In 2025, federal health agencies dismantled precedents in vaccine guidance, fracturing state-federal alignment and fueling concerns about public health guidance.
HHS Secretary Robert F. Kennedy Jr. removed all 17 members of the CDC’s Advisory Committee on Immunization Practices in June, citing a need to rebuild public trust. The new panel includes several members with histories of vaccine skepticism. Since the overhaul, the committee has backed a series of changes to longstanding vaccine recommendations, including those for hepatitis B, COVID-19, measles, mumps, rubella and varicella.
In December, President Donald Trump directed HHS and the CDC to review international vaccine schedules, with a goal of aligning U.S. guidance with countries such as Denmark. The review is expected to inform additional changes in 2026 — including potential votes on breaking MMR vaccine into separate shots and further scaling back routine recommendations for children.
After each CDC and FDA move to upend federal vaccine policies, splinters appeared. State health departments and medical organizations embarked on making their own guidelines to differ from the federal government’s recommendations.
This year, U.S. agencies transformed their stances on several vaccines. Here’s a rundown:
HHS pulled preservative in flu shots
In July, Mr. Kennedy signed off on an ACIP recommendation to remove thimerosal from all influenza vaccines. Thimerosal is a mercury-based preservative introduced to flu doses in the 1930s to address bacterial contamination. In 2024, only 4% of flu shots administered in the U.S. contained the preservative.
Florida moved to end school vaccine mandates
In September, Florida health officials said the state will repeal requirements for several school-entry vaccines — including chickenpox, hepatitis B and pneumococcal shots — within 90 days. Other mandates, such as measles and polio, remain in place unless overturned by lawmakers.
Officials initially said they planned to remove these vaccine requirements by early December but they have not materialized.
FDA alters guidance on vaccine coadministration
Vinay Prasad, MD, the FDA’s chief medical and scientific officer and director of its vaccine division, said officials “cannot affirm” the safety and efficacy of coadministering multiple vaccines for COVID-19, flu and other contagious respiratory illnesses. Dr. Prasad’s memo does not prevent clinicians from administering vaccines at the same time, but Pfizer withdrew its guidance that advised coadministration with its COVID-19 vaccine.
CDC trimmed COVID-19 recommendations
On Oct. 6, the CDC revised its immunization schedule to recommend shared clinical decision-making for COVID-19 vaccines, a departure from prior guidance urging universal vaccination for individuals 6 months and older. The change aligns with guidance from the ACIP.
In May, the agency also revoked its recommendation that healthy children and pregnant women receive routine COVID-19 vaccines.
MMRV shot split
In October, the CDC recommended the second varicella dose be administered as a standalone shot, rather than in combination with the trivalent measles, mumps, rubella shot. About 85% of children already receive separate vaccinations, according to NPR.
The change follows a Sept. 18 ACIP vote citing slightly higher seizure risk among toddlers receiving the combined MMRV vaccine. The panel also voted to exclude the combination shot from federal coverage under the Vaccines for Children program.
President Trump and Deputy HHS Secretary Jim O’Neill have both called on manufacturers to split MMR vaccines into three separate shots, but no official agency action has been taken to do so.
FDA proposed overhaul of vaccine approval process
In another memo, Dr. Prasad called for longer clinical trials and stricter efficacy standards, including for routine updates like the annual flu shot. The proposal, prompted by an internal memo citing 10 pediatric deaths linked to COVID-19 vaccination, drew criticism for lacking transparency and risking public confidence in federal healthcare authorities.
CDC ended 34-year position on hepatitis B vaccines
Breaking from a position it held since 1991, the CDC said Dec. 16 it recommends shared decision-making between parents and clinicians on whether to administer the first hepatitis B vaccine to infants whose mothers test negative for the virus.
The CDC’s vaccine series, historically, advised the first hepatitis B dose within 24 hours of birth, at hospital discharge or when the infant is 1 month old. The second dose is recommended for infants between 1 and 2 months old, and a third dose between 6 and 15 months old.
