Employees across the massive U.S. Health and Human Services Department received notices Tuesday that their jobs were being eliminated, part of a sweeping overhaul designed to vastly shrink the agencies responsible for protecting and promoting Americans’ health.

The cuts include researchers, scientists, doctors, support staff and senior leaders, leaving the federal government without many of the key experts who have long guided U.S. decisions on medical research, drug approvals and other issues.

“The revolution begins today!” Health Secretary Robert F. Kennedy Jr. wrote on social media as he celebrated the swearing-in of his latest hires: Dr. Jay Bhattacharya, the new director of the National Institutes of Health, and Martin Makary, the new Food and Drug Administration commissioner. Kennedy’s post came just hours after employees began receiving emailed layoff notices. He later wrote “Our hearts go out to those who have lost their jobs” but said that the department needs to be “recalibrated” to emphasize disease prevention.

Kennedy announced a plan last week to remake the department, which, through its agencies, is responsible for tracking health trends and disease outbreaks, conducting and funding medical research, and monitoring the safety of food and medicine, as well as for administering health insurance programs for nearly half the country.

The plan would consolidate agencies that oversee billions of dollars for addiction services and community health centers under a new office called the Administration for a Healthy America.

HHS said layoffs are expected to save $1.8 billion annually — about 0.1% — from the department’s $1.7 trillion budget, most of which is spent on Medicare and Medicaid health insurance coverage for millions of Americans.

The layoffs are expected to shrink HHS to 62,000 positions, lopping off nearly a quarter of its staff — 10,000 jobs through layoffs and another 10,000 workers who took early retirement and voluntary separation offers. Many of the jobs are based in the Washington area, but also in Atlanta, where the U.S. Centers for Disease Control and Prevention is based, and in smaller offices throughout the country.

Some staffers began getting termination notices in their work inboxes at 5 a.m., while others found out their jobs had been eliminated after standing in long lines outside offices in Washington, Maryland and Atlanta to see if their badges still worked. Some gathered at local coffee shops and lunch spots after being turned away, finding out they had been eliminated after decades of service.

One wondered aloud if it was a cruel April Fools’ Day joke.

At the NIH, cuts included at least four directors of the NIH’s 27 institutes and centers who were put on administrative leave, and nearly entire communications staffs were terminated, according to an agency senior leader, speaking on the condition of anonymity to avoid retribution.

An email viewed by The Associated Press shows some senior-level employees of the Bethesda, Maryland, campus who were placed on leave were offered a possible transfer to the Indian Health Service in locations including Alaska and given until the end of Wednesday to respond.

At least nine high-level CDC directors were placed on leave and were also offered reassignments to the Indian Health Service. Some public health experts outside the agency saw it as a bid to get veteran agency leaders to resign.

At the CDC, union officials said programs eliminated because of the layoffs focused on smoking, lead poisoning, gun violence, asthma and air quality, and occupational safety and health.

The entire office that handles Freedom of Information Act requests was shuttered.

Infectious disease programs took a hit, too, including programs that fight outbreaks in other countries and labs focused on HIV and hepatitis in the U.S. and staff trying to eliminate tuberculosis.