A U.S. federal judge on March 16 issued an order blocking central aspects of Health Secretary Robert F. Kennedy Jr.'s initiatives to alter national vaccine policy, including plans to pare back the number of vaccinations routinely recommended for children. U.S. District Judge Brian Murphy in Boston ruled partly in favor of medical organizations that challenged the changes as unlawful and said the policy shifts would damage vaccination uptake and public health.
Below is a chronological account of vaccine-related policy moves and regulatory actions taken under Kennedy's stewardship as described in public announcements and agency statements. Each entry lists the date of announcement followed by the details provided by federal agencies and officials.
FDA Recommendations for Influenza Vaccines
- Date of Announcement: March 13, 2025
- Details: The U.S. Food and Drug Administration independently selected the viral strains for the 2025-26 influenza vaccines after canceling a planned independent advisory committee meeting. The agency issued its strain recommendations following a closed-door inter-agency review rather than the originally scheduled public advisory process.
Environmental Toxin Studies Related to Autism
- Date of Announcement: April 16, 2025
- Details: The health secretary announced plans for a series of studies to examine potential links between autism and environmental factors such as mold, air, water and food. Kennedy asserted, without any scientific evidence, that "environmental toxins" are responsible for the rise in autism rates among U.S. children.
Launch of U.S. Autism Project Using Medicare and Medicaid Data
- Date of Announcement: May 7, 2025
- Details: Federal agencies said they would establish a database drawing on Medicare and Medicaid records to study causes of autism. The effort was described as part of a broader initiative to investigate potential links between vaccines and autism, a connection Kennedy has previously promoted contrary to scientific evidence.
FDA Tightens Requirements for COVID-19 Vaccine
- Date of Announcement: May 20, 2025
- Details: The FDA announced plans for new clinical trials for annual COVID-19 booster shots, restricting booster recommendations primarily to older adults and individuals at higher risk for severe disease. The agency framed this change as aligning the United States with international approaches to COVID vaccination.
U.S. Drops COVID Vaccine Recommendation for Healthy Children and Pregnant Women
- Date of Announcement: May 27, 2025
- Details: Federal guidance was changed so that routine COVID vaccinations were no longer recommended for pregnant women and healthy children. The decision bypassed the typical advisory process at the Centers for Disease Control and Prevention and drew criticism from numerous medical organizations.
Cancellation of Moderna Bird Flu Vaccine Contract
- Date of Announcement: May 28, 2025
- Details: The administration canceled a contract with Moderna for late-stage development of a bird flu vaccine amid a domestic outbreak, stating that the program did not meet scientific standards.
Kennedy Removes Vaccine Advisory Committee Members
- Date of Announcement: June 9, 2025
- Details: Kennedy dismissed all members of the CDC's expert vaccine advisory panel, which is tasked with recommending vaccine use and target groups. The action was presented as an effort to restore public trust in health agencies, while scientists and experts warned that the move risked undermining confidence in public health institutions.
Kennedy Names Replacement Members to CDC Panel
- Date of Announcement: June 11, 2025
- Details: Two days after firing the existing advisory committee, Kennedy appointed eight new members to the CDC's key vaccine advisory panel. Several of the new appointees had publicly advocated against vaccines.
Vaccine Panel Recommends Removing Thimerosal from U.S. Flu Shots; Kennedy Accepts
- Date of Announcement: July 23, 2025
- Details: Kennedy accepted a recommendation from the hand-picked vaccine panel to stop distributing influenza vaccines that contain thimerosal, a mercury-based preservative used to prevent contamination in multi-dose vials. Major health authorities have previously deemed thimerosal safe.
CDC Excludes Experts from Panels That Develop Vaccine Policy
- Date of Report: July 31, 2025
- Details: The CDC informed physician groups, public health professionals and infectious disease experts that they would no longer be invited to help review vaccine data and develop recommendations.
HHS to Wind Down mRNA Vaccine Development
- Date of Announcement: August 8, 2025
- Details: The U.S. Department of Health and Human Services said it would wind down mRNA vaccine development activities within its biomedical research unit. The mRNA platform was the foundation for the COVID-19 vaccines used during the pandemic.
