Shortly after casting a pivotal vote to advance Robert F. Kennedy Jr.’s nomination for Secretary of Health and Human Services this week, Senator Bill Cassidy (R-La.) took to the Senate floor to explain his decision.

Cassidy, a physician and member of both the Finance and Health, Education, Labor, and Pensions (HELP) committees—where Kennedy’s testimony underwent particular scrutiny—had previously expressed hesitation about the nomination, citing Kennedy’s history of questioning vaccine safety. With the outcome hinging on his support, Cassidy’s vote was seen as critical to moving the process forward.

In his remarks, Cassidy stated that after multiple conversations with Kennedy, he was confident the nominee would “maintain the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices’ recommendations without changes.”

While many following Kennedy’s nomination are familiar with the controversy surrounding his past statements on vaccines, fewer are aware of the Advisory Committee on Immunization Practices (ACIP)—the committee that shapes national vaccine policy and to which Kennedy would have the option of making multiple appointments as Secretary of Health and Human Services. Understanding ACIP’s structure and function is key to appreciating the significance of Cassidy’s statement.

Authority

ACIP was established in March 1964 under Section 222 of the Public Health Service Act (42 U.S.C. §217a), which grants the Secretary of Health and Human Services (HHS) the authority to convene advisory committees with the approval of the President. ACIP provides expert, evidence-based recommendations to the Centers for Disease Control and Prevention (CDC) and the Secretary of HHS on the use of vaccines to prevent and control infectious diseases in the U.S. civilian population. ACIP operates under the Federal Advisory Committee Act of 1972 (FACA) as a federal advisory committee, ensuring transparency and public accountability in its deliberations.

Membership

ACIP comprises up to 19 voting members, including the chair. Members serve in a volunteer capacity and are appointed as Special Government Employees. They are selected for their expertise in immunization practices, public health, vaccine research, and clinical use of vaccines. Preference is given to U.S. citizens. Notably, the committee includes a consumer representative to provide perspectives on social and community aspects of vaccination. An ACIP steering committee reviews applications for membership, and the Secretary of Health and Human Services makes the final selections. ACIP currently has 15 active members, four of whom—including the current chair, Dr. Helen K. Talbot—have terms expiring in June 2025. Given the committee’s 19-member cap, the incoming Secretary of HHS will be able to appoint up to nine members in the next five months.

Committee members must disclose any conflicts of interest and complete an Office of Government Ethics Form 450. In addition, they publicly state any relevant conflicts at the start of each meeting. They are also required to recuse themselves from discussions or votes on matters in which they have a financial or professional interest.

In addition to its voting members, ACIP includes six non-voting ex officio members representing federal agencies such as the Food and Drug Administration and the National Institutes of Health. The committee also comprises non-voting liaison representatives from various professional organizations and academic societies. Current liaison members include representatives from organizations such as the American Academy of Family Physicians, the Pharmaceutical Research and Manufacturers of America, the Society for Healthcare Epidemiology of America, and the National Association of County and City Health Officials.

This diverse composition ensures that ACIP’s vaccine recommendations are informed by a wide range of scientific and public health perspectives.

Meetings and public input

ACIP typically meets three times a year, and its meetings are open to the public and streamed live on the CDC’s website. As noted at its October 2024 meeting, the committee believes, “Engagement with the public and transparency in our processes are vital to the committee’s work.” There are opportunities for individuals to provide input in person or online. Those attending in person may offer comments, though speaking slots are limited to three minutes and are increasingly assigned by lottery due to growing public interest. Written comments can also be submitted through Regulations.gov.

Work Groups

In addition to the general committee, ACIP works through several individual work groups. These include five permanent work groups focused respectively on Adult Immunization, General Recommendations, Child/Adolescent Immunization, Evidence Based Recommendations.

Task-oriented work groups are convened in response to specific needs and disbanded upon completion of their objectives. Work groups are typically formed in response to new data necessitating updates to existing recommendations, anticipated licensure of new vaccines or new indications for existing ones, or the need for regular review of existing ACIP recommendations, which occurs at least every seven years.

