After the latest round of mass firings at the Centers for Disease Control and Prevention over the weekend, the union that represents agency employees estimates that around 3,000 people this year—about a quarter of the agency’s workforce—have departed the agency.

That number includes workers affected by layoffs earlier this year, as well those who have accepted the Trump administration’s “Fork in the Road” buyout program.

The most recent cuts came down amidst the ongoing government shutdown. On October 10, more than 1,300 CDC employees received termination notices. Soon after, however, about 700 of those people were told via email that they were mistakenly terminated and were not in fact subject to the reduction in force. An estimated 600 people remain terminated.

An additional 1,300 CDC employees are, according to the union, on administrative leave and being paid but not working.

The Trump administration has not shared official numbers of those targeted by the reductions. The estimate was compiled by the American Federation of Government Employees (AFGE) Local 2883, which represents CDC workers.

The current round of reductions affects the National Center for Chronic Disease Prevention and Health Promotion, National Center for Health Statistics, the CDC library, the agency’s human resources department, campus safety staff, as well as the CDC’s office in Washington, DC, which acts as a liaison to Congress and provides public health information to policy makers.

“All HHS employees receiving reduction-in-force notices were designated non-essential by their respective divisions,” Andrew Nixon, director of communication at the Department of Health and Human Services, told WIRED via email.

Among those reinstated include staff that publish the agency’s flagship publication, the Morbidity and Mortality Weekly Report, as well as leadership in the National Center for Immunization and Respiratory Diseases and National Center for Emerging and Zoonotic Infectious Diseases, according to AFGE. Members of the Epidemic Intelligence Service, the CDC’s “disease detectives” unit, were also brought back.

The CDC has been in turmoil since HHS secretary Robert F. Kennedy Jr. took office in February. In addition to carrying out mass layoffs, Kennedy is attempting to upend established vaccine policy. Earlier this year, he removed all 17 sitting members of a federal vaccine advisory committee, replacing them with members of his choosing. Several are vaccine skeptics and have been critical of public health measures taken during the Covid-19 pandemic.

In August, Kennedy fired CDC director Susan Monarez, who had been in the position for just a month. Monarez told a Senate committee in September that Kennedy demanded she sign off on new vaccine recommendations “regardless of the scientific evidence” and dismiss career officials without cause. During her short time at CDC, a gunman opened fire on the agency’s Atlanta campus and killed a police officer who responded to the shooting.

The shooter allegedly targeted the CDC because he blamed the Covid-19 vaccine for making him sick and depressed.

In the wake of Monarez’s departure, several senior CDC officials resigned including Demetre Daskalakis, director of the National Center for Immunization and Respiratory Diseases. Debra Houry, chief medical officer and deputy director for program and science, and Daniel Jernigan, director of the National Center for Emerging and Zoonotic Infectious Diseases, also stepped down.

“There are very few people left in leadership at the agency. We know that at the highest level of leadership in the CDC, there are no public health or medical professionals left to help guide CDC recommendations,” says Abby Tighe, executive director of the National Public Health Coalition, formerly Fired but Fighting, a network of current and former professionals from the HHS. Tighe was among those laid off from CDC earlier this year.

The AFGE represents hundreds of thousands of federal employees, and is demanding that all notices be rescinded immediately. It’s standard for federal agencies to inform the union about a reduction in force. AFGE says it has not received that notice from the Trump administration.

Yolanda Jacobs, president of AFGE Local 2883 calls the CDC firings “illegal” and “callous.”

“Many of these cuts have been made without sufficient explanation to understand the reasoning behind them,” says John Brooks, former chief medical officer of CDC’s division of HIV/AIDS intervention, who retired last year.