the U.S. — and fueling confusion, distrust, and growing public backlash.

Now, a recent federal court ruling has paused some of these changes – while also raising new questions about what comes next. With ACIP’s role, structure, and authority in flux, the need for stable, credible, independent guidance has become more urgent than ever.

This timeline tracks key moments shaping the committee and U.S. vaccine guidance over the past year.

A Timeline of Changes at ACIP

February 2025: ACIP’s first scheduled meeting of the year was abruptly postponed after the agenda and public comment window had already opened. Independent experts and medical groups warned the delay signaled possible political interference in what had long been a technical, science-driven process.

April 15-16, 2025: ACIP held its postponed February meeting with the original membership still intact, and workgroups presented their evidence reviews as planned.

June 9, 2025: HHS Secretary Robert F. Kennedy Jr. dismissed all 17 sitting ACIP members, an unprecedented move in the committee’s history that drew widespread criticism from major medical and public health organizations, including the American Medical Association (AMA). The Secretary cited conflicts of interest as the rationale for the wholesale firings, but a thorough analysis published in JAMA in August 2025 found conflicts of interest on ACIP were already rare. By 2024, only about 5% of members reported any financial conflict at a given meeting, and fewer than 1% received personal income from vaccine companies.

Before the overhaul, ACIP membership typically required years of service on subcommittees, a formal nomination process, and extensive conflict-of-interest review.

June 11, 2025: Kennedy appointed eight new ACIP members just days after the mass firings, bypassing the traditional multi-year vetting process. Critics argued the new structure made the committee less transparent and more ideologically skewed.

Among those appointed were biostatistician Martin Kulldorff – who has repeatedly questioned Covid-19 vaccination policies – and vaccinologist Robert Malone, who has been widely criticized for spreading misleading claims about mRNA vaccines. Kulldorff was named ACIP chair.

July 23, 2025: ACIP voted to remove all thimerosal-containing influenza vaccines from its recommendations. Public health experts widely criticized the move as unnecessary because nearly all U.S. flu shots already lacked thimerosal. The change primarily affected about 4% of multi-dose vials used in some rural and medically underserved areas, where mass inoculation events help protect vulnerable populations, like nursing home residents.

August 1, 2025: Thirty non-voting liaison organizations — including major medical societies — were removed from ACIP workgroups. Historically, these groups provided expertise and stakeholder input during deliberations.

Groups such as the American College of Obstetricians and Gynecologists (ACOG) and the American Academy of Pediatrics (AAP) later distanced themselves from the committee, citing concerns about transparency and scientific integrity in the ACIP process.

Sept. 15, 2025: Seven additional members were appointed to ACIP, including several individuals with histories of opposing vaccine guidance. For example, pediatric cardiologist Kirk Milhoan repeatedly downplayed the benefits of Covid‑19 vaccination for children and highlighted what he described as serious, under‑recognized heart risks from mRNA shots. [CD2] Epidemiologist Catherine Stein publicly opposed university vaccine mandates and aligned herself with groups resisting Covid‑19 public health measures.

Sept. 18-19, 2025: ACIP changed several vaccine recommendations. The combined measles-mumps-rubella-varicella (MMRV) vaccine was no longer recommended for children under 4. The committee also moved Covid-19 vaccination guidance to “individual decision-making” rather than a universal recommendation for anyone, a shift experts warned could confuse clinicians and complicate insurance coverage and pharmacy access for individuals wanting these vaccinations.

Dec. 1, 2025: Milhoan took over as chair of ACIP after Kulldorff moved to a senior leadership role at HHS.

Dec. 4-5, 2025: ACIP removed the universal recommendation for newborns to receive the hepatitis B vaccine at birth. Experts warned the change could increase risk because infants can be exposed to hepatitis B through contact with caregivers or relatives long before infection is detected.

The universal birth dose gives every newborn a baseline layer of protection before everyday exposures begin, which is why many pediatric and infectious disease experts continue to support routine universal vaccination within 24 hours of birth. Since the universal birth dose of the hepatitis B vaccine was introduced in 1991, pediatric cases have dropped by about 99%, with no evidence that delaying the first dose improve safety or effectiveness.

Jan. 5, 2026: The CDC released a revised childhood immunization schedule without a formal ACIP vote, a significant departure from past practice. The new schedule reduced routine recommendations from 13 vaccines targeting 17 diseases to 7 vaccines targeting 11 diseases.

Universal recommendations were removed for Covid-19, hepatitis A, hepatitis B, influenza, rotavirus, and meningococcal ACWY vaccines.

Officials cited Denmark’s vaccine schedule as a model, but critics noted the comparison is misleading. Denmark has different disease patterns, higher vaccination coverage, and a stronger primary-care safety net than the United States. Moreover, other comparable countries, including Australia, Japan, and Canada, have vaccine recommendations similar to the U.S.

Jan. 23, 2026: Milhoan appeared on the “Why Should I Trust You?” podcast, expressing doubts about the necessity of the polio and measles vaccines, which he suggested should be optional.

Feb. 18, 2026: After failing to publish an agenda or open public comment, ACIP postponed its Feb. 25-27 meeting to March 18-19.

Mar. 16, 2026: A federal judge blocked changes to vaccine recommendations and ACIP membership while litigation continues. The decision prevented ACIP from meeting March 18-19. HHS is likely to appeal.

The postponed March meeting was expected to focus heavily on Covid-19 “vaccine injuries.” Public health experts note that evaluating legal claims related to rare vaccine side effects is the role of federal injury-compensation programs – not ACIP. They warn that turning the committee into a forum for debating vaccine harms risks confusing families and undermining confidence in vaccines that remain safe and effective.

While the ruling stops further changes for now, it leaves unresolved questions about ACIP’s future structure and function. Restoring stable, transparent, and science-driven decision-making will be critical to rebuilding America’s trust.