There are currently work groups dedicated to combined child/adolescent and adult immunization schedules, COVID-19 vaccines, cytomegalovirus vaccines, human papillomavirus vaccine, influenza vaccines, meningococcal vaccines, Mpox vaccines, pneumococcal vaccines, respiratory syncytial virus vaccines – pediatric/maternal, respiratory syncytial virus vaccines – adult.

Working groups must have a minimum of two ACIP voting members. They may include ACIP ex-officio members and/or ACIP liaison members and a consumer representative. Their work is facilitated by a CDC employee who also served as subject matter expert. Although working groups may invite representatives of pharmaceutical companies to present at meetings, pharmaceutical representatives may not serve as committee members.

Unlike regular ACIP meetings, working group meetings are not open to the public and are conducted under strict guidelines to ensure the confidentiality of any discussions or data reviewed.

Process

The larger committee and individual work groups make recommendations for vaccine use and policy; ACIP members follow a rigorous review process that evaluates vaccine safety, efficacy, and public health impact. Their deliberations also consider disease burden and the feasibility of implementation. They have recently also included health equity.

To ensure transparent and evidence-based decision-making, the committee relies on standardized frameworks such as GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) and ETR (Evidence to Recommendations).

Once ACIP makes a recommendation, the CDC Director reviews it and may approve, amend, or reject it. If approved, the recommendation is published in the Morbidity and Mortality Weekly Report (MMWR), making it the official U.S. immunization guidance.

The Advisory Committee on Immunization Practices (ACIP) classifies its vaccine recommendations into three primary categories:

• Universal recommendations are advised for all individuals within a specific age group, regardless of individual risk factors. For example, the annual influenza vaccine is recommended for everyone six months and older.
• Risk-based recommendations target individuals with specific risk factors that increase their susceptibility to certain diseases. This includes people with certain medical conditions, occupational exposures, or other identified risks. For instance, the hepatitis B vaccine is recommended for healthcare workers and individuals with chronic liver disease.
• Shared clinical decision-making recommendations are specific to cases where a vaccination is not universally recommended for all individuals in a particular age or risk group. Instead, the decision to vaccinate is made collaboratively between the patient and healthcare provider, considering individual circumstances, preferences, and potential benefits. An example is the human papillomavirus (HPV) vaccine for adults aged 27–45 years, where the decision to vaccinate is based on a discussion between the patient and clinician.

ACIP provides detailed immunization schedules tailored to different life stages:

• The Childhood and Adolescent Immunization Schedule covers vaccinations from birth through 18 years, specifying the recommended ages for initial doses and any necessary boosters. It is divided into sections, from birth to 15 months and 18 months to 18 years.
• The Adult Immunization Schedule provides vaccine recommendations for adults aged 19 years and older, including guidelines for those with specific health conditions, occupations, or other risk factors.

A Catch-Up Immunization Schedule also offers guidance for children and adolescents who start late or are more than a month behind in their vaccinations, detailing how to catch up on missed doses.

Individual schedules are regularly updated to reflect new scientific evidence and are designed to optimize protection against vaccine-preventable diseases for all age groups.

Implications of recommendations

ACIP-recommended vaccines are eligible for inclusion in the Vaccines for Children (VFC) Program, which offers publicly funded vaccines at no cost to eligible children. The VFC program ensures that children who might otherwise go unvaccinated—such as those who are uninsured, underinsured, Medicaid-eligible, or Native American/Alaska Native—have access to recommended immunizations without financial barriers.

ACIP’s recommendations also influence vaccine access for adults. Under the Patient Protection and Affordable Care Act (ACA), private health plans are required to cover ACIP-recommended vaccines without cost-sharing when administered by an in-network provider. This first-dollar coverage provision eliminates copays, coinsurance, and deductibles, removing financial barriers that might otherwise deter immunization.