More than 8,000 web pages across more than a dozen U.S. government websites have been taken down since Friday afternoon, a New York Times analysis has found, as federal agencies rush to heed President Trump’s orders targeting diversity initiatives and “gender ideology.”

The purges have removed information about vaccines, veterans’ care, hate crimes and scientific research, among many other topics. Doctors, researchers and other professionals often rely on such government data and advisories. Some government agencies appear to have removed entire sections of their websites, while others are missing only a handful of pages.

Among the pages that have been taken down:

• More than 3,000 pages from the Centers for Disease Control and Prevention, including a thousand research articles filed under preventing chronic disease, S.T.D. treatment guidelines, information about Alzheimer’s warning signs, overdose prevention training and vaccine guidelines for pregnant people (the use of the phrase “pregnant people” could have contributed to its removal).

• More than 3,000 pages from the Census Bureau, the vast majority of which are articles filed under research and methodology. Other missing pages include data stewardship policies and documentation for several data sets and surveys.

• More than 1,000 pages from the Office of Justice Programs, including a feature on teenage dating violence and a blog post about grants that have gone toward combating hate crimes.

• More than 200 pages from Head Start, a program for low-income children, including advice on helping families establish routines and videos about preventing postpartum depression.

• More than 180 pages from the Department of Justice, including all state-level hate crime data and seven pages discussing anti-L.G.B.T.Q. hate crimes.

• Close to 150 pages from the Substance Abuse and Mental Health Services Administration, including more than 50 press announcements about the use of the National Disaster Distress Helpline in the aftermath of shootings or natural disasters.

• More than 100 pages from the Food and Drug Administration, including more than 60 regulatory guidelines on topics such as increasing diversity in clinical trials and the potential for addiction and abuse in drug trials.

• Almost 50 research papers from the Office of Scientific and Technical Information. The removed papers span multiple fields, including optics, chemistry and experimental medicine.

• More than 25 pages from the Internal Revenue Service, including the transcript of a video titled “Here’s how to avoid I.R.S. penalties and interest” and the form private schools must submit annually to certify that they have not engaged in racially discriminatory behavior.

• Two dozen research notices from the Nuclear Regulatory Commission — but only notices from the year 2000. Notices from before and after 2000 remain.

• 20 web pages from the National Institute for Science and Technology, including a page detailing the organization’s zero tolerance harassment policy.

• 18 pages from the Health Resources and Services Administration, including a tool kit to care for women with opioid addictions and an FAQ about the Mpox vaccine.

• 18 pages from the U.S. Patent and Trademark Office, including pages about veterans’ innovation and entrepreneurship and a program to teach high schoolers about intellectual property.

• Eight pages from the Department of the Interior, including several detailing environmental policy initiatives (the phrase “environmental justice” may have contributed to the removal of some pages).

• Three pages from the Department of Veterans Affairs: on L.G.B.T.Q. veteran care, minority veteran care and the equity of the Louisiana health care system.

• Two pages from the Marshals Service, one linking to a revision of correctional facility standards and another linking to the department’s fitness readiness program.

Many of the missing pages appeared related to a Trump administration directive — with a deadline of 5 p.m. Friday — to terminate any programs that promote “gender ideology,” and to withdraw documents and any other media that may do so.

In many cases, the removed pages mentioned words like “inclusion” or “transgender.” It is not clear why other pages were removed; how many of the pages will be permanently removed; and how many may be restored with revisions.

And things are still in flux: Since Friday, several pages have gone down and then come back online; others stayed up well past 5 p.m. Friday and were removed only recently. Other government pages, while still accessible, have already been stripped of words related to diversity, gender and climate change, as reported by The Washington Post and others.