Public Health: CDC, Vaccines, and Who Responds to Outbreaks
Key takeaways
- Most public health power belongs to states and about 2,800 local health departments, under the police powers the Constitution leaves to states.
- The CDC tracks diseases, funds state and local health departments, and issues guidance, but it cannot order states to act.
- Vaccine recommendations from the CDC's advisory committee determine which vaccines insurers must cover and which are free for low-income children.
- In 2025 the Health Secretary replaced the entire vaccine committee, and a court stayed its new votes and the 2026 childhood schedule in March 2026.
- The United States had more than 2,200 measles cases in 2025, the most since the early 1990s, and risked losing its measles elimination status.
- The United States formally left the World Health Organization in January 2026.
Public health is the work of preventing disease across a whole population: clean water, safe food, vaccines, disease tracking, and outbreak response. Unlike medical care, it is mostly invisible when it works.
This guide explains who does what, from local health departments to federal agencies, how vaccine policy is set, and the current debates.
When an outbreak begins, local health departments trace contacts and set up clinics, states declare emergencies and request help, and the CDC sends experts and supplies. The HHS preparedness office manages the Strategic National Stockpile, and the HHS Secretary can declare public health emergencies. Measles reached 2,288 cases in 2025, the most since 1991, with continued outbreaks in 2026, and the country faced a review of its elimination status in November 2026. The United States formally left the World Health Organization in January 2026.
The FDA decides whether a vaccine is safe and effective enough to approve, and the CDC's Advisory Committee on Immunization Practices recommends who should get it. Those recommendations set the childhood and adult schedules, require most insurers to cover vaccines at no cost, and determine what the Vaccines for Children program provides free. States decide which vaccines are required for school and what exemptions to allow.
After the COVID pandemic, more than half the states limited the emergency powers of health officials, and trust in public health agencies fell, especially among Republicans. Supporters of the 2025 changes say agencies had become too rigid and too close to drug makers, and that people deserve more choice and transparency about vaccine risks. Most medical and public health organizations say the changes rest on disproven claims, confuse parents, and leave the country more vulnerable to preventable diseases. Debates also continue over funding and over how much power federal agencies should have.
States hold most public health power through their police powers, which let them require vaccines for school, order quarantines, and regulate food and water. About 2,800 local health departments inspect restaurants, investigate outbreaks, and run clinics. Federal agencies fund and support that work, regulate products, and handle threats that cross borders, while tribal health agencies and the Indian Health Service serve Native communities.
The Centers for Disease Control and Prevention in Atlanta tracks diseases, runs labs, sends outbreak experts, and funds state and local health departments. The Food and Drug Administration approves vaccines and drugs and oversees food safety, the NIH funds research, and the Surgeon General leads the Public Health Service Commissioned Corps. In 2025 HHS cut about a quarter of its workforce and reorganized several agencies, and the CDC lost several top leaders.
In June 2025 the HHS Secretary removed all 17 members of the vaccine committee. The new members narrowed COVID vaccine recommendations, dropped the universal hepatitis B birth dose, and backed a revised childhood schedule announced in January 2026. In March 2026 a federal court stayed the appointments, the votes, and the new schedule, mostly restoring the 2025 schedules. Some states and medical groups now issue their own guidance. Separately, the Vaccine Injury Compensation Program pays people injured by vaccines, and proposals to expand it are under review.
See emergency powers in emergency powers explained, health coverage in Medicare, Medicaid, and the ACA, or research funding in who funds science.