U.S. Orders Vaxart to Halt COVID Trial Because of mRNA Wind Down
- Date of Announcement: August 13, 2025
- Details: Vaxart reported receiving an order to stop screening and enrollment for its mid-stage trial of a next-generation COVID-19 vaccine, citing the broader wind-down of government support for mRNA vaccine work. Vaxart had been awarded up to $453 million by the government in 2024 to study its vaccine.
CDC Taps Vaccine Skeptic to Lead COVID Committee
- Date of Announcement: August 25, 2025
- Details: The CDC selected Retsef Levi, a member of its key vaccine panel, to chair its COVID-19 immunization working group. A health department spokesperson told Reuters that Levi had criticized mRNA vaccines, asserting they can cause serious harm and death particularly among children and had called for their withdrawal. The working group evaluates data and scientific evidence on COVID vaccines to develop policy options for the advisory committee whose recommendations inform the CDC director.
FDA Narrows Under-65 COVID Vaccine Eligibility; Maintains Access for Older Adults
- Date of Announcement: August 27, 2025
- Details: The FDA authorized updated COVID-19 vaccines for everyone over age 65 while narrowing recommendations for younger populations to those with health risks. The agency also rescinded the emergency use authorization for Pfizer's vaccine in children under age 5, leaving only Moderna's shot authorized for children aged 6 months through 4 years; both vaccines referenced use mRNA technology.
CDC Director Fired After Vaccine Policy Clash
- Date of Announcement: August 28, 2025
- Details: CDC Director Susan Monarez was dismissed after opposing vaccine policy changes promoted by Kennedy that she believed ran counter to scientific evidence. Monarez later said she was pressured to endorse decisions of Kennedy's hand-picked advisory committee and described her removal as part of an effort to weaken U.S. vaccine standards.
Revamped CDC Vaccine Panel Meeting Scheduled
- Date of Announcement: September 2, 2025
- Details: The reconstituted CDC vaccine advisory committee was set to meet on September 18, with potential votes on recommendations for hepatitis B, measles-mumps-rubella-varicella, and respiratory syncytial virus vaccines, according to the Federal Register.
Kennedy Appoints Seven New Members to CDC Vaccine Panel
- Date of Announcement: September 3, 2025
- Details: An internal CDC document indicated that Kennedy designated seven new members for the Advisory Committee on Immunization Practices panel.
FDA Launches Fresh Safety Scrutiny of Approved RSV Therapies for Infants
- Date of Announcement: December 9, 2025
- Details: U.S. regulators informed senior executives at Merck, Sanofi and AstraZeneca that their approved infant RSV preventative therapies would undergo renewed safety reviews following concerns raised by vaccine skeptics.
U.S. Drops Universal Childhood Recommendations for Several Vaccines
- Date of Announcement: January 5, 2026
- Details: The United States ended longstanding universal guidance recommending that children receive influenza, rotavirus, meningococcal and hepatitis A vaccines, changing these to a shared clinical decision-making approach. The change was approved by Acting CDC Director Jim O'Neill without the agency's usual external expert review.
FDA Reverses Course on Moderna Flu Vaccine Application
- Date of Announcement: February 18, 2026
- Details: Moderna stated that the FDA initially refused to review its application for a new influenza vaccine but then agreed to accept a revised submission a week after the refusal. The sequence of refusal followed by rapid reversal heightened concerns about shifting vaccine policy and regulatory scrutiny of mRNA-based products under the administration.
This timeline captures decisions announced publicly and actions taken by federal agencies relevant to vaccine policy under the leadership of the health secretary. The court ruling issued on March 16 temporarily blocks key elements of these policy changes, including moves that would reduce routine vaccination recommendations for children. The judge's decision followed arguments from medical groups that the moves were unlawful and would harm vaccination rates and public health.
Readers should note that this account is a chronology of announcements and agency statements. It does not attempt to adjudicate the underlying scientific debates or to provide independent conclusions beyond the documented actions and dates listed above.