Evolution of Vaccine Recommendations in the United States

On June 26, the Advisory Committee on U.S. Vaccination Practices (ACIP) announced new recommendations regarding flu vaccinations that utilize controversial preservatives often misattributed to autism. While this change is unlikely to restrict access to vaccines, it reflects a broader U.S. governmental effort to uphold the integrity of the vaccination recommendation process.

What Changes Have Occurred with ACIP?

ACIP is an advisory body that provides expert recommendations to the U.S. Centers for Disease Control and Prevention (CDC) on vaccinations. Established in 1964, its members are appointed by the Secretary of Health and Human Services, currently Robert F. Kennedy Jr.

Kennedy recently dismissed all 17 members of ACIP, claiming it was necessary to eliminate conflicts of interest. “A complete overhaul is essential to restore public trust in vaccine science,” Kennedy stated in a press release.

This action faced pushback from many public health experts. “Prior to Kennedy’s actions, I had confidence in ACIP. Now, I have none,” remarked Amesh Adalja from Johns Hopkins University. “It’s reckless and dangerous to unilaterally dismantle an entire panel of experts,” added Tinatan, president of the American Infectious Diseases Association, in a statement.

Kennedy appointed eight new members, though one resigned before the inaugural meeting. Several of the new members have raised concerns regarding various vaccines. For instance, Robert Malone, a pioneer in mRNA vaccine technology, discussed on Joe Rogan’s Experience podcast in 2021 the potential links between Covid-19 vaccines and heart-related issues. A 2024 study found that while there was a lower heart attack and stroke rate post-vaccination among approximately 46 million adults, there was an increase in rare side effects such as myocarditis and pericarditis.

A CDC spokesperson stated, “Dr. Malone is a seasoned physician who advocates for rigorous, evidence-based evaluations rather than uncritical acceptance. He does not oppose vaccines based on flawed data or policies—noting the necessity for better information.”

Adalja expressed concerns that some new members lack significant expertise in vaccines, infectious diseases, and epidemiology, suggesting that trust in ACIP under Kennedy’s leadership is dwindling. “In reality, he effectively made ACIP an independent entity,” he stated.

What Changes Have Been Made to Vaccine Recommendations?

In May, Kennedy stated in a video on social media platform X that the CDC would halt Covid-19 vaccine recommendations for most children and pregnant individuals. This decision was taken without ACIP’s input, breaking longstanding precedent.

Subsequently, the CDC revised its Vaccination Guidelines for Children and Adolescents, indicating that decisions regarding Covid-19 vaccinations will be made in consultation with healthcare providers, based on personal preferences.

The new ACIP also voted to discontinue recommendations for flu vaccines containing Thimerosal, a preservative used in several vaccines, during its first meeting. Additionally, the panel advocated for seasonal flu vaccinations for all individuals older than six months.

What is Thimerosal? Is it Safe?

Thimerosal is a preservative used in various vaccines to prevent bacterial contamination and contains trace amounts of mercury, which the body metabolizes into a byproduct known as ethyl mercury.

Ethyl mercury is distinct from the more harmful methylmercury found in certain environmental sources, such as fish. Methylmercury is highly toxic and can accumulate in the body, while numerous studies have shown that low doses of ethyl mercury are safe. Additionally, it is typically cleared from the bloodstream within 30 days, even in infants.

Despite claims from anti-vaccine proponents, no studies have substantiated a link between thimerosal and autism. A 2014 survey of nearly 1.3 million children found no association between vaccines, including thimerosal-containing vaccines, and the development of autism.

The U.S. Food and Drug Administration conducted a thorough review of thimerosal use in pediatric vaccines in 1999, identifying no side effects aside from minor allergic reactions at the injection site.

Which Vaccines Contain Thimerosal?

The utilization of thimerosal in vaccines has decreased as formulations have evolved, with a shift toward single-dose vials minimizing the risk of bacterial contamination.

Thimerosal is not included in routine childhood vaccinations except for certain flu shots, which are used infrequently. For instance, only 3% of children over the age of 65 and about 2% of adults received the flu vaccine containing thimerosal during the 2024-2025 influenza season.

How Will New U.S. Vaccine Policies Compare to Other Countries?

Other nations have continued to recommend thimerosal-containing vaccines. For instance, the UK removed thimerosal from routine vaccinations between 2003 and 2005 to mitigate mercury exposure but later found no evidence of harm. They employed several vaccinations, including those with thimerosal, during specific flu seasons targeting H1N1.

In 1999, the European Medicines Agency endorsed the use of vaccines without thimerosal even in light of no evidence of harm. In 2004, after new data re-affirmed the safety of preservatives, the agency noted that “the benefits of vaccination significantly outweigh any exposure concerns, including thimerosal.” A further review of their guidelines in 2016 reaffirmed their relevance.

Can I Get the Vaccine for Myself or My Child?

Since most seasonal flu vaccinations do not contain thimerosal, it is unlikely that the ACIP’s recommendations will hinder vaccine access. Additionally, the CDC’s updated guidelines regarding Covid-19 vaccines for children and pregnancies should not affect the availability of vaccines.